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15620 75TH PL W.PDF111111111111 6044 15620 75TH PL W ADDRESS- TAX ACCOUNT/PARCEL NUMBER: OD ,573 I 0 Z T�l 00 BUILDING PERMIT (NEW STRUCTURE): ` �? " 02 J / COVENANTS (RECORDED) FOR: 1fAxm/tsr #'7SaS220363 CRITICAL AREAS:- 1� J 6 DETERMINATION: ❑ Conditional Waiver ❑ Study Required gwliver DISCRETIONARY PERMIT #'S: V 377/-/ DRAINAGE PLAN DATED: g /Z-9-3 PARKING AGREEMENTS DA EASEMENT(S) RECORDED PERMITS (OTHER): foia7os Tlwe o ,l�/L•4��✓ PLANNING DATA CHECKLIST DATED SCALED PLOT PLAN DATED: -4 131 SEWER LID FEE S: LID #: 2-10 SHORT PLAT FILE: LOT: l BLOCK: 2-0 SIDE SEWER AS BUILT DATED: (a SIDE SEWER PERMITS) #:_ - Le �� 4s� GEOTECH REPORT DATED: l 26 STREET USE / ENCROACHMENT PERMIT #: FOR: WATER METER TAP CARD DA OTHER: 3--Z 1-9, J ,fezl3 06 40/ VIIIOVKle-f jit'o'n- col--tolek .4-aexm1179e-(o4-c/ LATEMP\DSTs\Forms\Street File Checklist-doc B.N. RAIL Roan R/\J ._ L"IG.S1' G`I�o'f o9' R.595EAo .. 3- 4 'I5t` ftxe Wes r �R . i G�.a�` g c� xP.wo�o>fD �F Yr PfIt r ^,�SnO - �� c" ] .�c "S •ea�eeae�Z � �.T _v "P�D A6 'gti P K r r s g u ^ C v � 1 x Z GN 0 IL G) � 8O Q \ B z o , O�IR 7S„�➢ „ o z i)��n cl r 1, Y COPY SHANAbN ON, IN • Fes/; .?r rr r,n [�h 1 1 I. 11WANK!', UAINI LUUN October 17, 1994 1 64 Ms. Ursula Schluter 21701 80th Avenue West, #4 � ii)E, Pr,�j Edmonds, Washington 98020 RE: INSTALLATION OF DRAINAGE SYSTEMp PROPOSED RESIDENCE, 15620 75TIl PLACE WEST, EDMONDSt WASHING ON As we have discussed, it is our recommendation that the proposed trench subdrain system for your proposed residence at 15620 75th Place West in Edmonds, Washington, be installed as soon as possible. It has been a dry summer and there has been little rain so far this fall. As a result, groundwater levels are still very low and conditions are good for installation of the drain. We highly recommend that the drain be installed in the next few weeks if possible. Having the drain in place over the winter months will increase the stability of the site and will greatly facilitate the remaining construction next spring. It will also give its a chance to evaluate its effectiveness through a winter season. We appreciate the opportunity to be of service. Sincerely, SHANNON & WILSON, INC:. Ralph N. Boirum. P.H. Senior Associate RNB:TEK/rnb cc: City of Edmonds, Ms. Jeannine L. Graf W 6114-02 wel N. MCNwNtsrrdis�'".Slflrre Inn I �t;r'. n()X 3UU3U;3 SEATTI_E, WASHINGTON 1A)1():) F-0d Wder:v b66T eT'7�o0 Tseo ZZ9 sim : 'ON dNOHd aginIHOS uinsNn NOISBC-iHnsIn : woad Ms. Ursula Schlutgo 217'0l 801h Mrtnu t, N4 >, r Edmonds, N%hington 98020 • RE; MONrMRI i•G OF SUBDPAIN MS'TALL.A'TION, MPOMM RtSIDENCE, 15620 75TIK PLACE WEST, EDMONDS, WAf3K NL'TON MMMiT NO 940703 !hear Ms. 9shultev. Between October 21 and October 27, 1994, we made several visits to the site to monitor tho Installation of the trench subdrain at youe proposed residenow at 15620 75th Ptwe West In Edmonds, Washington. The drains cemsisted of slotted, plastic pipe installed in the bottom of gravel filled trenches at wlected locations to intercept and remove groundwater from the site. The work was done by North Coast Construction. At our woinmendation, two drain lines wem installed: one was ]sang! in the storm water detention eteevstion, approximately 2 fbtt below the sWrm water detention pipe,, the second extends up the slope slang the south property tine and crosm the Rita pal• 91 to the elope Contours, hetween the pnopeied foundation pile locations (tap be installed in the spring of 199.1). Roth drttlaW trenches flow to the [ewer catch basin along the south Bide of the property. Groundwater was present in the trench excavations, partioulttrly in the vicinity of the storm water detention system, %ter was flowing from the twmpleted subdrain system at a tote of 4 to S gallons per minute on C*Wbw 29, 1994..Native vines and straw wow spread aema the rite as erosion pivto-Won following completion of the earthwork. *M N0rlrl l ,1471 { 3TMtltt •ouiTc ux; M.).1IOX 0103 AM-Ki2,11C20 MX�P.Cxtl.1339.87/1 owus (90u) XVd i•090-L6 (800 SZON VN18aNONOW to'M 3r1N3Mr KLOO Wta t191,C1imog rIf19unmema 1VASIA W-3385.02 =%MNQ�0 aS's21d'XVJ S HL R M $Y421110 id ANV 3AVH naA tit - 3Eri1933W MOUA .133HSa3A03 xV:J .N'E)iSB ] ibn'sln -- 70(y :ol Alum 3V4V41 WHA1130 TOd WdZO'6 tr66T LT'^ON TSW ZL9 90E , 'ON 3NDHd a3in-i�os t nr son ND SM -bnS I A woe j -,--From : VISUAL DESIGN URSULA UTER PHONE No. : 206 672 0651 • Nov.17 1994 9:03PM P01 - M a Ms. Ursula Schluter Novembo r 15, 1994 Page 2 SHANNO►N MMI SON, INC. Bamd on our obscryations at the site, it is our opinion that the %ork was accomplished in a►eaordanac with our rwommendations and the approved plane and apecidoations, We appreciate the opportunity to be of service, Sincerely, SNANNQN & WTTSON, TKC , Ralph N. Boirum, P.B. Staff Consultant RNB:TEIK/rnb W3385.42XWfW33854kdf1W W-5385-42 • '^+�� 3 r � LGVQL - NOl ON14dGVM O��h a'1; 76 a�nA q,L an ao5i SyayaLNl/ay/11'7aLIHy1V Nmolt9 "l JI"1'1141d �Z�iL YM 'SOMMtt7 n arry yrSL- oz ^si v�Lmuos v-Insvn you x�Naolcav MAN d o will oII(l�'I•' ----- e - r• �3 C � ♦cyvato,* � 8 e �aCll Yd3�S�� 1_ ?vaz LS•y .IA Eo.I• V .Ls'oL-� -. tAIV orov"iMy -N-g 0 .j -J- W F- CITY OF EDMONDS Address of Construction: Property Legal Description (Include all easements): diz wtl 4 SIDE SEWER PERMIT PERMIT tNE Owner and/or Contractor: 6&Su s\;!�r7 �� Zs.JG-aCb6i7 State License No. -9GO Sp Building Permit No. q-,52- -� R F. CEwEL� K Single Family ❑ Multi -Family (No. of Units ) ❑ Commercial ❑ Public Invasion into City Right -of -Way: &No MCI y 19" RW Construction Permit No.plORKS DEPI Cross other Private Property:§9LNo ❑ Yes Attach legal description and copy of recorded easement I certify that I ha4 read andishall comply with all city requirements as indicated on the back of the Permit Card. ---"/-/9-� Date * CALL DIAL -A -DIG (1-800-424-5555) BEFORE ANY EXCAVATION * OFFICE USE ONLY * FOR INSPECTION CALL 771-81M, PUBLIC WO KS DEPT. �f 0-5735— Permit Fee: �0 Issued By Trunk Charge: �� Date Issued: Assessment Fee: �/A Receipt No.: , Lid No.: 21,0 Partial Inspection: Date Initial Comments Reason Rejected: Date Initial Final Inspection Approved: Date ' -S__�5Initial�� ** PERMIT MUST BE POSTED ON JOB SITE ** White Copy: File Green Copy: Inspector Buff Copy: Applicant Revised 3 90 • O n v a �n a M j l I � !2 --1 R a P. w 04 G il C4 I 3 J a. 00 w u� C 0 0 0 a r CITY OI, L DMONDS GRINDEN PUMP'S NAME � �J�� {�}t �,^ `I'ELLPHONE NUMBFR (�?�' % ADDRESS 1 �j' CQ Z o % 5?A (' S 390 -- aN Su PERMIT NO. Oo,1riLity Item -- _ _ Unit Total Cost Cost 2 11 MA.IPT. Piastxe A6ap. $ 6.68 ea. $ 13.36 1 1� x 1 bbcl.1 ret]. 5.70 ea. 5.7U 1 1 a" ,lobe cripple 3.09 ea. 3.09 A 1:?" St.,OL. clamps .65 ea. 2.60 1 6" x 11" Y.V.C. Plug 22.87 22.87 D 1TI', RECEIVED: 7 �S Kc;�NnF' ZOd WLie :TT S66I ZZ'- TTTOZVL : 'ON 3NOHd ONI JNIawn-id Hsu : woad City of Edmonds Critical Areas Determination Applicant: Ursula Schluter Determination #: CA-93-10 Project Name: Permit Number: Site Location: 15620 75th Pl. W. Property Tax Acct #: 5131-028-001-001 Project Description: New Single Family Residence Waiver Criteria (all criteria must be found to apply): XX There will be no alteration of the Critical Area or its required buffers; XX The development proposal will not impact the Critical Area in a manner contrary to the goals, purposes, objectives and requirements of the Critical Areas ordinance; XX The development proposal meets the minimum standards of the Critical Areas ordinance; XX The above findings are based on the following conditions of approval: 1. The Applicant/property owner must follow the requirements of the Steep Slope, Landslide Hazard Ordinance (ECDC § 19.05 2. The above condition in no way exempts or waives any other requirement, condition, code, ordinance or law. Based on the above findings and conditions, the requirement for a Critical Areas Study associated with this development permit is hereby Waived, as authorized by Chapter 20.15B.150 (B) of the Edmonds Community Development Code. Name ignature Date City of Edmonds Critical Areas Checklist The Critical Areas Checklist contained on this form is to be filled out by any person Preparing a Development permit Application for the City of Edmonds prior to his/her submittal of a development permit to the City. The purpose of the Checklist is to enable City staff to determine whether any potential (critical Areas are or may be present on the subject property. The information needed to complete the Checklist should be easily available from observations of the site or data available at City Hall (Critical Areas inventories, maps, or soil surveys). An applicant, or his/her representative, must fill out the checklist, sign and date it, and submit it to the City_ The City will review the checklist, make a precursory site visit, and make a determination of the subsequent steps necessary to complete a development permit application. With a signed copy of this form, the applicant should also submit a vicinity map Of the parCel with enough detail that City staff can find and identify the subject parcel(s). In addition, the applicant is encouraged to include any other pertinent information or studies in conjunction with this Checklist to assist staff in completing their preliminary assessment of the site. I have completed the attached Critical Area Checklist and attest that the answers provided -are factual, to the best of my knowledge (fill out the appropriate column below). Owner / Applicant: Name lit 'V log _W .. Title Street Address �JW10`Lds &Ippa iIA9W City, State, ZIP to Ja, Phone - g3 Signature Date Applicant Representative: Name Title Street Address City, State, ZIP Phone Signature Date STREET FiLL. t. + W-6114-02 Revised Geotec Iiii°Report Proposed Residence at Lots 1 and 2, 75th Place West Edmonds, Washington January 1994 Ms. Ursua/ Schluter 21701 80th Avenue West, #4 Edmonds, Washington 98020 SHANNON 6WILSON, INC. GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS 400 N 34th St a S ite 100 U P.O. Box 300303 Seattle, Washington 98103 206-632.8020 • SHANNON 6WIL.SON, INC. • SEATTLE ®11' FHANFORD AIRBANKKS ® GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS ANCHORAGE SAINT LOUIS BOSTON January 26, 1994 ' 9%4 Ms. Ursula Schluter 21701 80th Avenue West, #4 Edmonds, Washington 98020 RE: REVISED GEOTECHNICAL REPORT, PROPOSED RESIDENCE AT LOTS 1 AND 2, 75TH PLACE WEST, EDMONDS, WASHINGTON This report presents the results of our geotechnical reconnaissance, subsurface explorations and engineering analyses for your proposed residence on 75th Place West in Edmonds, Washington. This report is a revision of our previous report dated March 29, 1990 and presents additional information for site development and the results of a recently completed subsurface exploration at the site. The purpose of our work was to evaluate the site and provide recommendations to aid in foundation design for the proposed single-family residence. Our work included a reconnaissance of the site, review of our previous work and existing geotechnical reports, and completion of an exploratory soil boring at the site. SITE AND PROJECT DESCRIPTION The property is located on the west side of 75th Place West in the Meadowdale area of Edmonds, Washington. The property measures approximately 97 feet by 190 feet and consists of two lots located about 200 feet north of the intersection of 75th Place West and 158th Street S.W. The legal description for the property is: lots 1 & 2, Block 28, Meadowdale Beach, Snohomish County, Washington. The lots are bordered on the east by 75th Place West and on the west by the Burlington Northern Railroad right-of-way. The property is shown on the Site Plan, Figure 1. An occupied lot lies to the south of the subject property and a lot with an abandoned house and shed lies to the north. Portions of the abandoned structures which lie on the lot to the north protrude into the subject property. The ground surface is covered with dense brush and blackberry vines. The site slopes moderately downward from 75th Place West to the BNRR tracks. The average slope is about 1 vertical to 3 horizontal (1V to 3H). A retaining wall about 4 feet high has been built by the railroad along the toe of the slope. We understand this wall was constructed to prevent debris from sliding onto the railroad right-of-way. W-5385-02 400 NORTH 34TH STREET -SUITE 100 F.O. BOX 300303 SEATTLE. WASHINGTON 98103 206.632.8020 FAX206.633.6777 Ms. Ursula Schluter SHANNON 6WILSON, INC. January 26, 1994 Page 2 We understand that the proposed residence will be a multi -story, single-family house. A garage and elevated driveway between the house and road will also be constructed. The dimensions of the proposed house are approximately 61 feet long by 48 feet wide. The approximate location of the house is as indicated on the Site Plan, Figure 1. SUBSURFACE EXPLORATIONS The site was explored by means of one soil boring drilled on the east side of the site, as shown on the Site Plan, Figure 1. The location of the boring was obtained by tape measurement from existing features. The boring was drilled to a depth of 61.5 feet . A log of the boring is presented on Figure 3. The soil boring was drilled by Associated Drilling Co. of Seattle under subcontract to Shannon & Wilson, Inc. on November 19, 1993. A truck mounted B-61 drill rig equipped with a 3-3/8-inch I.D. hollow -stem auger was used. Standard Penetration tests were performed at 2.5-foot intervals to a depth of 20 feet and at 5-foot intervals thereafter. The Standard Penetration test consists of driving a 2-inch O.D. split -spoon sampler a distance of 18 inches into the bottom of the borehole with a 140-pound hammer falling 30 inches. The number of blows required to drive the sampler each of three 6-inch increments was recorded, and number of blows required to cause the last 12 inches of penetration is termed the Standard Penetration Resistance (N-value). This value is an indicator of the relative density or consistency of the soils. Samples obtained in the field were classified by a geologist, sealed in jars, and returned to our laboratory where the classification of each sample was visually. checked and its moisture content was determined. The results of the Standard Penetration Tests, moisture contents and soil classifications are summarized on the boring log, Figure 3. In addition to the recent soil boring, subsurface explorations were completed by Earth Sciences in February 1986. Test pits TP-2 and TP-3 of the Earth Sciences report were located on the Schluter property (previously the Hodge property). The results of their test pit explorations are presented in Figure 7 and their approximate locations are shown in Figure 1. W-5385-02 Ms. Ursula Schluter !RNNON 6WILSON, INC. January 26, 1994 Page 3 SUBSURFACE CONDITIONS �J The subsurface conditions at the site are illustrated on the attached Section A -A', Figure 2. The results of the explorations indicate that the site is generally underlain by 8 to 21 feet of slide debris consisting of loose sand, silt, and silty clay. Below the slide debris the soils consist of stiff to very stiff, fine -sandy silt and clayey silt, becoming hard to very stiff silty clay. The stiff to hard silt and clay appears to be glacially consolidated. Considerable groundwater seepage was observed on the surface of the site during our reconnaissance. Seepage was observed during drilling of boring B-1 at a depth of 18 feet. Groundwater flow was also noted on the test pit logs in the report by Earth Sciences. LANDSLIDE HISTORY The Schluter property lies within the Meadowdale landslide complex. Roger Lowe Associates prepared a report titled, "Landslide Hazards Investigation, Meadowdale Area, Edmonds, Washington" in 1979. This report details the geologic history, site geology, and landslide history of the Meadowdale Landslide Complex. According to the above report, the subject area experienced large-scale ground movement two to three thousand years ago. This slide was 3,200 feet long and as much as 650 feet wide. The head scarp is easily distinguished above 75th Place West. The cause of such a large-scale earth movement is inferred to be due to progressive shoreline erosion by wave action. Construction of the Great Northern Railroad (presently owned by Burlington Northern) along the beach has halted the shoreline erosion process. No large-scale earth movements have been recorded for this area in modern times. However, subsequent to the ancient slide, the mass of soil within the body of the slide has experienced numerous small-scale adjustments. This type of post -slide adjustment is common and typically occurs in the form of shallow earth slumps until a more stable slope geometry is achieved. The study by Roger Lowe Associates has indicated that the stability of the Meadow dale area is highly sensitive to ground water levels. Improvements to local site drainage, including the installation of sewers and storm drains has had a positive impact on the stability of the area. W-5385-02 1 -iIR Ms. Ursula Schluter SNON 6WILSON, INC. January 26, 1994 Page 4 Review of available records and reports indicates that the Schluter property is located within an area of near -surface slide activity. The "Report of Geologic Evaluation, Meadowdale Area, Edmonds, Washington for the City of Edmonds," dated 1968, includes a description of a landslide which occurred in 1955-56. The Schluter property lies within the boundaries of this area. Also, according to the Great Northern/Burlington Northern Railroad records, three slides occurred along the section of track (MP 21.6) in the immediate vicinity of the Schluter property between 1949 and 1956. The railroad subsequently built retaining walls along the toe of the slope, including along the Schluter property. The records indicate that sliding occurred on properties south of the Schluter's in 1973-74, but there is no indication that sliding has occurred on the Schluter property since its wall was constructed. RECOMMENDATIONS ` In our opinion, the existing fill and slide debris which covers the site would not provide suitable support for the proposed structures. We understand that the house design presently calls for augercast piles with diameters of 24 inches. In our opinion, 24-inch-diameter augercast piles, with a minimum penetration of 12 feet into the hard silt would be capable of developing an allowable capacity of at least 25 tons each with an adequate factor of safety. This pile capacity could be increased by 1/3 for seismic loadings. We expect that settlement of properly installed piles or piers at this site would be negligible. We expect that the bearing stratum will be located at depths ranging from about 15 to 25 feet at the building site and piles should penetrate at least 12 feet into the hard, gray silty clay. Based on the results of the explorations, we estimate that foundation piles will extend about 40 feet below the existing ground surface. The depth to the bearing stratum for each pile should be determined by a geotechnical engineer or his representative during construction. In order to provide stiffness against potential soil creep, we recommend that the building foundations be tied together in the up -and -down -slope direction with a grade beam. This beam should have moment connections with the tops of the piles. The piles and grade beam will form a stiff structural system to resist soil movement in the downslope direction. In order to increase the stability of the site we recommend that at least one trench subdrain be installed across the site in roughly a north -south direction, at the approximate location W-5385-02 t 1 Ms. Ursula Schluter SANON 6WILSON, INC. January 26, 1994 Page 5 shown in Figure 1. Subdrains would consist of a 6-inch (minimum) diameter slotted plastic pipe bedded in 3/8-inch pea gravel in the bottom of a sand -filled trench. The location of the trench subdrain will depend on design of the house, and should be determined after the layout of the house has been established in the field. We recommend that no additional fill be placed on the site, as the additional weight could reduce the stability of the site. Much of the soil excavated from trench subdrains should be removed form the site, although some may be used as backfill in the upper 4 or 5 feet of the trench. We should review any plans for placement of fill on this site so that unstable conditions are not created. It is our opinion that the proposed structure, supported on augercast concrete piles, will not experience significant lateral deflections or settlement. With regard to utility connections, we do not foresee the need for flexible utility connections for the proposed structure. Site Stability The results of our studies indicate that the property can be developed and the proposed residence constructed in such a way as to increase the stability of the site. We expect that construction of a trench drain across the property will lower the ground water level and increase the stability of the site. In our opinion, once this site is developed in accordance with our recommendations, the probability of substantial loss due to future sliding will be less than 30 percent in a 25-year period. Excavation for the recommended trench subdrain will result in an increased possibility of local sliding in the immediate vicinity of the trench. This risk of sliding would be limited to within about 30 feet of the excavation and would not endanger the street or neighboring properties. The use of a trench box and immediately backfilling the completed trench to minimize the length of excavation open at any one time will minimize the potential for sliding during construction. Completed portions of the trench will immediately begin to drain the site, and the stability of the site should increase as the work proceeds. Concrete Piles Augercast piles are installed by rotating a continuous -flight hollow -stem auger to a pre- determined depth. When the depth is reached, a high strength sand -cement grout is pumped, W-5385-02 Ms . Ursula Schluter ANNON 6WILSON, INC. January 26, 1994 Page 6 under controlled pressure, through the center of the shaft as the auger.is slowly withdrawn. I By maintaining pressure in the grout line and slowly extracting the auger no faster than an equivalent volume of grout is pumped, a continuous column of concrete is formed. A single large reinforcing rod can be installed for the full pile length through the hollow -stem of the ' auger, and/or a reinforcing cage can be placed in the column of wet grout. The quality of augercast concrete piles is primarily dependent on the procedures and workmanship of the Contractor who installs them. A properly functioning pressure gage and pump stroke counter or flow meter should be provided on the grout pump to assist in monitoring augercast pile installation. The auger should be withdrawn with slow positive rotation at a slow steady pull and should not be pulled until the grout has been pumped a ' few feet above the tip. Lateral Earth Pressures and Retaining Structures Lateral forces from wind, seismic, and earth pressures or other loadings would be resisted by passive earth pressure against the buried portions of structures, and from lateral pile resistance. In our opinion, lateral earth pressures in the downslope direction could be estimated using an equivalent fluid weight of 35 pounds per cubic foot (pcf), plus one pound per cubic foot for each degree of upward inclination of the backslope above the wall. This pressure should be assumed to act over three times the diameter of the pile to a depth of 5 feet. This active lateral force will be resisted by passive pressure against the portion of the piles below a depth of 5 feet. An equivalent fluid weight of 280 pcf may be used to estimate the passive resistance against the down -slope sides of the piles and should be assumed to act over twice the pile diameter. This value may also be used to estimate passive resistance in the cross -slope directions. The lateral capacity of piles will depend on the size and stiffness of the pile. Battered piles can also be installed to carry lateral loads, if necessary. Below -grade walls and grade beams of the proposed structure should be designed for an g equivalent fluid pressure of 55 pounds per cubic foot (pcf), plus one pound per cubic foot for each degree of upward inclination of the backslope above the wall. Cantilevered retaining walls which are not connected to the house could be designed for an equivalent fluid pressure of 35 pcf, plus one pound per cubic foot for each degree of upward inclination of the backslope above the wall. These pressures assume the walls are drained so that W-5385-02 Ms. Ursula Schluter SHANNON 6WILSON, INC. January 26, 1994 Page 7 hydrostatic pressures cannot develop. Recommendations for wall drainage and back filling are presented on Figure 6. We recommend that a coefficient of friction of 0.5 be used between cast -in -place concrete and soil for nonpile-supported structures. Base friction should not be considered beneath pile supported portions of the structure. A trench box may be required for installation of the drainage trench. Lateral earth pressures for design of trench -box shoring are presented in the attached Figure 4. Drainage Because of the large amount of groundwater seepage at this site, development should include the installation of one or more trench subdrains to lower the groundwater level and improve the stability of the site. We expect that at least one trench subdrain will be required, extending roughly north -south across the property as shown on Figure 1. A typical trench subdrain installation is shown on Figure 5. The subdrains should consist of a 6-inch (minimum) diameter slotted plastic pipe surrounded by at least 8 inches of 3/8- inch pea -gravel at the bottom of a trench. The trench bacldill should consist of drainage sand and gravel, gradation specifications of which are presented on Figure 5. Native site soils do not meet the requirements for drainage sand and gravel. The trench subdrains should extend to a depth of 8 to 15 feet, or 1-foot below the contact between the fill/slide debris and the stiff to hard native soils. It should drain south to the property line and, if possible, should be connected with a tightline to the existing storm water drainage system which runs up and down the slope near the south property line. We expect that the trench excavation can be completed with open cut methods using stable side slopes; however, a trench -box shoring system should be used where appropriate. Installation of the subdrain trench should begin at the lower end and proceed up -slope. The pipe should be installed and the trench should be bacldilled with drainage materials as the excavation proceeds, so that not more than about 30 feet of trench is open at a time. This will reduce the potential for caving and local sliding during trench installation. It may be W-5385-02 • Ms. Ursula Schluter SHANNON 6WILSON. INC. 1, 'January 26, 1994 Page 8 necessary to periodically stop work for a day or two to let the site drain before advancing ' the trench. Footing drains consisting of 6-inch-diameter slotted plastic pipe should be installed on the tupslope side of any below -grade walls and grade beams. Freely draining sand or sand and gravel should be used as backfill. - Wall drainage and backfill recommendations are presented on Figure 6. The downspout water from the structure should be conveyed to a suitable discharge point, such as the existing storm drainage system, in a tightline. Subsurface drainage and downspout water should not flow onto the ground surface below the structure or onto the slope and should not flow into perforated footing drains. Erosion Control Erosion at the site during construction can be minimized by implementing the rec- ommendations in the Wet Weather Earthwork section, and can be controlled through the judicious use of fabric silt curtains and/or straw bales. The site should be seeded as soon as possible after grading, and vegetation should be encouraged. Wet Weather Earthwork The soils at the site are generally moisture sensitive, and will become soft and difficult to work when wet. Pile installation and other earthwork should not be accomplished during periods of heavy rainfall. If earthwork is to be accomplished in wet weather or under wet conditions when control of soil moisture content is not possible, fill should contain no more than 5 percent material passing the No. 200 mesh sieve, by weight, based on the minus 3/4 inch fraction. In addition: a) Earthwork should be accomplished in small sections and carried through to completion to minimize exposure to wet weather. If there is to be traffic over the exposed subgrade, the subgrade should be protected with a compacted layer of clean sand and gravel or crushed rock. The size or type of equipment may have to be limited to prevent soil disturbance; b) No soil should be left uncompacted so it can absorb water. Soils which become too wet for compaction should be removed and replaced with clean granular material; and, W-5385-02 Ms . Ursula Schluter SONNON &WILSON, INC. January 26, 1994 Page 9 c) Excavation and placement of fill should be observed on a full time basis by a person ' experienced in wet weather earthwork to determine that all unsuitable materials are removed and suitable compaction and site drainage is achieved. We recommend that these recommendations for wet weather earthwork be included in the contract specifications. Construction Monitoring and Plans Review We have worked with your architect and engineer in the design of foundations for the proposed structure and the necessary drainage installations at the site. We have also reviewed the portions of the plans which pertain to earthwork and foundations to determine f that they are consistent with our recommendations. We recommend that we be retained to monitor earthwork construction, including drainage and augercast pile installations, to determine that the work is accomplished in a suitable manner. Installation of the trench subdrain and foundation piles should be monitored on a full time basis. This monitoring should include verifying the depth of competent bearing soil and measurement of the volume of grout placed into each pile. / LIMITATIONS ! The conclusions and recommendations presented in this report are based on site conditions as they presently exist and assume the subsurface conditions are not significantly different tfrom those indicated in the explorations performed by Shannon & Wilson, Inc. or others. If during construction, subsurface conditions different from those encountered in the ' explorations and site reconnaissance are observed or appear to be present, we should be advised at once so that we can review those conditions and reconsider our recommendations where necessary. If there is a substantial lapse of time between submission of our report rand the start of work at the site, or if conditions have changed due to natural causes or construction operations at or near the site, it is recommended that this report be reviewed to determine the applicability of the conclusions and recommendations considering the changed conditions and time lapse. This report was prepared for the use of the Owner or Engineer/Architect in the design of the structure. It should be made available to prospective contractors and/or the Contractor for information on factual data only and not as a warranty of subsurface conditions. To assist you and others in understanding the use and limitations of our report, Shannon & Wilson, Inc. has prepared the attachment °Important Information About Your Geotechnical ' Engineering Report." W-5385-02 I- ..'. 1 0 Ms. Ursula Schluter SHANNON &WILSON, INC. ' - January 26, 1994 Page 10 iThe scope of our work did not include environmental assessments or evaluations regarding ' the presence or absence of wetlands or hazardous or toxic substances in the soil, surface water, groundwater on or below this site. Unanticipated conditions are commonly encountered and cannot be fully determined by f merely performing a site reconnaissance, taking soil samples or making explorations. Such unexpected conditions frequently require that additional expenditures be made to achieve a properly constructed project. Some contingency fund is recommended to accommodate such potential extra costs. We appreciate your continued confidence in our firm, please call if you have any questions. Sincerely, SHANNON & WILSON, INC. �`ONAL //Z 7/o y EXPIREs7/25// 4p5'' Ralph N. Boirum, P.E. Senior Associate RNB:TEK/mb Enclosures: Figure 1 - Site Plan Figure 2 - Subsurface Profile A -A' Figure 3 - Log of Boring B-1 Figure 4 - Lateral Earth Pressures Figure 5 - Typical Trench Subdrain Installation Figure 6 - Typical Foundation Subdrain And Backfill Figure 7 - Test Pit Logs Important Information About Your Geotechnical Engineering Report W5385-02XT4/W5385-1kd/1kd W-5385-02 0 '(-"-- y" - •-----7-----� -c— -TOE-=---_----- -• s �. � s •aa t ck �z `moo_ "J' 'A ��:. �• „ -----__�.Ah Id H.LSL a - 1,----%•------------y--------�--- J J I ��c �• .ice _ •V� Z. N #��\ • I 1 � nnia •aa_rv_a = N U J N d N O ;i e w Q a '2� r' co oz N ` ca old! lL O_ m G o. w E F� cL H- d .s t HI E Z 0 =° n C) 0E� E ,, t NZo co in N .� �] \ k uj ---- $ 0 9,U! UOIJeA913 OD to . \ C.- � �| ®k C, CL /� — --.--------------------- m/ zk m » \ m � � ~ C� kk ui 2 M $ a z■ . 2 k k kf ] ) � § � ) $ k O| U SOIL DESCRIPTIO ILL o LL �ndard Penetration Resistance s � n �' (140 lb. weight, 30" drop) CL o to ° 3 a A Blows per foot Surface Elevation: 98 Feet a) Cn rn 0 0 20 40 60 Loose, brown, silty, fine SAND; moist; wet @ 18 ft. mixed with clayey SILT with = • mottled disturbed appearance with = • possible slide plane @ 20 ft. (Fill and Slide Debris) SM. = 10 ............ ... _.._........ 20.9 = m 20_�....._....-- Stiff to very stiff, gray, fine sandy SILT to slightly clayey SILT; wet; with laminated = o • structure; ML. co = 0 30 • ...... 36.0 = • Hard, gray, silty CLAY; moist; laminated with fine sand partings and wet sand layer = 40 at 46.3 ft.; CL. _ • = 50 • 56.0 = • Very stiff, gray, silty CLAY; moist; with scattered iron stained sand layers and = 60 ..-- • disturbed blocky appearance; (Possible s1 5 ancient slide plane) CL. BOTTOM OF BORING COMPLETED ON 11 /19/93 70 80 90 LEGEND 0 20 40 60 • % Water Content Sample Not Recovered Surface Seal Plastic Limit I—• Liquid Limit = 2" O.D. Split Spoon Sample ® Annular Sealant Natural Water Content IL 3" O.D. Shelby Tube Sample Piezometer Screen ® Grout Ursula Schluter Q Water Level - 15620 75th Place West Edmonds, Washington NOTES 1. The stratification lines represent the approximate boundaries between LOG OF BORING B-1 soil types, and the transition may be gradual. 2. The discussion in the text of this report is necessary for a proper understanding of the nature of subsurface materials. January 1994 W-5385-02 3. Water level, if indicated above, is for the date specified and may vary. 4. Refer to KEY for explanation of 'Soil Log' symbols and definitions. SHANNON & WILSON, INC. FIG. 3 5. USC letter symbol based on visual classification. Geotechnical and Environmental consultants u 1 I Li u VER&OFT TO SOFT SILTS AbM CLAYS mqw 3 FT. MIN.—� }•— AVERAGE HEIGHT HA EXCAVATED MATERIAL STEEL TRENCH / BOX - MAKE EXCAVATION SLIGHTLY WIDER H THAN WIDTH OF BOX TO PERMIT / BOX TO BE PULLED THROUGH TRENCH I-�-- 50H psf 50HA psf (SURCHARGE DUE TO EXCAVATED MATERIAL) LATERAL EARTH PRESSURE FOR STEEL TRENCH BOX 3 F T. M I N. --• �-- AVERAGE H I HEIGHT A EXCAVATED MATERIAL 0.25 SHORING SYSTEM H TRENCH 50H psf 5OF^ psf (SURCHARGE DUE TO EXCAVATED MATERIAL) LATERAL EARTH PRESSURE FOR BRACED EXCAVATION NOTES 1. H AND HA ARE HEIGHTS IN FEET. 2. HYDROSTATIC PRESSURES SHOULD BE ADDED TO THE ABOVE VALUES WHERE APPLICABLE. 3. THE CONDITIONS OF BOTTOM HEAVE SHOULD BE STUDIED. 4. EXCAVATED SOIL SHOULD BE STOCKPILED AT LEAST 3 FEET FROM THE EXCAVATION, AND FURTHER AS INDICATED BY BOTTOM HEAVE STUDIES. i 1-Ft. On -site Soil Washed 3/8" Pea Gravel (8" min. above pipe, 12" on sides, 4" below) Existing Ground Surface Trench Excavation 6-in. Minimum Diameter Slotted Plastic Pipe Trench Bottom and Subdrain Pipe Sloped to Drain SPECIFICATIONS FOR DRAINAGE SAND AND GRAVEL Percent Passing Not to Scale Sieve Size by Weight 1-1/2 100 Ursula Schluter Residence 3/4 90 -100 Edmonds, Washington 1 /4 75 -100 No. 8 65 - 92 TYPICAL TRENCH SUBDRAIN No. 30 20 - 65 INSTALLATION No. 50 5 - 20 No. 100 0-2 January 1994 W-5385-02 (by wet sieving) (non -plastic) RHANNON & WILSON, INC. FIG. 5 r'sical and En*onmental Consdtants Pavement or 8" Impervious Soil Excavation Slope (Contractor's Responsibility) 8" Min. Cover of 3/8' Pea Gravel Over Pipe Sloped to Drain Away From Basement or Structure Retaining Wall Washed 3/8" Pea Gravel • ° • , or Clean Sand and Gravel � o 0 Granular Backfill oo ° (See Note 1) 18' , Damp Proofing . Min.. 0 0 °. os 0 o ° Weep Holes , ,' ° o 0 00 (See Note 1) Floor Slab o .o o .0 o •. Subdrain Pipe Not to Scale NOTES 1. Wall backfill should consist of freely draining granular soil with no more than 5% (by weight based on the minus 3/4-inch portion) passing the No. 200 sieve (by wet sieving), with no plastic fines. 2. Backfill behind the wall should be compacted with hand -operated equipment. Heavy equipment should not be used as such equipment operated near the wall could increase lateral earth pressures and possibly damage the wall. 3. Backfill should be placed in layers not exceeding 6' loose thickness, and should be densely compacted. Beneath paved areas, compact to at least 95% of the Modified Proctor maximum dry density ( ASTM: D1557-70), otherwise compact to 92% compaction. Washed Pea Gravel Vapor Barrier 6" Min. of 10MM n 1w1 nlnc 4" minimum diameter perforated or slotted plastic pipe; tight joints; sloped to drain (6'/100' min. slope). Provide clean -outs. TEST PIT LOGS Al 0' - Duff, topsoil, and roots 1.3' - Variable brown silty fine sand with gravel and clasks of silt -clay mixture (slide debris) (loose) 13.0' - Completed February 25, 1986; no groundwater encountered #2 0' - Duff, topsoil, and roots Variable sandy silt and silty sand (slide debris) ±13.5' - Sandy gravel, slight groundwater seepage throughout ±15.5' - Blue -gray silty clay (severely fissured and with slickensides) ±17.0' - Completed February 25, 1986 fi3 0' - Variable silt -sand -gravel mixture (saturated) (slide debris) 3.0' - Blue -gray silty clay (med stiff) (old slide debris) 8.1' - Tan silt (hard) 14.5' - Completed February 25, 1986; groundwater flow from upper 3 feet #4 0' - Highly variable silt -sand -clay mixture (slide debris) 7.0' - Blue -gray silty clay (fissured, ancient slide debris) 11.0' - Tan silt (hard) 13.0' - Blue -gray silt (hard) 16.0' - Completed February 25, 1986; seepage from 4-7 feet FIG. 7 • W-5385-01 SHANNON & WILSON, INC. - Geotechnical Consultants - Engineering and Applied Geosciences Over 35 Yea rs of Excellence fce 400 North 34th Street, Suite 100 • P.O. Box C-30313 • Seattle, WA 98103 • (206) 632-8020 • Fax: (206) 547-0386 March 29, 1990 Ms. Ursula Schluter 21701 80th Avenue West #4 Edmonds, Washington 98020 GEOTECHNICAL REPORT, PROPOSED RESIDENCE AT LOTS 1 & 2, 75TH PLACE WEST, EDMONDS, WASHINGTON This report presents the results of our geotechnical reconnaissance and evaluation for your pro- posed residence on 75th Place West in Edmonds. The purpose of our work was to evaluate the site and provide recommendations to aid in foundation design for the proposed single-family resi- dence. Our work included a visit to the site to perform a reconnaissance and a review of existing subsurface information about the site contained in a geotechnical report by Earth Sciences, dated March 21, 1986. SITE AND PROJECT DESCRIPTION The property is located on the west side of 75th Place West in the Meadowdale area of Edmonds, Washington. The property measures approximately 97 feet by 190 feet and consists of two lots located about 200 feet north of the intersection of 75th Place West and 158th Street S.W. The legal description for the property is: lots 1 & 2, Block 28, Meadowdale Beach, Snohomish County, Washington. The lots are bordered on the east by 75th Place West and on the west by the Burlington Northern Railroad right-of-way. The property is shown on the Site Plan, Figure 1. An occupied lot lies to the south of the subject property and a lot with an abandoned house and shed lies to the north. Portions of the abandoned structures which he on the lot to the north protrude into the subject property. The ground surface is covered with dense brush and blackberry vines. The site slopes moderately downward from 75th Place West to the BNRR tracks. The average slope is about 1 vertical to 3 horizontal (IV to 3H). A retaining wall about 4 feet high has been Seattle • Everett • Fairbanks • Anchorage • St. Louis PRESIDENT: Earl A. Sibley, P.E. SR. VICE PRESIDENT: Atef A. Azzam; Raymond P. Miller, P.E.; Harvey W. Parker, P.E.; George Yamane, P.E. VICE PRESIDENT: Herman H. (Tex) Druebert, P.E.: Richard H. Gates, P.E.; W. Paul Grant, P.E.; Leland B. Jones, P.E.; Thomas E. Kirkland, P.E.; Gerry Millar, R.G.,; Frank W. Pita, P.E., P.G.; Ming -Jinn (Jim) Wu, P.E. CONSULTANT: William L. Shannon, P.E. Ms. Ursula Schluter • March 29, 1990 Page 2 W-5385-01 built by the railroad along the toe of the slope. We understand this wall was constructed to prevent debris from sliding onto the railroad right-of-way. We understand that the proposed residence will be a multi -story, single-family house. We expect that a garage for off-street parking will also be constructed. The dimensions and locations for these structures are not known at this time. SUBSURFACE CONDITIONS The results of the explorations presented in the report by Earth Sciences dated March 21, 1986, indicate that the site is generally underlain by 8 to 17 feet of slide debris consisting of loose sand, silt, and silty clay. Below the slide debris the soils consist of hard tan to blue -gray silt. The hard silt appears to be glacially consolidated. Considerable groundwater seepage was observed at the site during our reconnaissance. Groundwater flow was also noted on the test pit logs in the report by Earth Sciences. According to the report by Earth Sciences and a "Landslide Hazards Map" by Roger Lowe Associates, Inc., dated October 16, 1979, the property has been subjected to slope instability and sliding in the form of slumps of surface soils loosened by previous sliding. CONCLUSIONS AND RECOMMENDATIONS In our opinion, the existing fill and slide debris which covers the site would not provide suitable support for the proposed structures. We therefore recommend that the proposed structure be sup- ported on augercast concrete piles or drilled piers bearing in the hard silt which underlies the site. Augercast methods are preferred at this site because of the potential for caving in the loose soils. We expect that the bearing stratum will be located at depths ranging from about 8 to 17 feet and piles should penetrate at least 12 feet into the hard soil. The depth to bearing stratum for each pile should be determined during construction. SHANNON & WILSON, INC. Ms. Ursula Schluter • W-5385-01 March 29, 1990 Page 3 For augercast piles or drilled piers we recommend a minimum diameter of 16-inches. In our opinion, 16-inch diameter augercast piles or drilled piers, with a minimum penetration of 12 feet into the hard silt would be capable of developing an allowable capacity of 20 tons each with an adequate factor of safety. We expect that settlement of properly installed piles or piers at this site would be negligible. In order to provide stiffness against potential soil creep, we recommend that the building founda- tions be tied together in the up -and -down -slope direction with a reinforced concrete grade beam. This beam should have moment connections with the tops of the piles. The piles and grade beam will form a stiff structural system to resist soil movement in the downslope direction. In order to increase the stability of the site we recommend that one or more trench subdrains be installed across the site in roughly a north -south direction. Subdrains would consist of slotted plastic pipe bedded in 3/8-inch pea gravel in the bottom of a sand -filled trench. The location of the trench subdrains will depend on design of the house, and should be determined after the layout of the house and floor grades have been established. We recommend that no additional fill be placed on the site, as the additional weight could reduce the stability of the site. Most of the soils excavated from trench subdrains or basement areas should be removed form the site. We should review any plans for placement of fill on this site so that unstable conditions are not created. Concrete Piles Augercast piles are installed by rotating a continuous -flight hollow -stem auger to a pre -determined depth. When the depth is reached, a high strength sand -cement grout is pumped, under controlled pressure, through the center of the shaft as the auger is slowly withdrawn. By maintaining pres- sure in the grout line and slowly extracting the auger no faster than an equivalent volume of grout is pumped, a continuous column of concrete is formed. A single large reinforcing rod can be installed for the full pile length through the hollow -stem of the auger, and/or a reinforcing cage can be placed in the column of wet grout. SHANNON & WILSON. INC. Ms. Ursula Schluter • March 29, 1990 Page 4 W-5385-01 The quality of auger -cast concrete piles is primarily dependent on the procedures and workmanship of the Contractor who installs them. A properly functioning pressure gage and pump stroke counter should be provided on the grout pump to assist in monitoring auger -cast pile installation. The counter is used to determine the approximate volume of grout pumped by counting the number of strokes of a displacement -type pump. The pump should, therefore, be calibrated prior to its use. The pressure gage is used to monitor the pressure of the grout to evaluate the rate at which the auger should be retracted, and if the auger or hoses are plugged. The auger should be withdrawn with slow positive rotation at a slow steady pull and should not be pulled until the grout has been pumped a few feet above the tip. Piers are constructed by drilling a hole with a short, single -flight auger. The auger is connected to a kelly bar which is rotated and lowered in and out of the borehole with a truck- or track -mounted drilling rig. When the hole has been advanced to the required penetration, all loose and disturbed soil at the bottom should be removed with a clean -out bucket which has the same diameter as the drilled borehole. Based on information from the exploratory test pits, it is our opinion that groundwater could be a problem during drilled pier installation at this site. Should caving occur in the loose silts and sands that are present at the site, casing would be needed in the upper portion as appropriate. After the pier has been cleaned and dewatered, reinforcing and concrete are placed in the hole. Reinforcing cages should have hole -centering guides. The concrete should have a . slump of at least 6 inches and be placed in the borehole through a funnel or 'elephant trunk' in order to prevent the free -falling concrete from hitting the borehole walls and contaminat- ing the concrete. Lateral Earth Pressures and Retaining Structures Basement level walls of the proposed structure should be designed for an equivalent fluid pressure of 55 pounds per cubic foot (pcf), plus one pound per cubic foot for each degree of upward incli- nation of the backslope above the wall. Cantilevered retaining walls which are not connected to the SHANNON & WILSON, INC. Ms. Ursula Schluter March 29, 1990 Page 5 W-5385-01 house could be designed for an equivalent fluid pressure of 35 pcf, plus one pound per cubic foot for each degree of upward inclination of the backslope above the wall. These pressures assume the walls are drained so that hydrostatic pressures cannot develop. Recommendations for wall drainage and backfilling are presented on Figure 3. Lateral forces would be resisted by passive earth pressure against the buried portions of structures and by friction against the bottom. In our opinion, passive earth pressures in backfill could be estimated using an equivalent fluid pressure of 280 pounds per cubic foot (pcf) above the ground- water table and 140 pcf below the water table. These values assume that the structures extend at least 18 inches below the lowest adjacent grade, and the backfill around (below) the structure is a horizontally graded, compacted granular fill. We recommend that a coefficient of friction of 0.5 be used between cast -in -place concrete and soil for non -pile supported structures. Base friction should not be considered beneath pile supported portions of the structure. Drainage Because of the large amount of groundwater seepage at this site, development should include the installation of trench subdrains to lower the groundwater level and improve the stability of the site. We expect that one or more trench subdrains will be required, extending approxi- mately north -south across the property near the east property line and again at about the mid point of the property. Depending on the layout of the structure, the footing drains along a day- light basement may function as one or more of the required subdrains. The locations and depths of the subdrains should be evaluated once the locations of the structures are known. A typical trench subdrain installation is shown on Figure 2, and a footing subdrain is shown on Figure 3. The subdrains should consist of slotted plastic pipe surrounded by at least 8 inches of drainage sand and gravel at the bottom of a trench filled with drainage sand and gravel, gradation specifications are presented on Figure 2. Native site soils do not meet the requirements for drainage sand and gravel. SHANNON & WILSON, INC. Ms. Ursula Schluter • March 29, 1990 Page 6 W-5385-01 The trench subdrains should extend at least 5 feet below the existing ground surface and at least to the elevation of any proposed excavation level. It should drain south to the property line and, if possible, should be connected with a tightline to the existing storm water drainage sys- tem which runs up and down the slope near the south property line. Caving of the sides of the trench is likely during installation of the trench subdrain. Installation should begin at the south end and proceed up -slope. It may be necessary to periodically stop work for a day or two to let the site drain before advancing the trench. Footing drains consisting of 4-inch (minimum) diameter slotted plastic pipe should be installed on the upslope side of all retaining or basement walls. Freely draining sand or sand and gravel should be used as backfill adjacent to walls. Wall drainage and backfill recommendations are presented on Figure 3. The downspout water from the structure should be conveyed to a suitable discharge point, such as the existing storm drainage system, in a tightline. Subsurface drainage and downspout water should not flow onto the ground surface and should not flow into perforated footing drains. The soils at the site are generally moisture sensitive, and will become soft and difficult to work when wet. It would be most advisable to schedule earthwork during the dry weather months. Pile or pier installation and any other earthwork should not be accomplished during periods of heavy rainfall. If fill is to be placed in wet weather or under wet conditions when control of soil moisture content is not possible, the fill should contain no more than 5 percent material passing the No. 200 mesh sieve, by weight, based on the minus 3/4 inch fraction. In addition: a.) Earthwork should be accomplished in small sections and carried through to completion to minimize exposure to wet weather. If there is to be traffic over the exposed subgrade, the sub - grade should be protected with a compacted layer of clean sand and gravel or crushed rock. SHANNON & WILSON, INC. Ms. Ursula Schluter • March 29, 1990 Page 7 W-5385-01 b.) No soil should be left uncompacted so it can absorb water. Soils which become too wet for compaction should be removed and replaced with clean granular material; and, c.) Excavation and placement of fill should be observed on a full time basis by a person expe- rienced in wet weather earthwork to determine that all unsuitable materials are removed and suitable compaction and site drainage is achieved. We recommend that these recommendations for wet weather earthwork be included in the con- tract specifications. Construction Monitoring and Plans Review We recommend that we be retained to work with your architect to design the necessary drainage installations at the site and to review the portions of the plans and specifications which pertain to earthwork and foundations to determine if they are consistent with our recommendations. We also recommend that we be retained to monitor earthwork construction, including drainage and drilled pier or augercast pile installations, to determine that the work is accomplished in a suitable manner. The installation of concrete piles or drilled piers should be monitored on a full time basis. This monitoring should include verifying the depth of competent bearing soil and measurement of the volume of grout placed into each pile. LIMITATIONS The conclusions and recommendations presented in this report are based on site conditions as they presently exist and the subsurface conditions are not significantly different from those indicated in the test pit explorations performed by Earth Sciences or inferred from our site reconnaissance. If during construction, subsurface conditions different from those encountered in the explorations and site reconnaissance are observed or appear to be present, we should be advised at once so that we can review those conditions and reconsider our recommendations where necessary. If there is a substantial lapse of time between submission of our report and the start of work at the site, or if SHANNON & WILSON. INC. ' Ms. Ursula Schluter* • March 29, 1990 Page 8 W-5385-01 conditions have changed due to natural causes or construction operations at or near the site, it is recommended that this report be reviewed to determine the applicability of the conclusions and rec- ommendations considering the changed conditions and time lapse. This report was prepared for the use of the Owner or Engineer/Architect in the design of the struc- ture. No soil boring or test pit explorations have been accomplished for this study. Unanticipated conditions are commonly encountered and cannot be fully determined by merely per- forming a site reconnaissance, taking soil samples or making explorations. Such unexpected conditions frequently require that additional expenditures be made to achieve a properly constructed project. Some contingency fund is recommended to accommodate such potential extra costs. We appreciate your continued confidence in our firm, please call if you have any questions. Sincerely, SHANNON & WILSON, INC. .80 �0F W.G i /f • I I . , Ralph N. Bd1%4 Senior Associate Enclosures: Figures 1 - 3 . SHANNON & WILSON. INC. MUNAg- 30---'�'— a O o� E a pl92 Zw C Cry Yid a0) aro, E Ed N d U ro�ro CD N r2 Approx 1 ft. On -site Soil Trench Excavation Drainage Sand and Gravel Washed 3/8" Pea Gravel (8" minimum above pipe, 12" on sides, 4" below) 6" Minimum Diameter Slotted Plastic Pipe Trench Bottom and Subdrain Pipe Sloped to Drain Specification for Drainage Sand and Gravel a 1-1/2 100 3/4 90 to 100 1 /4 75 to 100 No. 8 65 to 92 No. 30 20 to 65 No. 50 5 to 20 No. 100 0 to 2 By Wet Sieving Not to Scale Slope To Drain Away From Structure Pavement or 8" Impervious Soil Clean granular backfill, (See note 1) Excavation Slope (Contractor's responsibility) 8" Minimum cover of 3/8" gravel over pipe Subdrain Pipe Subdrain Pipe 4" Minimum diameter peforated or slotted plastic pipe; tight joints; sloped to drain (6"/100' Min.); Provide cleanouts. Basement or Retaining Wall Damp Proofing Washed 3/8" Pea Gravel or clean sand and gravel Vapor Barrier Weep Hales Floor Slab Pea Gravel `. 6" Min. 1. Wall backfill should consist of freely draining granular soil with no more than 511/6 (by weight based on the minus 3/4-inch portion) passing the No. 200 sieve( by wet sieving), with no plastic fines. 2. Backfill behind the wall should be compacted with hand - operated equipment. Heavy equipment should not be used as such equipment operated near the wall could increase lateral earth pressures and possibly damage he wall. 3. Backf ill should be placed in layers not exceeding 6" loose thickness, and should be densely compacted. Beneath paved areas, compact to at least 95% of the Modified Proctor maximum dry density ( ASTM: D1557-70,). Otherwise compact to 92 % compaction. Ursula Schluter Residence Edmonds, Washington TYPICAL FOUNDATION SUBDRAIN AND BACKFILL March 1990 W-5385-01 SHANNON & WILSON, INC. I FIGURE 3 Geotechnical Consultant BOX 126 HOBART, WASHINGTON TEL: AREA 206 - 682-6942 ERRTH SCIENCES EATO(. 98025 March 21, 1986 Mr. R. Michael Lantz, Jr. Maas & Lantz, P.S. Post Office Box 366 Kenmore, Washington 98028 Mr. E. H. Hodge 2963 Clearview Drive Anderson, California 96007 Re: Soil Conditions, Edmonds, Washington Gentlemen: Your contiguous residential properties in the Meadowdale area of Edmonds have been affected by landsliding, the most recent known episode of which was 30 years ago. The several block neighborhood is reported as an environmentally sensitive area in public records. You hope to construct single family homes on the parcels and recognize the need to explore and test subsurface conditions prior to construction and realize that conventional foundations and construction procedures may not be adequate. Too, the Building Department has investigative guidelines of which I was unaware until a few days ago. About two years ago, Mr. Lantz contacted me about investigating conditions for his lot; I outlined a scope of effort which I believed would be appropriate in the absence of specific plans and I estimated the fee for such. There were no further developments on the proposal until early this year. On behalf of both owners, Mr. Lantz gave authorization to proceed on February 11. Fieldwork was accomplished on February 25. This report describes the investigative procedure, summarizes observations and test results, tries to explain the relative risks, and offers general recommendations for development of the properties. Mr. Lantz has provided me with copies of a 16 October 1979 Report on Landslide Hazards Investigation, Meadowdale Area, Edmonds—,--Wa--sh ington for the City of tdmonds, by Roger Lowe Associates, Inc., and a 6 June 1985 Site Geotechnical Study for Mr. Harrison Jewell by Geological Services, —Inc., The Roger Lowe report covers an area including both the Lantz and Hodge properties and the Geological Services, Inc., study applies to the property Mr. R. Michael Lantz, Jr. Mr. E. H. Hodge Page Two March 21, 1986 immediately to the south of the Lantz property. The two outside reports were especially useful in understanding how your lots relate to neighborhood conditions, and the Lowe report provides a thorough analysis of hydrologic conditions and their relationship to slope stability. City personnel provided me with a revised slope stability map, an updated report by GeoEngineers, Inc., and a copy of the permit checklist. Introduction Page 8 of this report was prepared from a partial and untitled map provided by Mr. Lantz and from verbally related dimensions from him. It shows the size and configurations of the two parcels and their relationship to 75th Place West, the Burlington Northern Railway line, a vacated street running alongside the railroad, and to the Jewell property. As part of this investigation, two downhill profiles to illustrate terrain conditions at approximate scale across the subject sites. The profiles were constructed using a tape measure and hand-held inclinometer and are not to sufficient accuracy to be used for scaling dimensions. The profiles are shown on pages 9 and 10. In the absence of specific building plans and known building locations, I cannot offer specific recommendations which in themselves would be wholely adequate through design and construction phases without further comment, review, and inspection on my part. Understanding this report and complying with its recommendations will not eliminate all risks of slope instability or other problems stemming from or involving subgrade conditions. Theoretical attempts to quantitatively define slope risk in terms of critical angle, critical height, factor of safety, time duration until the next probable slide event, or probability of sliding in a given year are far less than precise in cases where conditions are as complex as they are on your properties. Much of the complexity is in the form of heterogeneity of strength, composition, structure, and groundwater caused by previous sliding; others result from climatic irregularities and the multiplicity of ages and types of "original" soil. It is the objective of this report to identify soils or conditions which are especially hazardous and ought to be mitigated or avoided in the course of development, in the process of identifying restrictive conditions, ground areas or strata of relatively greater stability will be found; hopefully, these will be used to the best advantage. Mr. R. Michael Lantz, Jr. Mr. E. H. Hodge Page Three March 21, 1986 Geologic Background An excellent description and historical account of subsurface conditions, soil origins, and past slide activity is found in the Roger Lowe Associates, Inc., report; I refer to that document for anyone interested in a fairly technical perspective. In brief, the landmass, which ,includes the Meadowdale area, originally consisted of horizontally layered formations of clay, sand, and various mixed gradations of soil, all of glacial or interglacial origin. Coastal erosion caused the development of ever -heightening and ever -steepening bluffs along the beach. Continued undercutting and oversteepening resulted in landsliding, the first instance of which was probably several thousand years ago. One effect of initial sliding was to create a new and higher steep face and thereby "set up" conditions for a systematic series of subsequent events. With continued coastal erosion, movement was not allowed to go to completion and permanent stability. Construction of the railroad halted the coastal erosion process, provided a vertical ballast on the slide toe, and provided some degree of horizontal retention. The stabilizing effect of the railroad would require centuries to bring significant improvement across the entire 40 odd acre slide mass. Improvement of stability in the strip immediately east of the railroad has been more rapid. With construction of homes and on -site sewage systems and with the installation of a community water system, there was a resultant net increase in groundwater recharge and with that, a decrease in stability of the area as a whole. The Lowe report refers to approximately 20 identifiable slides within the larger slide area since 1946. Within the past two years, storm and sanitary sewers have been installed which, together with drainage improvements on individual lots, have restored stability to its probable highest level in modern times. Even at its improved state, some future sliding is to be expected and, as best it can be quantified, the measure of stability of disturbed or displaced soils is below what most engineers, geologists, and informed owners would consider acceptable by Puget Sound standards. By the same standards, the yet undisplaced and undisturbed soils would generally be viewed as acceptable. Subsurface Conditions Soils were explored at four locations on the combined properties by digging test pits with a Case 580 Extendahoe. The services of a dozer and a winch truck were used to assist in maneuvering the hoe across the soft groundsurface. Test locations are shown on page 8. Log summaries of conditions at each location are presented on page 11. Mr. R. Michael Lantz, Jr. Mr. E. H. Hodge Page Four March 21, 1986 Both slide debris and undisturbed soils were exposed by test digging. Several distinctly different types of slide debris were noted. At each location, the uppermost slide debris contained a fraction of sand and was severely prone to sloughing. At Locations One and Two, the rate of sloughage was so great that it was not possible to explore deeper than shown on the logs. At Location Number One, the backhoe operator reported harder digging at and beyond the 13-foot depth, but identifiable strata could not be uncovered. At Locations Two, Three, and Four the sandy slide debris is directly or indirectly underlain by firmer clayey slide debris. The clayey debris was gray in color at the three locations and, to the untrained eye, is similar in appearance to undisturbed soil. Pits Three and Four terminated in a formation of silt hardpan. As is characteristic of low -permeability glacial deposits, they are brown in color near the surface and gray at depth. Hole Number Three terminated in the brown and Number Four in the gray; at the termination depth, the practical limit of reach of exploration was reached because of the extreme hardness of the silt. Shallow groundwater was observed in three of the four test holes. It is impossible to tell how the observed hydrologic conditions compare with conditions before the public drainage improvements were installed. Laboratory Tests Three-inch diameter thinwall samples were hydraulically pressed from the lower, clayey slide debris at Locations Three and Four. The samples were extruded, tested for moisture and unit weight and tested for unconfined compressive strength by the slow method. Test results are summarized on page 12. Casual review of those results makes it appear that the Number Three sample has superior strength to Number Four. The difference is attributed to differences in rates of applied strain. Neither sample displayed a definable yield point or failure point. The shapes of the stress -strain curves are interpreted to mean that even the oldest slide debris found beneath your properties is subject to extreme gradual deformation under modest loads. Conclusions I advise against the construction of any major improvements, the stability of which would be dependent on any of the materials described by this report as "slide debris". I believe that it would be within generally accepted standards of risk to construct improvements which depended only on the silt hardpan or deeper soils. It would not be possible to develop M • U O V U) X O cr CL a ► ► ► Id ---- a f- It a H 0 LANTZ a HODGE PROPERTIES A " BI B.N.RR. R/W VACATED STREET 4� 3 JEWELL LANTZ HODGE ' RESIDENCE PROPERTY PROPS RTY APPR OX. 20 TO 158th. STREET SW. E i 2 DENOTES _ TEST PIT 0 SCALE IN FEET 0 10 20 30 40 50 100 150 0 NORTH 5yr-79/? S-j�t,5' �Exi'Rr3sTl as ��t '�jOiOi`i) 0 N u! Ao � eo :I,- ',�- V I .r t • 0 Mr. R. Michael Lantz, Jr. Mr. E. H. Hodge Page Five March 21, 1986 adequate lateral strength on ordinary wood or concrete piles to allow that type of construction on the upper (eastern) halves of the two subject lots. By ordinary construction standards, neither would it be feasible to excavate ordinary footing foundations to safe soil on the upper halves of the lots. As a practical matter, developing the two lots in such a way as to depend only on undisturbed earth means constructing homes on the lower elevations. Even there, deeper than normal excavation will be required. I have the highest professional regard for those who prepared the Lowe report and agree with the methods they employed. Consistent with these views, I take no issue with mapped risk assessment figures. To fully understand how the Lowe report applies to your properties, you must understand that the assigned risks apply to surface soils in their present conditions; in areas coded "Hazard 411, and where debris is thin, the feasibility of safe development would be greater than Hazard 4-areas of thick debris. By the Lowe system, your properties are 4-A-90 30. If you and the City are agreeable to accepting the 30 percent risk for surface soil, you need not feel bound to follow my suggestions about constructing at lower elevations and founding all structures on undisturbed soil. In such a case, you could inadvertently increase the risk to more than 30 percent by careless construction practices. By adhering to established good practices for steep or marginally stable slopes, you should have little trouble keeping post -construction risk at 30 or less. Recommendations Assuming that you decide to hold risks to levels well below the 30 percent by depending only on the silt hardpan for foundation support, either of two general construction approaches should be followed. The Alternatives are shown schematically on the following page. In either case, clean, select, imported aggregate would be needed around and above all subgrade drains and all imported aggregates need be shrouded in filtering geofabric. Permanent drains must be installed to insure that water does not become ponded or trapped by the excavation or by constructed improvements. Method "A" would support major improvements on a structural fill of crushed quarry rock or quarry spalls. Method "B" would leave some or most of the slide debris beneath the building area but would have all foundations on undisturbed soil. "B" should be structurally engineered. In neither case should grading be done in such a way as to increase the net load on any of the non -bearing surfaces. Mr. R. Michael Lantz, Jr. Mr. E. H. Hodge Page Six March 21, 1986 I mooeZ t1' Z• , �e-7WL' O Mr. R. Michael Lantz, Jr. Mr. E. H. Hodge Page Seven March 21, 1986 Whichever method is adopted, I recommend that you coordinate with me throughout the design and construction phases, review grading, drainage, and foundation plans, and inspect the excavation in progress. For preliminary design purposes, I recommend that spread footings be designed to bear on either the silt hardpan or crushed rock at not more than 3 ksf. Retaining walls through slide debris would be designed to 45 pcf fluid pressures subject to the following: (1) backwall drains are provided; (2) select aggregate backfill is used fill height and laterally back a distance of h/3; (3) the wall is yieldable; for rigid cases, the earth pressure should be assumed to increase by one-third; (4) no backslope angle exceeds 20° and there is no surcharge; (5) unretained slide debris should not be depended upon for passive restraint. Limitations and Use This report was prepared for the exclusive use of the addressees for their use in planning and designing their own homes. It is not to be used by anyone outside the design team for the two said residences; it is specifically not for interested buyers, future owners, lenders, or real estate agents. The conclusions and recommendations expressed by this report were developed from random sampling, observations and from information provided by yourselves and others. To whatever degree the total of information now available to the undersigned, within the fee and scope agreed, might not be true or accurately representative of actual conditions, the conclusions and recommendations would be affected accordingly. The only express or implied warranty carried by this report is that the professional efforts were applied conscientiously, in good faith, and to recognized standards of good practice as defined and understood by the engineering community in this area at this time. The undersigned assumes no responsibility for design or construction which is not in compliance or which is of uncertain compliance with recommendations herein. Yours very truly, EARTH SCIENCES N. 2 p tt t each addressee JN � 11917 'Q �S 7 E Ei OVAL • TEST PIT LOGS #1 0' - Duff, topsoil, and roots 1.3' - Variable brown silty fine sand with gravel and clasks of silt -clay mixture (slide debris) (loose) 13.0' - Completed February 25, 1986; no groundwater encountered #2 0' - Duff, topsoil, and roots 1.1' - Variable sandy silt and silty sand (slide debris) ±13.5' - Sandy gravel, slight groundwater seepage throughout ±15.5' - Blue -gray silty clay (severely fissured and with slickensides) ±17.0' - Completed February 25, 1986 #3 0' - Variable silt -sand -gravel mixture (saturated) (slide debris) 3.0' - Blue -gray silty clay (med stiff) (old slide debris) 8.1' - Tan silt (hard) 14.5' - Completed February 25, 1986; groundwater flow from upper 3 feet #4 o' - Highly variable silt -sand -clay mixture (slide debris) 7.0' - Blue -gray silty clay (fissured, ancient slide debris) 11.0' - Tan silt (hard) 13.0' - Blue -gray silt (hard) 16.0' - Completed February 25, 1986; seepage from 4-7 feet S11,NLZY lL,oi;v�! . 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YL ��i-� I � • LQ v I g9 ZY I SON 1y3a�i - i ♦ "' . .a_. 4 Apt ;I i } W-5385-01 i SHANNON & WILSON, INC. 01,er 135 Yen rs Geotechnical Consultants Of — Engineering and Applied Geosciences -_ _ _ _ _— Excellcncc 400 North 34th Street, Suite 100 • P.O. Box C-30313 • Seattle, WA 98103 • (206) 632-8020 • Fax: (206) 547-0386 March 29, 1990 . 0 � —7, I Ms. Ursula Schluter 21701 80th Avenue West #4 Edmonds, Washington 98020 _:Ei 1 - , Fr-- � GEOTECHNICAL REPORT, PROPOSED RESIDENCE AT LOTS 1 & 2, 75TH PLACE WEST, EDMONDS, WASHINGTON This report presents the results of our geotechnical reconnaissance and evaluation for your pro- posed residence on 75th Place West in Edmonds. The purpose of our work was to evaluate the site and provide recommendations to aid in foundation design for the proposed single-family resi- dence. Our work included a visit to the site to perform a reconnaissance and a review of existing subsurface information about the site contained in a geotechnical report by Earth Sciences, dated March 21, 1986. The property is located on the west side of 75th Place West in the Meadowdale area of Edmonds, Washington. The property measures approximately 97 feet by 190 feet and consists of two lots located about 200 feet north of the intersection of 75th Place West and 158th Street S.W. The legal description for the property is: lots 1 & 2, Block 28, Meadowdale Beach, Snohomish County, Washington. The lots are bordered on the east by 75th Place West and on the west by the Burlington Northern Railroad right-of-way. The property is shown on the Site Plan, Figure 1. An occupied lot lies to the south of the subject property and a lot with an abandoned house and shed lies to the north. Portions of the abandoned structures which lie on the lot to the north protrude into the subject property. The ground surface is covered with dense brush and blackberry vines. The site slopes moderately downward from 75th Place West to the BNRR tracks. The average slope is about 1 vertical to 3 horizontal (IV to 311). A retaining wall about 4 feet high has been Seattle • Everett • Fairbanks • Anchorage • St. Louis PRESIDENT: Earl A. Sibley, P.E. SR. VICE PRESIDENT: Atet A. Auam; Raymond P. Miller, P.E.; Harvey W. Parker, P.E.; George Yamane, P.E. VICE PRESIDENT: Herman H. (Tex) Druebert, P.E.: Richard H. Gates. P.E.; W. Paul Grant, P.E.; Leland B. Jones. P.E.: Thomas E. Kirkland, P.E.; Gerry Millar, R.G.,; Frank W. Pita, P.E., P.G.; Ming•Jiun (Jim) Wu. P.E. CONSULTANT: William L. Shannon, P.E. Ms. Ursula Schluter W-5385-01 March 29, 1990 Page 2 built by the railroad along the toe of the slope. We understand this wall was constructed to prevent debris from sliding onto the railroad right-of-way. We understand that the proposed residence will be a multi -story, single-family house. We expect that a garage for off-street parking will also be constructed. The dimensions and locations for these structures are not known at this time. SUBSURFACE CONDPT ONS The results of the explorations presented in the report by Earth Sciences dated March 21, 1986, indicate that the site is generally underlain by 8 to 17 feet of slide debris consisting of loose sand, ' silt, and silty clay. Below the slide debris the soils consist of hard tan to blue -gray silt. The hard silt appears to be glacially consolidated. Considerable groundwater seepage was observed at the site during our reconnaissance. Groundwater flow was also noted on the test pit logs in the report by Earth Sciences. ' According to the report by Earth Sciences and a "Landslide Hazards Map" by Roger Lowe Associates, Inc., dated October 16, 1979, the property has been subjected to slope instability and sliding in the form of slumps of surface soils loosened by previous sliding. In our opinion, the existing fill and slide debris which covers the site would not provide suitable support for the proposed structures. We therefore recommend that the proposed structure be sup- ported on augercast concrete piles or drilled piers bearing in the hard silt which underlies the site. Augercast methods are preferred at this site because of the potential for caving in the loose soils. We expect that the bearing stratum will be located at depths ranging from about 8 to 17 feet and ' piles should penetrate at least 12 feet into the hard soil. The depth to bearing stratum for each pile should be determined during construction. ISHANNON & WILSON, INC. Ms. Ursula Schluter March 29, 1990 Page 3 W-5385-01 For augercast piles or drilled piers we recommend a minimum diameter of 16-inches. In our opinion, 16-inch diameter augercast piles or drilled piers, with a minimum penetration of 12 feet into the hard silt would be capable of developing an allowable capacity of 20 tons each with an adequate factor of safety. We expect that settlement of properly installed piles or piers at this site would be negligible. In order to provide stiffness against potential soil creep, we recommend that the building founda- tions be tied together in the up -and -down -slope direction with a reinforced concrete grade beam. This beam should have moment connections with the tops of the piles. The piles and grade beam will form a stiff structural system to resist soil movement in the downslope direction. In order to increase the stability of the site we recommend that one or more trench subdrains be installed across the site in roughly a north -south direction. Subdrains would consist of slotted plastic pipe bedded in 3/8-inch pea gravel in the bottom of a sand -filled trench. The location of the trench subdrains will depend on design of the house, and should be determined after the layout of the house and floor grades have been established. We recommend that no additional fill be placed on the site, as the additional weight could reduce the stability of the site. Most of the soils excavated from trench subdrains or basement areas should be removed form the site. We should review any plans for placement of fill on this site so that unstable conditions are not created. Concrete Piles Augercast piles are installed by rotating a continuous -flight hollow -stem auger to a pre -determined depth. When the depth is reached, a high strength sand -cement grout is pumped, under controlled pressure, through the center of the shaft as the auger is slowly withdrawn. By maintaining pres- sure in the grout line and slowly extracting the auger no faster than an equivalent volume of grout is pumped, a continuous column of concrete is formed. A single large reinforcing rod can be installed for the full pile length through the hollow -stem of the auger, and/or a reinforcing cage can be placed in the column of wet grout. SHANNON & WILSON. INC. W-5385-61 Ms. Ursula Schluter March 29, 1990 Page 4 The quality of auger -cast concrete piles is primarily dependent on the procedures and workmanship of the Contractor who installs them. A properly functioning pressure gage and pump stroke counter should be provided on the grout pump to assist in monitoring auger -cast pile installation. The counter is used to determine the approximate volume of grout pumped by counting the number of strokes of a displacement -type pump. The pump should, therefore, be calibrated prior to its use. The pressure gage is used to monitor the pressure of the grout to evaluate the rate at which the auger should be retracted, and if the auger or hoses are plugged. The auger should be withdrawn with slow positive rotation at a slow steady pull and should not be pulled until the grout has been pumped a few feet above the tip. Piers are constructed by drilling a hole with a short, single -flight auger. The auger is connected to a kelly bar which is rotated and lowered in and out of the borehole with a truck- or track -mounted drilling rig. When the hole has been advanced to the required penetration, all loose and disturbed soil at the bottom should be removed with a clean -out bucket which has the same diameter as the drilled borehole. Based on information from the exploratory test pits, it is our opinion that groundwater could be a problem during drilled pier installation at this site. Should caving occur in the loose silts and sands that are present at the site, casing would be needed in the upper portion as appropriate. After the pier has been cleaned and dewatered, reinforcing and concrete are placed in the hole. Reinforcing cages should have hole -centering guides. The concrete should have a slump of at least 6 inches and be placed in the borehole through a funnel or'elephant trunk' in order to prevent the free -falling concrete from hitting the borehole walls and contaminat- ing the concrete. Basement level walls of the proposed structure should be designed for an equivalent fluid pressure of 55 pounds per cubic foot (pcf), plus one pound per cubic foot for each degree of upward incli- nation of the backslope above the wall. Cantilevered retaining walls which are not connected to the SHANNON & WILSON. INC. Ms. Ursula Schluter March 29, 1990 Page 5 W-5385-01 house could be designed for an equivalent fluid pressure of 35 pcf, plus one pound per cubic foot for each degree of upward inclination of the backslope above the wall. These pressures assume the walls are drained so that hydrostatic pressures cannot develop. Recommendations for wall drainage and backfilling are presented on Figure 3. Lateral forces would be resisted by passive earth pressure against the buried portions of structures and by friction against the bottom. In our opinion, passive earth pressures in backfiill could be estimated using an equivalent fluid pressure of 280 pounds per cubic foot (pcf) above the ground- water table and 140 pcf below the water table. These values assume that the structures extend at least 18 inches below the lowest adjacent grade, and the backfill around (below) the structure is a horizontally graded, compacted granular fill. We recommend that a coefficient of friction of 0.5 be used between cast -in -place concrete and soil for non -pile supported structures. Base friction should not be considered beneath pile supported portions of the structure. Because of the large amount of groundwater seepage at this site, development should include the installation of trench subdrains to lower the groundwater level and improve the stability of the site. We expect that one or more trench subdrains will be required, extending approxi- mately north -south across the property near the east property line and again at about the mid point of the property. Depending on the layout of the structure, the footing drains along a day- light basement may function as one or more of the required subdrains. The locations and depths of the subdrains should be evaluated once the locations of the structures are known. A typical trench subdrain installation is shown on Figure 2, and a footing subdrain is shown on Figure 3. The subdrains should consist of slotted plastic pipe surrounded by at least 8 inches of drainage sand and gravel at the bottom of a trench filled with drainage sand and gravel, gradation specifications are presented on Figure 2. Native site soils do not meet the requirements for drainage sand and gravel. SHANNON & WILSON. INC. Ms. Ursula Schluter March 29, 1990 Page 6 W-5385-01 I The trench subdrains should extend at least 5 feet below the existing ground surface and at least to the elevation of any proposed excavation level. It should drain south to the property line and, if possible, should be connected with a tightline to the existing storm water drainage sys- tem which runs up and down the slope near the south property line. Caving of the sides of the trench is likely during installation of the trench subdrain. Installation should begin at the south end and proceed up -slope. It may be necessary to periodically stop work for a day or two to let the site drain before advancing the trench. Footing drains consisting of 4-inch (minimum) diameter slotted plastic pipe should be installed on the upslope side of all retaining or basement walls. Freely draining sand or sand and gravel - should be used as backfill adjacent to walls. Wall drainage and backfill recommendations are presented on Figure 3. The downspout water from the structure should be conveyed to a suitable discharge point, such as the existing storm drainage system, in a tightline. Subsurface drainage and downspout water should not flow onto the ground surface and should not flow into perforated footing drains. Wet Weather Earthwork r The soils at the site are generally moisture sensitive, and will become soft and difficult to work when wet. It would be most advisable to schedule earthwork during the dry weather months. Pile or pier installation and any other earthwork should not be accomplished during periods of heavy rainfall. If fill is to be placed in wet weather or under wet conditions when control of soil moisture content is not possible, the fill should contain no more than 5 percent material passing the No. 200 mesh sieve, by weight, based on the minus 3/4 inch fraction. In addition: a.) Earthwork should be accomplished in small sections and canned through to completion to minimize exposure to wet weather. If there is to be traffic over the exposed subgrade, the sub - grade should be protected with a compacted layer of clean sand and gravel or crushed rock. ISHANNON & WILSON. INC. Ms. Ursula Schluter March 29, 1990 Page 7 W-5385-01 b.) No soil should be left uncompacted so it can absorb water. Soils which become too wet for compaction should be removed and replaced with clean granular material; and, c.) Excavation and placement of fill should be observed on a full time basis by a person expe- rienced in wet weather earthwork to determine that all unsuitable materials are removed and suitable compaction and site drainage is achieved. We recommend that these recommendations for wet weather earthwork be included in the con- tract specifications. WOMM s _ 9 •Ru 1. • _/ 17FORS I wpm: We recommend that we be retained to work with your architect to design the necessary drainage installations at the site and to review the portions of the plans and specifications which pertain to earthwork and foundations to determine if they are consistent with our recommendations. We also recommend that we be retained to monitor earthwork construction, including drainage and drilled pier or augercast pile installations, to determine that the work is accomplished in a suitable manner. The installation of concrete piles or drilled piers should be monitored on a full time basis. This monitoring should include verifying the depth of competent bearing soil and measurement of the volume of grout placed into each pile. The conclusions and recommendations presented in this report are based on site conditions as they presently exist and the subsurface conditions are not significantly different from those indicated in the test pit explorations performed by Earth Sciences or inferred from our site reconnaissance. If during construction, subsurface conditions different from those encountered in the explorations and site reconnaissance are observed or appear to be present, we should be advised at once so -that we can review those conditions and reconsider our recommendations where necessary. If there is a substantial lapse of time between submission of our report and the start of work at the site, or if SHANNON & WILSON. INC. Ms. Ursula Schluter March 29, 1990 Page 8 W-5385-01 conditions have changed due to natural causes or construction operations at or near the site, it is recommended that this report be reviewed to determine the applicability of the conclusions and rec- ommendations considering the changed conditions and time lapse. ' This report was prepared for the use of the Owner or Engineer/Architect in the design of the struc- ture. No soil boring or test pit explorations have been accomplished for this study. Unanticipated conditions are commonly encountered and cannot be fully determined by merely per- forming a site reconnaissance, taking soil samples or making explorations. Such unexpected conditions frequently require that additional expenditures be made to achieve a properly constructed project. Some contingency fund is recommended to accommodate such potential extra costs. We appreciate your continued confidence in our firm, please call if you have any questions. Sincerely, SHANNON & WILSON, INC. N/�.0 cF wasy� G fS •••...... • i Ralph N. Bd!> i .%..• Senior Associate MWP:RNB:TEK Enclosures: Figures 1 - 3 SHANNON & WILSON, INC. Approx 1 ft. On -site Soil Trench Excavation Drainage Sand and Gravel Washed 3/8" Pea Gravel (8" minimum above pipe, 12" on sides, 4" below) 6" Minimum Diameter Slotted Plastic Pipe Trench Bottom and Subdrain Pipe Sloped to Drain Specification for Drainage Sand and Gravel Not to Scale 0 1-1/2 100 3/4 90 to 100 1/4 75 to 100 No. 8 65 to 92 No. 30 20 to 65 No. 50 5 to 20 No. 100 0 to 2 By Wet Sieving Slope To Drain Away From Structure Pavement or 8" Impervious Soil Clean granular backf ill, (See note 1) Excavation Slope " (Contractor's responsibility) 8" Minimum cover of 3/8" gravel over pipe Subdrain Pipe Subdrain Pipes 4" Minimum diameter pperated or slotted plastic pipe; tight joints; sloped to drain (67/100' Min.); Provide cleanouts. 8" Basement or Retaining Wall Damp Proofing Washed 3/8' Pea Gravel or clean sand and gravel Vapor Barrier Weep Holes Floor Slab - :Pea Gravel:.':: •�' �' �' �' :'r.'r.' •::. 6' Min. 1. Wall backfill should consist of freely draining granular soil with no more than 5% (by weight based on the minus 3/4-inch portion) passing the No. 200 sieve( by wet sieving), with no plastic fines. 2. Backfill behind the wall should be compacted with hand - operated equipment. Heavy equipment should not be used as such equipment operated near the wall could increase lateral earth pressures and possibly damage he wall. 3. Backfill should be placed in layers not exceeding 6" loose thickness, and should be densely compacted. Beneath paved areas, compact to at least 951/6of the Modified Proctor maximum dry density (ASTM: D1557.70,). Otherwise compact to 92 % compaction. CITY CLERK l CITY OF EDMONDS . 505 BELL STREET tom{ EDMONDS, WA 98020 ; I -, -F - Ef-- 7 COVENANT OF NOTIFICATION AND INDEMNIFICATION/HOLD HARMLESS I Under the review procedures established pursuant to the State. Building Code, incorporating amendments promulgated by the City of Edmonds, and as a prerequisite to the issuance of a building permit for the construction of a residential structure and attendant facilities, the undersigned OWNERS of property do hereby covenant, stipulate and promise as follows: • Descriptiona Subject Properly.. . Ti•lu covenani -vL 1 �i notification and indemnification/hold harmless relates to a tract .11 of land. at the street address of �J-6 �2(o , -75 AZ street address), Edmonds, Snohomish County, Washington and legally described as: Cn oN i EXCISE TAX siREOUIRED a_ 0 "( n 3 irk i r MCC i.; `Yi. �iC4i�, Snohec�i5 ro��nty Treasurer m i k'tiis Cl~ i EVERS N 'J 2. Notification and Covenant of Notification. The above referenced site (hereinafter "subject site") lies within an area which. has been identified by the City of Edmonds as having a potential for earth subsidence or landslide hazard. The risks associated with development of the site have been evaluated by technical consultants and engineers engaged by the applicant as a part of the process to obtain a building permit for the subject site. The results of the consultant's reports and evaluations of WSS52079A/0006.040.034 -1- 3UILDING WSS/klt 02/08/90 �,� J t� ru 1500FEB 9 - 1"0 the risks associated with development are contained in building permit file number (insert number) on file with the City of Edmonds Building Department. Conditions, limitations, or prohibitions on development may have been imposed in accordance with the recommendations of the consultants in the course of permit issuance. The conditions, limitations, or prohibitions may require ongoing maintenance on the part of any owner or lessee or may require modifications to the structures and earth stabilization matters in order to address future or anticipated changes in soil or other site conditions. The statements and conditions proposed by the OWNERS' geotechnical engineer, geologist, architect and/or structural engineer are hereby incorporated by reference from the contents of the file as fully as if herein set forth. Any future purchaser, lessee, lender or any other person acquiring or seeking to acquire an interest -in the property is put on notice of the existence of the content of the file and the City urges review of its contents. The file may be reviewed during normal business hours or copies obtained at the Planning Department, City of Edmonds, 505 Bell Street, Edmonds, Washington 98020. 3. Indemnification and Hold Harmless. The undersigned OWNERS hereby waive any and all liability associated with development, stating that they have fully informed themselves of all risks associated with development of the property and do' therefore waive and relinquish any and all causes of action against the City of Edmonds, its officers, agents and employees WSS52079A/0006.040.034 WSS/klt 02/08/90 -2- 05220363 E;;; 3; �10l 501 arising from and out of such development. In addition, the OWNERS on behalf of themselves, their successors in interest, heirs and assignees, do hereby promise to indemnify and hold harmless the City of Edmonds, its officers, agents and employees from any loss, claim, liability or damage of any kind or nature to persons or property either on or off the site resulting from or out of earth subsidence or landslide hazard, arising from or out of the issuance of any permit(s) authorizing development of the site, or occurring or arising out of any false, misleading, or inaccurate information provided by the OWNERS, their employees, or professional consultants in the course of issuance of the building permit. 4. Insurance Requirement. In addition to any bonding which may be required during the course of development, the Community Services Director haste (strike one) specifically required the maintenance of an insurance policy for public liability coverage in the amount and for the time set forth below in order to provide for the financial responsibilities established through the indemnification and hold harmless agreement above: (insert insurance requirements and time period, if any --if no insurance required, so state.] WSS52079A/0006.040.034 WSS/klt 02/08/90 3_ 95052 �I , ...K.JU Fu { JJc. 5. Covenant to Touch and Concern the Land. This covenant of notification and indemnification/hold harmless touches and concerns the subject tract and shall run with the land, binding, obligating and/or inuring to the benefit of future owners, heirs, successors and interests or any other person or entity acquiring an interest in property, as their interest may appear. This provision shall not be interpreted to require a mortgagor or lender to indemnify the City except to the extent of their loss nor to obligate such persons to maintain the insurance above required. DONE this day of , 199J OWNERS) i By: By: Y STATE OF WASHINGTON ) ) ss: COUNTY OF Si,-c`i new✓ I certify that I know or have satisfactory evidence that �,/ r(!a zr, signed this instrument and acknowledged WSS52079A/0006.040.034 -4- WSS/klt 02/08/90 05 22 03 63 E;4�UJ f (7 , it to be (his/her) free and voluntary act for the purposes mentioned in this instrument. DATED this"t day of 199-3. NOTARY PUBLICf My commission expires: STATE OF WASHINGTON ) ) ss: COUNTY OF ) I certify that I know or have satisfactory evidence that signed this instrument and acknowledged it to be (his/her) free and voluntary act for the purposes mentioned in this instrument. DATED this day of 199_. NOTARY PUBLIC My commission expires: STATE OF WASHINGTON ss: COUNTY OF ) I certify that I know or have satisfactory evidence that signed this instrument, on oath stated that (he/she) was authorized to execute the instrument and acknowledged it as .the (title) of (name of party on behalf of whom instrument was executed) to be the free and voluntary act of such party for the uses and purposes mentioned in this instrument. DATED this day of , 199_. WSS52079A/0006.040.034 WSS/klt 02/08/90 NOTARY PUBLIC My commission expires: -5- th C. 189" CITY OF EDMONDS 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771.0220 • FAX (425) 771.0221 DEVELOPMENT SERVICES DEPARTMENT Planning • Building • Engineering April 9, 1999 Ursula Schluter 15620 751h Place West Edmonds, Washington 98026 RE: Homeowner Insurance Coverage for Meadowdale Development BARBARA FAHEY ' MAYOR As you may recall, development of your home was subject to Edmonds Community Development Code (ECDC) Chapter 19.05.050 which regulated construction and insurance coverage requirements for all designated Meadowdale Landslide Hazard Area development. The purpose of this letter is to inform you that the Edmonds City Council has enacted a change which effects your homeowners policy that was required by this ordinance. If you recall you were required to post a one million dollar homeowner policy in order for your home to be granted final occupancy. Please be advised, the City Council has repealed this requirement effective April 16, 1999. In lieu of this policy the City Council will be holding future public hearings to determine alternate coverage methods to ensure that the intent of ECDC 19.05.050 are still met. Please contact the City Clerk if you are interested in attending these meetings. You may wish to consult your insurance professional to determine the proper amount of insurance coverage necessary to meet your specific needs. Since the insurance requirement is repealed the City no longer requires to be informed of your coverage or be provided with a copy of your current policy. Please feel free to contact me if you have any questions at 771-0220. Thank you, (/� X�J Jeannine L. Graf Building Official Incorporated August 11, 1890 Sister City - Hekinan, Japan M.S. Ursula 8chlutcr 21701 801h Avenue VVAaxt, #4 Edmonds, %ahington 98020 y�Wo�C Ck /e� � RF. MANVORING OF SMDRAIN INSTALLATION, MOPOSED RE SI EW3r, 1=0 75'I H FLACE WEST, l�s'.DMONDS, WABHING'1C1N PERMIT NO 949M Dear Ms. 9chulter; Between October 21 and October 27, 1994, we made several visits to thg site to monitor dw Installation of the trends subdrain at your proposed residamce at 13620 75th Place Wort In Edmonds, Washington. The dtains cmxi+lW of slotted, plastic pipe installed. in the bottom of gravel tilled trenches at selected locations to intemept and renwve groundwater Boom the site. The vmrk was done by North Coast Construction. At out recommendation, two dtaln lines were installed: oaa was located in the storm VA"r detention excavation, approximately 2 fiu4 below the storm water detention pips; the aeoond extends up the slope alatg the south property lice and crosses the site parallel to rho elope contours, hetwem the proposed foundation pile locations (tv be installed in the epilog of 1991). Roth drabaage trenches flow to the k wee catch basin along the aobth side of the property. Groundarater wits present in the trench ex=Qtions, partioularly in tho vicinity of the storm va-Ater detention system, Water was fic%ina from the oorapleted subdrain system at a We of 4 eel S gallons per minute on Ockibw 28, 1994. Native virtue and straw wmrc spread across the sate as errosion protootion following completion of the earthwork. 44'rNOnyl 114T1 r 9rNtc r - 3uiTc im t;N'.•1':U•tYa(1 FA1(ipn.q?a.HJI� owus (904) iCvd t91fo-Us (906 W-3385 02 sattieE* VAk SONOM U - 9N',M 3- rW3AV H1AY t811Z ininiHa9 b7f19»t1/Noma ivnelA UOULN00 :1SV:l1d'XVd s[H1. HAtM W40160kld ANV 3AVH nGk 3t • 3t7v9g3W 0 - IZ4 133HSWan00 Xa:J -- N O 1 S 3(3-ib n S 1 A :ai A�H1V1 3wt�n l�3At,3Q �A�1� 317dQ Tod Wd20,6 trW LT iStO ZL9 9W 'CH 3NDHd d3in-H-i38 u-ris H1 w-vs3a wsin : wo.ld From' : U f SUAL DES 194 URSULA E2 PHONE No. : 206 672 0851 • Nov. 17 1994 Q : 03PIl P01 Ms. Ursula Schluter SHANNON6WILSCM.INC. November 15. 1994 Page 2 Bawd on our obscrvations at the site, it is our opinion that the work waa accomplished in accordance with our rocommendtdons and tho approved plans and apacit3oations. We appreciate the opportunity to be of service, Sincerely, SHANNON Ar W I SON, Mr. Ralph N. Boirum, P.E. Staff Consuluant RNB:TEK/rnb w5M5-D2.LTtM3854kd/1kd W-5385-02 0 • W-5385-02 SHANNON & WILSON, INC. Geotechnical and Environmental Consultants 400 North 34th Street, Suite 100 • P.O. Box 300303 • Seattle. WA 98103 • (206) 632-8020 -Fax: 633-6777 DAILY MEMORANDUM Date: October 24, 1994 To: Ms. Ursula Schluter Permit # 940703 21701 80th Avenue West #4 Edmonds, Washington 98020 RE: CONSTRUCTION MONITORING, SUBDRAIN INSTALLATION, PROPOSED RESIDENCE, 15620 75TH PLACE WEST, EDMONDS, WASHINGTON, PERMIT NO 940703 I visited the above project site on October 24, 1994 to observe installation of the trench subdrain. At the time of this visit, the contractor had installed the storm water detention system and was excavating up the south property line for the upper drain. A 4-inch diameter, slotted plastic pipe had been installed in washed 3/8-inch pea gravel about 2 feet below the storm water detention system, as per my recommendation. That section of drain appeared to be flowing clear water and functioning properly. I discussed the location and depth of the upper subdrain with the contractor and observed as part of it was excavated. Because the first section of subdrain extending upslope from the catch basin was tightline, water in the lower part of the trench could not get into the catchbasin. I recommended that a new opening be made in the catch basin and an 8 to 10-foot length of slotted pipe be installed in the lower part of the trench to collect and remove any water from that area. -,�2 . � - Ralph N. Boirum, P.E. Staff Consultant cc: City of Edmonds • W-5385-02 SHANNON & WILSON, INC. Geotechnical and Environmental Consultants 400 North 34th Street. Suite 100 • P.O. Box 300303 • Seattle. WA 98103 • (206) 632-8020 -Fax: 633-6777 DAILY MEMORANDUM Date: October 20, 1994 To: Ms. Ursula Schluter 21701 80th Avenue West #4 Edmonds, Washington 98020 BUILDING Permit # 940703 NOV 21 1994 RE: CONSTRUCTION MONITORING, SUBDRAIN INSTALLATION, PROPOSED RESIDENCE, 15620 75TH PLACE WEST, EDMONDS, WASHINGTON, PERMIT NO 940703 I visited the above project site on October 20, 1994 to observe installation of the trench subdrain. At the time of this visit, the contractor had cleared brush from the work area and begun excavation for the storm water detention system. Soils exposed in the storm water detention excavation consisted primarily of silty clay and clayey silt. The trench was 3 to 6 feet deep, and bottom of the excavation appeared too be in very stiff to hard native clayey silt. Considerable seepage was emerging from a sandy zone above the silt in the north half of the trench. The upper 2 to 3 feet of exposed soils appeared to be fill. I recommended that the storm water detention excavation be utilized as a trench subdrain by installing a 4-inch diameter slotted plastic pipe in its bottom and backfilling it with pea gravel. I recommended that an additional subdrain line be installed up the south property line to point where it could turn north and pass between rows of foundation piles. (.,. - "- J// /i, - " � � Ralph N. Boirum, P.E. Staff Consultant cc: City of Edmonds 890 _ 19C, CITY OF EDMONDS 250 - 5TH AVE. N. • EDMONDS, WA 98020 • (206( 771-0220 • FAX (2061 771-0221 COMMUNITY SERVICES DEPARTMENT Public Works • Planning • Parks and Recreation • Engineering October 24, 1994 Ms. Ursula Schluter 21701 80th Avenue West, ##4 Edmonds, Washington 98026 RE: SFR @ 15620 75th Place West LAURA M. HALL MAYOR At the recommendation of your Geotechnical Engineer, Mr. Ralph N. Boirum P.E. of Shannon & Wilson, the City shall grant your request to immediately install the approved trench subdrain system at the subject project. This request is granted due to special circumstances with regard to the unusually dry weather this area has experienced over the last several months. The work is scheduled to be complete by November 5th, 1994. If this completion date cannot be met Mr. Boirum shall inform the City in writing as to his recommendation to proceed past this date. As you are aware, special inspection by Mr. Boirum or another licensed engineer under his supervision, is required. Daily field reports must be submitted to the City for review and approval. Any deviation from the approved plan shall be highlighted under separate cover. All site erosion control measures shall be installed prior to the start of work and the approved drainage plan must be on -site while your contractor is working. Thank you, eannine L. Graf Building Official cc: Engineering Dept Street File • Incorporated August 11, 1890 a Sister Cities International — Hekinan, Japan • STR EET R L E- • BUILDING ® SHMNON 8WILSON, INC. FAIRBAE � � 1994 Fti��°N°S ® GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS ANCHORAGE SAINT LOUIS BOSTON March 30, 1994 ' iW4 Ms. Ursula Schluter 21701 80th Avenue West, #4 Edmonds, Washington 98020 RE: SECOND SUPPLEMENTAL GEOTECHNICAL REVIEW, PROPOSED RESIDENCE AT LOTS 1 AND 2, 75TH PLACE WEST, EDMONDS$ WASHINGPON Dear Ms. Schluter: In response to Landau Associates' second supplemental geotechnical review of the Proposed Schluter Residence at 15620 75th Place West in Edmonds we offer the following: 1. We recommend a minimum of 1 foot of native soil backfill at the top of the proposed trench subdrain. Additional native soil may be used as backfill, depending on the depth of seepage zones encountered in the trench excavation. In general, we recommend that freely draining granular soil be used to within about 3 feet of the ground surface to provide adequate site drainage. We expect that Shannon & Wilson, Inc. personnel will be at the site during construction to make field decisions regarding the use of backfill materials. 2. Shannon & Wilson agrees with the Landau recommendation regarding construction of a dam in the subdrain trench where a perforated line transitions to tightline, and intends to have such dams installed at appropriate locations. 3. The blocky, disturbed appearance of the sample taken at a depth of 60 feet in boring B-1 was evaluated during foundation studies for the proposed project. The observed sample disturbance could be the result of landsliding or of stress relief associated with glacial recession and hillside erosion. Such disturbance is common in Lawton and Whidbey clays and can rarely be directly associated with instability. The area has a history of sliding and it is reasonable to assume that disturbed soils are present throughout the Meadowdale area. Assuming that this disturbed soil is a result of landsliding, it is likely that the conditions which resulted in that sliding event no longer exist; i.e., the geometry of the area has been changed by additional sliding and erosion and construction of the seawall and railroad embankment, and hydraulic conditions have been changed by development in the area and the installation of sewers, drains and other utilities. The presence of this soil was considered in our W-5385-02 400 NORTH 34TH STREET -SUITE 100 P.O. BOX 300303 SEATTLE. WASHINGTON 98103 206.632.8020 FAX 206.633.6777 • Ms. Ursula Schluter. March 30, 1994 Page 2 SHANNON 6WILSON, INC. assessment of the stability of the site. As stated in our report, in our opinion, once this site is developed in accordance with our recommendations, the probability of substantial loss due to future sliding will be less than 30 percent in a 25 year period, in our opinion. We appreciate the opportunity to be of service. Sincerely, SHANNON & WILSON, INC. �)/ ,sv/T7 Ralph N. Boirum, P.E. Senior Associate RNB:TEK/rnb W5385-02XT5/W5385-1kd/1kd W-5385-02 LANDAU ASSCC—MATES, AN e� --. Environmental and Geotechnical Services City of Edmonds 250 5th Avenue North Edmonds, WA 98020 Attn: Ms. Jeannine L. Graf AUK 93 August 24, 1993 RE: SUPPLEMENTAL GEOTECHNICAL REVIEW PROPOSED SCHLUTER RESIDENCE LOTS 1 AND 2, BLOCK 28 OF THE PLAT OF MEADOWDALE BEACH 15620 75TH PLACE WEST MEADOWDALE AREA EDMONDS, WASHINGTON In accordance with your request, we have completed a supplemental geotechnical review of resubmitted documents concerning the above -noted proposed residence. Our review was conducted using City Ordinance No. 2661 as the standard for comparison. A list of the resubmitted documents we reviewed is included as Attachment 1. Landau Associates performed a preliminary geotechnical review of the initial submittal, the results of which are presented in our letter to the City dated March 11, 1993. In our March 11, 1993 letter, we identified several issues that needed to be addressed by the design professionals in order to meet the requirements of Ordinance 2661, and to resolve inconsistencies between the submitted plans and other documents. Our supplemental review indicates that the plans have been revised to incorporate some requirements of the ordinance that were omitted in the previous submittal. However, the revised plans still do not completely satisfy the requirements of the ordinance, nor does the Geotechnical Engineer's response resolve concerns raised in our preliminary review regarding characterization of site subsurface conditions and construction related issues. Our supplemental review indicates that there are several ordinance requirements that, in our opinion, may require additional attention. These requirements are briefly summarized as follows: 08/24/93 jAEDM0NDS\SC1-iUJTR2.LTR P.O. BOX 1029 EDMONDS, WA 98020-9129 - (206) 778-0907 • FAX (206) 778-6409 SPOKANE: (509) 327-9737 o FAX (509) 327-9691 / TACOMA: (206) 926-2493 o FAX (206) 926-2531 • The Environmental Checklist states that no impervious areas will be created, no vegetation will be removed, and that sediment and erosion control will be left up to the geotechnical engineer during construction. These statements, as well as others, remain inconsistent with the plans and other submitted documents. The lead design professional, Mr. Phillip L. Brown, AIA, should resolve any inconsistencies within required documents. • Ordinance 2661 requires a tree cutting plan prepared by a registered forester or licensed landscape designer. A formal tree cutting plan properly stamped and containing the required items was not provided for our review. It is unclear from the previously submitted topographic map or the current site plan if the proposed construction will require tree cutting. Based on our informal knowledge of the site, some clearing and tree cutting are distinct possibilities. Ordinance 2661 requires a grading plan prepared by a licensed architect or engineer. The current revised plans indicate that finish grading will involve limited filling for construction of the driveway. However, a formal grading plan properly stamped and containing the required items, including volume calculations, was not provided. Given the configuration and topography of the site, it is our opinion that construction of the proposed residence could pose a significant challenge in terms of site preparation and grading. Critical issues related to site preparation and grading include access for construction equipment, clearing activities, excavation for the proposed trench drain and the storm water system, foundation augering, disposal of excavated soil, temporary and permanent erosion control, temporary shoring, and the impact of grading activities on adjacent properties. These are issues which should be addressed by a formal grading plan. Ordinance 2661 requires a drainage plan prepared by a licensed engineer. The current revised plans include a storm water system and a limited set of calculations in support of the indicated system. The design has not been stamped by a licensed engineer in accordance with ordinance requirements. In addition, the drainage system discharges to an existing catch basin located on property immediately to the south of the site. Connection to this catch basin may require an easement from the owner of the property on which the catch basin is located. The Ordinance also requires that Burlington Northern Railroad (BNR) provide documented approval of any drainage plan which may impact their property. Since the drainage system discharges through BNR property, the applicant may need to assess the potential impact of drainage discharges on BNR property and possibly obtain BNR approval. • Ordinance 2661 requires a site -specific geotechnical report supported by field explorations and analyses of soil characteristics performed by, or under the supervision of, the Geotechnical Engineer. Shannon & Wilson did not conduct explorations of the site, relying instead on assumptions and a review of exploration data provided in the Earth Sciences' March 21, 1986 geotechnical report (for an unrelated project). (In that report, Earth Sciences specifically 08/24/93 J:\EDM0NDS\SCHLUTR2.1.TR 2 LANDAU ASSOCIATES, INC. 0 excluded future owners of the site from using that information.) Shannon & Wilson's May 7, 1993 letter notes that they did not rely on data generated by Earth Sciences for their foundation and drainage design. Since the Earth Science's data was not used, and since Shannon & Wilson did not perform a site/project-specific investigation, it is our interpretation that ordinance requirements have not been met. • Ordinance 2661 requires that the geotechnical report include a map showing the location of site explorations. If the Earth Sciences test pit information is to be used, Shannon & Wilson must show exploration locations relative to the proposed building footprint. • Ordinance 2661 requires that the geotechnical report include recommendations regarding the possible need for flexible utility connections at points of_entry to structures. The 1990 Shannon & Wilson report does not address this issue. Ordinance 2661 requires that both the geotechnical report and the geotechnical declaration include an evaluation setting forth the statistical probability of earth movement within a 25-year period. Shannon & Wilson has not provided an assessment of probable risk in either the geotechnical report or their geotechnical declaration, or in their review and response letters dated July 17, 1992 and May 7, 1993, respectively. A statement regarding statistical probability of movement is required. Ordinance 2661 requires that recommendations for grading and earthwork address shoring requirements during construction. Excavation for the proposed trench drain may extend to considerable depth through slide material, and will likely require shoring. Shannon & Wilson's assertion in their May 7, 1993 letter that shoring is the responsibility of the contractor is not entirely consistent with the intent of the Ordinance, in that an engineering description of soil/groundwater conditions is typically provided to the contractor for his use in properly scoping/bidding the job. In their 1990 report, Shannon & Wilson provided lateral earth pressure criteria, but did not address pile lateral capacity. In the absence of stated geotechnical design criteria or structural design calculations, it is unclear whether the current pile design adequately addresses the effects of lateral pressures due to potential earth movement. Since site soil conditions are uncertain, the City may wish to consider requesting and reviewing calculations for the pile foundation system. • Ordinance 2661 requires that a site geotechnical evaluation involving geologic evaluation or interpretation shall be reviewed and approved by a geologist. We suggest that the City require such a review. The reviewing geologist should be familiar with complex large-scale landslides such as the Meadowdale Landslide. 08/24/93 J:\EDM0NDS\SCHLUTR2.LTR 3 LANDAU ASSOCIATES, INC. In summary, while we do not take issue with the proposed approach to site development and foundation support, we believe that the concerns identified in our preliminary review regarding the present understanding of site subsurface conditions remain valid. In the absence of adequate subsurface information, it is our opinion that the risks associated with the proposed development cannot be sufficiently evaluated. This was apparently the conclusion reached by Earth Sciences in their 1986 report. In that report, Earth Sciences advised against developing the upper, or eastern, portion of the site, and offered their opinion that ordinary wood and concrete piles could not develop adequate lateral capacity in the slide material. Earth Sciences further concluded that construction in the upper portion of the site could increase the risk of site instability to greater than 30 percent within a 25-year period. Without obtaining additional site - specific information, Shannon & Wilson has apparently arrived at a different interpretation of the potential impact of the proposed development on site stability. It is unclear from the documents provided for review whether the proposed piles have sufficient shear and bending capacity to resist lateral earth forces, and if sufficient moment capacity has been provided at the top of the piles. We concur that reducing site groundwater levels could improve site stability. However, we have reservations regarding the overall effectiveness of the trench drain as proposed. Based on the limited subsurface information available, it appears that the trench could be excavated to depths in excess of 16 ft, or more, in order to intercept groundwater. In addition, the slide material appears to be relatively fine-grained, and the proposed trench may not create an effective influence zone capable of inducing significant drainage from the surrounding slide material. In their May 7, 1993 letter, Shannon & Wilson stated that construction of the BNR wall along the toe of the slope improved the stability of the site, and that the site has been stable since the wall was constructed. While the wall may have helped site stability, we caution against including the wall in evaluation of site stability. It is our understanding, based on the 1990 Shannon and Wilson report, that the wall was not designed or intended to perform as a retaining structure, but as a means of collecting debris. Also, the wall is not on the Schluter property and is, therefore, dependent on maintenance by the Railroad. If the wall should deteriorate or fail, BNR would not be obligated to repair or restore it, and the property stability could be negatively affected. We would also caution against assuming that the site has been stable since the wall was built. Several localized slides were reported as having occurred in the vicinity of the property in the early 1970's and, since the year of wall construction has not been 08/24/93 I:\EDM0NDS\SCHLUTR2.LTR 4 LANDAU ASSOCIATES, INC. documented, it is unclear whether or not movement occurred after the wall was built. Based on local slide history, it is conceivable that the wall, or portions thereof, could be second or third versions of the original. We recommend that the plans and other submitted documents be returned to the applicant for further action. In addition, the Geotechnical Engineer should evaluate and comment further on specific issues raised herein. We would be pleased to discuss with the design professionals the issues noted above. Please note that Landau Associates did not review structural calculations or verify drainage calculations. Please call if you have questions concerning this review, or require the services of Landau Associates for subsequent review services. WDE/JWG/bb No. 74042.10 3 copies submitted Attachment 08/24/93 JAEDM0NM\SMLUTR2.LTR 5 LANDAU ASSOCIATES, INC. By: V, William D. Evans, CPG Project Manager and UU /d4W Wade Gilbert, PE Project Engineer LANDAU ASSOCIATES, INC. • ATTACHMENT 1 • Sheets Al through A5, and Sl through S2 of Plans for New Residence for Ursula Schluter, Philip L. Brown, Architect, dated January 26,1993 and revised August 1993. • Response Letter, Proposed Schluter Residence,15620 75th Place West, Shannon & Wilson, Inc., dated May 7, 1993. 08/24/93 J:\EDM0NDS\SC11LUTR2.LTR LANDAU ASSOCIATES, INC. 188TREET RLia Copy E111 SHANNON IWILSONs INC.SEATTLE NTS FAIREIANKS ANCHORAGE RSAINT MUIS May 7, 1993 �C� f �� JUG ? 393 I Ms. Ursula Schluter O 1 PERMIT 7 -278+ 80th Avenue West #4 COUNTER Edmonds, Washington 98020 RE: PROPOSED SCffi.UTER RESIDENCE, 15620 75TH PLACE WEST, EDMONDS, WASHINGTON We have reviewed the letter to the City of Edmonds, dated March 11, 1993; by Landau Associates, Inc., regarding their review of your plans for the proposed Schluter residence at 15620 75th Place West in Edmonds, Washington. In response to that letter we offer the following: The soil conditions described from the 1986 Earth Sciences test pit logs were useful in that they tend to confirm our understanding of the soil conditions in the area and provide data specific to the subject site. Our recommendations do not rely on the accuracy or detail of those explora- tions, however, as Shannon & Wilson, Inc. will confirm the actual soil conditions at the site during construction of the trench subdrain system and installation of the foundation piles. Both the design of the drainage system and the depth of the piles will be modified as appropriate at that time so that the needs of the project are met. The stability of the Schluter property was increased by construction of the retaining wall along the toe of the slope by Burlington Northern Railroad, and the property has been stable since that wall was constructed. Lowering of the ground water level by the proposed dewatering system will further increase the stability of the site. In our opinion, installing a piezometer to measure porewater pressures is not necessary and would produce no information which is useful at this time. As long as there is no sliding there is no way of knowing or calculating with any degree of certainty the factor of safety against sliding on the hillside. The geotechnical engineer must assume that at the least stable time in the recent history of the site (normally the wettest time of the wettest year) the factor of safety was slightly above 1.0. The site must then be developed in such a way that the stability of the site is further increased. Once a slide develops, the factor of safety of the slope is known (it is 0.999...9,) and the piezometric level in the soil near the failure plane is an important parame- ter to be used in the slide analysis. However, the piezometric level is not particularly useful until there is a slide to analyze. Ground water was observed to seep from the ground surface during our reconnaissance of the site, indicating that the piezometric level was (s) at or above the ground surface. The proposed trench subdrain will lower the ground water level and prevent it from ever reaching the level W-5385-02 400 NORTH 34TH STREET -SUITE 100 P.O. BOX 300303 SEATTLE. WASHINGTON 98103 41 tip, Ms. Ursula Schluter SHANNON MMILSON. INC. May 7, 4993 Page 2 to which it now exists, thus preventing the factor of safety from dropping to its previous lowest value. Zbere are always risks associated with sloping terrain due to the inherent subterranean unknowns. We have endeavored to provide recommendations for design and construction which . will minimize those risks in a reasonable and cost effective manner. Ms. Schluter has indicated that she is aware of and prepared to accept the risks associated with building and living on hillside property. In response to comments on page 3 of the Landau letter, site access, temporary cut and fill slopes and construction shoring will be the responsibility of the contractor, who must work in compli- ance with WAC 296-155. Grading at the site will be minimal and will have no long term effect on the site stability. The soils an the site are only moderately erodible, and erosion can be controlled by implementation of the wet weather earthwork recommendations presented in our report dated March 19, 1990, and through the judicious use of straw bales and/or geotextile silt curtains. Most of the soils excavated during the trench subdrain installation will be removed from the site. A stated in our January 29, 1993 letter, Shannon & Wilson, Inc. has reviewed the geotechnical aspects of the plans for the proposed house and found them in general accor- dance with our recommendations. We appreciate the opportunity to be of service. Sincerely, SHANNON & WI SON, INC. EXPIRES 7R5/ 13 s /� 3 Ralph N. Boirum. P.E. Senior Associate RNB:TEK/rnb W53&5-03. 3VJW5385-1kd/lkd W-5385-02 CA�j • GROUP FOUR, Inc. 16030 Juanita -Woodinville Way N.F. Bothell, Washington 98011 FAX (206) 362-3819 (206) 775-4581 • (206) 362-4244 April 12, 1993 Ms. Jeannine L. Graf City of Edmonds 250 5th Avenue North Edmonds, WA 98020 Group Four Job No. 90-3010 Dear Ms. Graf: NVILD04 Op I � 1993 Pursuant to our conversation Tuesday, April 6th. I am writing to explain the difference between the Schluter topographic survey prepared by Group Four and the topographic survey prepared by Darrell Ford & Associates for the Spiro residence across the street. On April 8th, I contacted Mr. Ford about his survey and discussed with him how it was prepared. His survey is based on a invert elevation of a sewer manhole in front of the Spiro residence. This is shown as manhole No. 63 on his map. The elevaticn shown is 113.53 feet for the invert. Our survey was based on Mean Lower Low Water (M.L.L.W) per bench marks established by R.M.A. & Associates for aerial control in the area. The two topographic surveys have an equation of + 15.14 feet. Once having subtracted 15.14 feet of Darrell Ford's topographic survey to match Group Four's topographic, the two surveys match very well. I hope that this explains in enough detail to enable you to understand and relate the surveys to each other. If I can be of further assistance please don't hesitate to contact me anytime. Sincerely, GROUP FOUR, INC. �y Dan Roupe Vice President Surveying cc: Ursula Schluter SURVEYING ENGINEERING PLANNING MANAGEMENT • is April 4th 1993 City of Edmonds Mr. Addison L. Chrisman IV Engineering Inspector 250 5th Ave N Edmonds Wa. 98020 Re: Letters dated March 26thl30th Dear Mr. Chrisman, Rlr GVl,VS0 RJR - � 1993 ING Sorry I was not able to respond earlier. I am in the process of inquiring about the bond. I understand there is a form .iaich the bond company needs from the city. I would very much appreciate if you could send several. I am aware the engineering division might have to be last to sign off. Changes are still beeing made at this point and I can not purchase a bond (non-refundable) for a project that is still not 100% sure. In re to the sidewalk, if I should decide to construct it with the house, what requirements would the city have? Sincerely, Ursula Schluter cc Phillip Brown 890 19y CITY OF EDMONDS LAURA M. HALL 250 - 5TH AVE. N. • EDMONDS, WA 98020 • (206) 771-0220 • FAX (206) 771-0221 MAYOR HEARING EXAMINER FINDINGS AND DECISION OF THE HEARING EXAMINER OF THE CITY OF EDMONDS IN THE MATTER OF THE APPLICATION FILE: OF URSULA SCHLUTER FOR APPROVAL OF A VARIANCE V-93-11 DECISION: The variance is granted subject to conditions listed. INTRODUCTION Ursula Schluter, 21701 - 80th Avenue West, #4, Edmonds, Washington 98026 (hereinafter referred to as applicant) , requested approval of a variance for an increase in the maximum permitted height allowed for a structure in an RS-20 zone and a variance from the setback standards for RS-20 zoned property. The request for the variances is for the property at 15620 - 75th Place West, Edmonds, Washington. A hearing on the request was held before the Hearing Examiner of the City of Edmonds, Washington, on April 1, 1993. At the hearing the following presented testimony and evidence: STEPHEN BULLOCK Planning Dept. City of Edmonds Edmonds, WA 98020 PHILLIP BROWN 15010 N.E. 9th Place Bellevue, WA 98007 At the hearing the following exhibits were submitted and were admitted as part of the official record of this proceeding: Exhibit 1 - Staff Report with the following attachments: A. Vicinity/Zoning Map B. Application C. Site Plan D. Elevation and floor plans E. Critical areas checklist G. Environmental memorandum H. Environmental checklist I. Environmental determination J. Comments from Engineering Department K. Comments from Fire Department L. Comments from Parks Department 0 Incorporated August 11, 1890 • Sister Cities International — Hekinan, Japan HEARING EXAMINER DECISION RE: V-93-11 4/14/93 Page 2 Exhibits continued: M. Comments from Public Works Department. After due consideration of the evidence presented by the Applicant, and evidence elicited during the public hearing, the following Findings of Fact and Conclusions constitute the basis of the decision of the Hearing Examiner. FINDINGS OF FACTS 1. The applicant is the owner of the property at 15620 - 75th Place West, Edmonds, Washington. She seeks variances from the maximum height standards for structures on the property and from the setback standards. 2. The subject property is zoned RS-20. It has a land use designation as set forth in the Comprehensive Plan as low -density residential. The lot is located in the middle of the area of the City of Edmonds. 3. It is the intent of the applicant to develop a residence on the property. Because of the slope conditions of the lot the requested variances are needed. 4. It is the intent of the applicant to develop a bridge and driveway off 75th Place West. Because it will be considered a structure attached to the house, it is subject to the zoning standards of RS-20 zoned property. As a result, it is necessary for the applicant to secure a variance from the street setback standards. The applicant seeks a zero foot setback. 5. The Meadowdale area contains steep and unstable slopes. The subject property has a steep slope between 75th Place West (which it fronts) and the Burlington Northern Railroad right of way immediately to the west. As a result of the steep slopes, it is necessary for the applicant to develop the property as close to the 75th Place West right of way as possible. As a result, the applicant needs a setback variance to access the house via a driveway bridge to the garage. In addition, a height variance is needed to reduce the slope of the driveway bridge from the property line to the garage. 6. In order for a variance to be granted within the City of Edmonds, the criteria of the Edmonds Community Development Code (ECDC) 20.85.010 must be satisfied. These criteria include: HEARING EXAMINER DECISION RE: V-93-11 4/14/93 Page 3 A. Because of the special circumstances relating to the property, the strict enforcement of the zoning ordinance would deprive the owner of use rights and privileges permitted to other properties in the vicinity with the same zoning. B. The approval of the variance would not be a grant of special privilege to the property in comparison with the limitations upon other properties in the vicinity with the same zoning. C. The approval of the variance will be consistent with the Comprehensive Plan of the City of Edmonds. D. The approval of the variance will be consistent with the purposes of the zoning ordinance and the zone district in which the property is located. E. The variance as approved or conditionally approved will not be significantly detrimental to the public health, safety and welfare or injurious to the property or improvements in the vicinity and same zone. F. The requested variance is the owner the rights enjoyed vicinity with the same zoning. (ECDC) the minimum necessary to allow by other properties in the 7. A twenty-five foot street setback is required for RS-20 zoned properties. This requirement is pursuant to the provisions of ECDC 16.20.030. 8. The subject property is undeveloped. However, because of the steep and unstable slopes and the limitation of development on the west end of the site, there is a need for a variance from the street setbacks. 9. The single family residence can be developed to all other setbacks of RS-20 zoned properties. However, the proposed bridge that will provide access from the garage to the house must be developed within the setback. Without the setback variance, access to the structure will be limited. 10. ECDC 16.20.030 establishes the maximum height of twenty-five feet for the primary structure on site. This height standard is established by measuring from the average existing grade of the proposed building footprint. Because of the slopes of the site, the average grade is significantly lower than if the property were i HEARING EXAMINER DECISION RE: V-93-11 4/14/93 Page 4 developed on level land. As a result, a variance is needed in order for the applicant to develop the structure. 11. The residence will have the garage on the top floor of the structure. The structure will have a flat roof and will be approximately one foot below the street level of 75th Place West. However, a variance of an additional three feet in height is needed in order to provide an accessible driveway and garage at a slope that is within the code. 12. Special circumstances that exist on the subject property to necessitate the grant of the variance from the setback standards and the height standards include the steep slope of the site. The severity of the slope creates limitations on the development of the site and restricts access to the site by car. With the use of the setback variances and the height variances this access can be achieved. 13. The grant of the variance will not be a grant of a special privilege. It is allowance of the applicant to develop the property in a manner similar to other properties that have been developed in the area. The other properties in the area also have severe slope issues. 14. The grant of the variances will not be contrary to the intent of the zoning code or the Comprehensive Plan. The variances will allow the site to be developed with a single family structure consistent with the Comprehensive Plan designation of low -density residential. 15. The requested variances will not be detrimental to other properties in the area. It will not block views and will not create disruptions for the enjoyment of other properties. 16. The requested variances appear to be a minimum variance request. 17. No adverse testimony was received at the public hearing. 18. The applicant indicated that special engineering will be required to develop the site. These will include piers/pilings. 19. The Planning Department of the City of Edmonds recommended approval of the variances subject to the conditions listed in the Staff Report (admitted as exhibit one). 20. The subject property is designated as part of the critical areas of the City of Edmonds and is subject to the review of ECDC 20.15(b). The applicant submitted a critical areas checklist and i HEARING EXAMINER DECISION RE: V-93-11 4/14/93 Page 5 the City issued a waiver from the requirements to prepare a critical areas study. As a result, the applicant has satisfied the critical areas review requirements. 21. The City of Edmonds was designated the lead agency for the environmental review of the proposal. A determination of nonsignificance was issued by the City on March 23, 1993. As the date of the hearing, no appeal had been filed of the DNS. CONCLUSIONS 1. The application is for the approval of variances from the setback standards and height standards for RS-20 zone for the development of a residence at 15620 - 75th Place West, Edmonds, Washington. The requested variances are for a increase in the maximum height in the structure from twenty-five feet to twenty- eight feet and a allowance of a construction within the street setback. The street setback variance requested is zero. 2. In order for a variance to be granted within the City of Edmonds, the criteria of ECDC 20.85.010 must be satisfied. These criteria have been identified in the Findings of this document and the manner in which they are satisfied has also been addressed. The Findings relating to the manner in which the criteria are satisfied are hereby adopted as the Conclusions in support of the variances. 3. The Hearing Examiner of the City of Edmonds has jurisdictional authority to hold a hearing and to issue a decision based on the authority granted in ECDC 20.100.010(b). DECISION Based upon the preceding Findings of Facts and Conclusions, the testimony and evidence submitted at the public hearing, and upon the impressions of the Hearing Examiner at a site view, it is hereby ordered that the requested variances for the development of the property at 15620 - 75th Place West, Edmonds, Washington are granted subject to the following conditions: 1. The height variance for the development of a single family residence on site is granted. The height of the structure shall not exceed twenty-eight feet. 2. The street setback for the development of the subject property is reduced to zero feet. The street setback shall be for the development of the driveway/bridge to provide HEARING EXAMINER DECISION RE: V-93-11 4/14/93 Page 6 access. off 75th Place West. The actual residence on the subject property shall not be developed within the street setback. 3. This application is subject to the applicable requirements contained in the ECDC. It is the responsibility of the applicant to ensure compliance with the various provisions contained in these ordinances. Attachments 9 through 12 are provided in this report to familiarize the applicant with some of the additional development regulations. These attachments do not include all of the additional regulations. 4. The applicant shall obtain a building permit prior to construction. 5. The permit should be transferable. Entered this 14th of April, 1993, pursuant to the authority granted the Hearing Examiner under Chapter 20.100 of the Community Development Code of the City of Edmonds. J S M. DRISCOLL ring Examiner NOTICE OF RIGHT TO APPEAL Written appeals alleging specific error of fact or other grounds for appeal may be filed with the Planning Department, City of Edmonds, Civic Center, Edmonds, Washington 98020, within fourteen (14) days of the date of the Hearing Examiner's final action. In this matter any appeal must be received by the Department prior to 5:00 p.m. on April 28, 1993. M ' V • GROUP FOUR,Inc. 16030 Juanita -Woodinville Way N.E. Bothell, Washington 98011 FAX (206) 362.3819 (206) 775-4581 • (206) 362-4244 March 29, 1993 Ms. Jeannine L. Graf City of Edmonds 250 5th Avenue North Edmonds, WA 98020 Re: Schluter Residence Group Four Job No. 90-3010 Dear Ms. Graf: STREEPRUE 901010 ��p u 11993 I am writing -to you in response to a letter that was prepared by Landau Associates dated March 11, 1993. The subject of this letter being the Schluter residence in the Meadowdale Beach area of Edmonds. I would like to address Item No. 5 on page 2 of this letter which states, "discrepancies between the site topographic map and topographic information prepared by the same surveyor for the Spiro residence (across the street, to the east)". Ms. Schluter's topographic map was prepared using the same benchmarks and horizontal control as the other topographic maps that we have prepared in the area. This site was also field inspected by us to make certain that it represents the contours as they exist. I am confident that this map is correct. As for the Spiro residence topographic map, I have checked our files and was unabie to find any record of Group Four ever having prepared a map for this site. Therefore, I think that it must have been prepared by another surveyor. If Landau Associates or the City can produce a copy of the Spiro topography or the name of the surveyor who preformed the work along with the project number associated with the topography, 1 will gladly address the specific discrepancies that were referred to in Landau's letter. SURVEYING ENGINEERING PLANNING MANAGEMENT Thank you for your attention to this matter. If I can be of further assistance or answer any questions that you may have, please don't hesitate to contact me. Sincerely, GRO P`FOUR, INC. an Roupe Vice President Surveying cc: Ursula Schluter DR:ct SURVEYING ENGINEERING PLANNING MANAGEMENT , 8 9 0- 1 9 4 42PEET FILE CITY OF EDMONDS 250 - 5TH AVE. N. . EDMONDS, WA 98020 • (206) 771-0220 • FAX (206) 771-0221 COMMUNITY SERVICES DEPARTMENT Public Works • Planning • Parks and Recreation . Engineering Mailed 4/l/93 March 30, 1993 Ursula Schluter 21701 - 80th Ave. W. #4 Edmonds, WA 98026 Re: Letter dated 3/26/93 - engineering requirements for 15620:.-.75th P1. W. Dear Ms. Schluter, LAURA M. HALL MAYOR Please disregard the portion of the March 26 letter dealing with the sidewalk issue. This letter is to correct the information that was sent to you regarding the sidewalk. Construction of a sidewalk with curbing is required along 75th P1. W., but the option is yours as to whether you wish to contribute or to construct the sidewalk along with your house. If you opt to contribute, the amount of the contribution must be paid by the time the building permit is issued. Should you decide to construct the sidewalk, it must be in place prior to the final engineering inspection on your residence. If you have any questions, please call me at 771-0220, extension 324. Sincerely, ADDISON L. CHRISMAN IV Engineering Inspector ALC/sdt SCHLUTER.3/TXTST530 Alb�_ a Incorporated August 11, 1890 0 gister Cities International — Hekinan, Japan 890-19y V 9"'712 HLE 0 CITY OF EDMONDS 250 - 5TH AVE. N. • EDMONDS, WA 98020 • (206) 771-0220 • FAX (206) 771-0221 COMMUNITY SERVICES DEPARTMENT Public Works • Planning . Parks and Recreation • Engineering March 26, 1993 Ursula Schluter 21701 - 80th Ave. W . , ##4 Edmonds, WA 98026 LAURA M. HALL MAYOR f&,lj4 3 /a(, fi3 Re: Engineering requirements for 15620 - 75th P1. W. Dear Ms. Schluter, Before the Engineering Division can sign off on your building permit application, a site restoration bond must be in place and the sidewalk contribution received. As we tried to explain earlier, the contribution is in lieu of constructing the required sidewalk across your property at the time of construction of your house. With sporadic construction in that area, it is not feasible to construct a small segment of the sidewalk when no other sidewalk has been constructed. In addition, we are not sure which side of the road the sidewalk will be constructed. As far as the street dedication is concerned, we will not require the ten foot dedication as first requested. If you have any questions, please call me at 771-0220, extension 324. Sincerely, ADDISON L. CHRISMAN IV Engineering Inspector ALC/sdt SCHLUTER.2/TXTST530 • Incorporated August 11, 1890 • Sister Cities International — Hekinan, Japan 89p ,9y- irk CITY OF EDMONDS 250 - 5TH AVE. N. • EDMONDS, WA 98020 • (206) 771-0220 • FAX (206) 771-0221 COMMUNITY SERVICES DEPARTMENT Public Works • Planning • Parks and Recreation • Engineering February 11, 1993 Ursula Schluter . 217m j 9o0',ov,- w i¢ Edmonds, WA 4020 fgn;5� LAURA M. HALL MAYOR Mailed 2/11/93 Re: Site restoration bond for 15620 - 75th P1. W., Edmonds Dear Ms. Schluter, Because of the slide potential in the subject area, a site restoration bond will be required. This bond is to cover the repair of damaged utilities and pavement surfaces should a slide occur as a result of constructing a house at the subject address. An estimate of has been determined to cover the total restoration of said utilities and pavement surfaces. In addition to the above requirement, construction of a five (5) foot sidewalk and ten (10) foot street dedication is required. Before a permit can be issued, we must have a recorded document dedicating ten (10) feet of 75th P1. W. to the City of Edmonds. Since development is sporadic in the area, we are not requiring the construction of a sidewalk with the construction of your house. Instead, we will require cash set aside in the amount of $967. If you have any questions, please call me. Sincerely, ADDItON L. CHRISMAN IV Engineering Inspector ALC/sdt c: Sharon Nolan, Permit Coordinator SCHLUTER/TXTST530 Alberts • Incorporated August 11, 1890 • Sister Cities International — Hekinan, Japan 890. 199 .• CITY OF EDMONDS C7 250 - 5TH AVE. N. • EDMONDS, WA 96020 • (206) 771-0220 • FAX (206) 771-0221 COMMUNITY SERVICES DEPARTMENT Public Works . Planning . Parks and Recreation . Engineering G-T FCD� L�tc� LAURA M. HALL MAYOR February 11, 1993 #1j/l�iNG. Ursula Schluter Edmonds, WA 980� Re: Site restoration bond for 15620 — 75th P1. W., Edmonds Dear Ms. Schluter, Because of the slide potential in the subject area, a site restoration bond will be required. This bond is -to cover the repair of damaged utilities and pavement surfaces should a slide occur as a result of ,a constructing a house at the subject address. An estimate of $53,86.7.Fs has been determined to cover the total restoration of said utilities and pavement surfaces. In addition to the above requirement, construction of a five (5) foot sidewalk and ten (10) foot street dedication is required. Before a permit can be issued., we must have a recorded document dedicating ten (10) feet of 75th Pl.-W. to the City of Edmonds. Since development is sporadic in the area, we are not requiring the construction of a sidewalk with the construction of your house. Instead, we will require cash set aside in the amount of $967. If you have any questions, please call me. Sincerely, ADDISON L. CHRISMAN IV Engineering Inspector ALC/sdt c: Sharon Nolan, Permit Coordinator SCHLUTER/TXTST530 a Incorporated August 11, 1890 • Sister Cities International — Hekinan, Japan • �p►R � g �gg3 ENGINEERING March 16th, 1993 City of Edmonds Mr. Addison L. Chrisman IV Engineering Inspector 250 5th Ave N Edmonds Wa 98020 Dear Mr. Chrisman, Thank you for your letter of Feb. llth, recieved March 3rd. In this letter you are requesting a site restoration bond and funds for construction of a sidewalk in the future, plus a 10' dedication of my land to the City. Since the City and consultants require so many changes, my building funds are being depleated rapidly, as such it is not sure wether it is financially possible for me to go ahead with the project. Once the permit is to be issued, I will know if it is still possible for me to go ahead. At that time I will be more than agreeable to adhere to your requests. Hoping you under- stand, that ,unless I am able to build, I can not afford to make such a generous gift. However, I fully hope to be able to build a home. Sincerely, Ursula Schluter c: Mayor Laura Hall LANDAU AASSOCIATES, INC. Environmental and Geotechnical Services City of Edmonds 250 5th Avenue North Edmonds, WA 98020 u J Attn: Ms. Jeannine L. Graf BUILDING MAR 121993 March 11, 1993 RE: PRELIMINARY GEOTECHNICAL REVIEW PROPOSED SCHLUTER RESIDENCE LOTS 1 AND 2, BLOCK 28 OF THE PLAT OF MEADOWDALE BEACH 15620 75TH PLACE WEST MEADOWDALE AREA EDMONDS, WASHINGTON In accordance with your request, we have completed a preliminary geotechnical review of plans and other submitted documents concerning the above -noted proposed residence. Our review was conducted using City Ordinance No. 2661 and the UBC as the standard for comparison. A list of the submitted documents we reviewed is included as Attachment 1. As part of our review, we also referred to geotechnical studies prepared for recent nearby residential projects for which we have provided similar review services. These documents contain information useful in developing a broader understanding of soil and groundwater conditions in the immediate vicinity of the project site. A list of referenced documents is included as Attachment 2. According to information provided in the submittal, the site is located within the Meadowdale landslide area approximately 270 to 360 ft north of the intersection of 75th Place West and 158th Street S.W., and between 75th Place West and the Burlington Northern railroad tracks. This location places the site within an arcuate depression suggestive of a localized slide area within the overall Meadowdale landslide area. According to studies performed for the City of Edmonds this property may have been involved in landslide movement in 1955-1956, and again in 1973-1974. Our review of submitted documents for this project indicates that there are several omissions, inconsistencies, and possible inaccuracies in the submittal package. Examples of these include: 1) omission from the design and plans of several recommendations provided by Shannon & Wilson in their 1990 report, including up -and -down -slope grade beams and details of the trench drain; 2) inaccurate declarations in the Environmental Checklist to the effect that P.O. BOX 1029 • EDMONDS, WA 98020-9129 • (206) 778-0907 • FAX (206) 778-6409 SPOKANE: (509) 327-9737 • FAX (509) 327-9691 / TACOMA: (206) 926-2493 • FAX (206) 926-2531 none of the site will be covered by impervious surfaces, and that no filling and grading will be accomplished; 3) absence of calculations in support of the proposed storm drainage system; 4) no review of the environmental checklist by the project geotechnical consultant; 5) discrepancies between the site topographic map and topographic information prepared by the same surveyors for the Spiro residence (across the street, to the East); 6) no clear identification of the lead design professional; and 7) absence of soil pressure distribution diagrams and design criteria for pile lateral resistances. We are also concerned that elements of the proposed project are based, to a large degree, on assumed subsurface soil and groundwater conditions. The geotechnical recommendations provided to date have been based on subsurface information from test pit explorations described in the 1986 Earth Sciences report. If our understanding of the site location is correct, only Test Pits 2 and 3 were excavated within the property and are, therefore, strictly relevant to the project (Test Pits 1 and 4 are located between the site and the Jewell property to the south). In addition, use of the 1986 Earth Sciences report was limited to the owners of the site at that time; the author specifically excluded future owners from using the report. Foundation recommendations provided in the 1990 Shannon & Wilson report appear to be based on the assumption that Test Pit 2 penetrated through the slide debris blanketing the site and encountered hard undisturbed silt. In our opinion the soil log of Test Pit 2 does not clearly support that assumption. The contact between the slide debris and the underlying hard silt likely varies in elevation across the site and could be several feet deeper in the building area than the maximum depth assumed by Shannon & Wilson. Based on a geologic cross section prepared by Landau Associations, this contact could be in the range of 20 to 30 ft deep within the proposed building area. Shannon & Wilson should comment on their interpretation of the available information and the validity of applying the 1986 Earth Sciences report to the current project. Earth Sciences in their 1986 report, and Shannon & Wilson in their 1992 Plan Review and 1993 Geotechnical Declaration Letter, appear willing to accept that the slide potential for the site has been reduced to an acceptable level of risk. The reduced level of risk appears to be based on the overall reclassification of slide potential within the Meadowdale landslide area by GeoEngineers, Inc. in February 1985. That reclassification was based on an overall lowering of groundwater levels within the Meadowdale area subsequent to the installment of drainage improvements by the City. However, GeoEngineers also noted that the slide potential on individual sites within the Meadowdale area could remain high despite the overall benefits of 2 LANDAU ASSOCIATES, INC. the drainage improvements. Where groundwater is still at or very near the ground surface, it is probable that the risk of movement is still as high as it was prior to the City improvements (i.e., 90 percent probability of movement within a 25-year period rather than 30 percent probability as noted on the most current City map). Groundwater seepage on the site was noted in both the 1986 Earth Sciences and the 1990 Shannon & Wilson reports, as well as in the 1985 Geologic Services report related to the nearby Jewell property. However, because actual groundwater levels at the site have not been well documented it does not appear possible to accurately assess the topic of landslide risk. For this reason, we strongly recommend that the design professionals involved in this project consider the installation of piezometers for assessment of existing groundwater and related slope conditions. The City should request the statistical probability for landslide movement for the site based on that assessment. Construction of augercast piles and trench drains will likely require construction of temporary access to portions of the site, and generate excess spoil material. These activities could include temporary cut and fill slopes, side -cast fills, and large temporary stockpiles of .QMWA64, excavated soil. The submittal documents, including the 1990 Shannon & Wilson report (and fg"& - their 1992 Plan Review), do not address construction methods or their consequences. We recommend that the design professionals review the plans and recommendations, and comment on construction -related issues including (but not limited to): 1) site access, 2) temporary cut and fill slopes; 3) spoil stockpiling and removal; 4) temporary erosion and sediment control measures; 5) site investigation; 6) construction shoring; and 7) short- and long-term effect of site grading activities on site stability. We recommend that the plans and other submitted documents be returned to the applicant for action. A lead design professional should be designated, and that person should review the documents and make, or request from other design professionals, whatever appropriate changes are necessary in order to be consistent with the requirements of Ordinance 2661, and recommendations provided in the geotechnical reports. In addition, the Geotechnical Engineer should evaluate and comment on specific issues raised herein. We would be pleased to discuss with the design professionals the issues noted above, as well as items which we have not listed. Please note that Landau Associates did not review structural calculations. 9 LANDAU ASSOCIATES, INC. 0 1 0 Please call if you have questions concerning this review, or require the services of Landau Associates for subsequent review services. WDE/TAH/nlb No. 74-21.10 03/11/93 JAEDMONMSCHLUTER.LTR 3 copies submitted Attachments Very truly yours, LANDAU ASSOCIATES, INC. By: W, William D. Evans, CPG Project Manager and 1"01644- Wade Gilbert, PE Project Engineer 4 LANDAU ASSOCIATES, INC. • • ATTACHMENT 1 • Sheets VP, T, Al through A5, and Sl through S3 of Plans for New Residence for Ursula Schluter, Philip L. Brown, Architect, dated January 26, 1993. • Environmental Checklist, submitted to the City by Ursula Schluter, dated January 26, 1993. • Soil Conditions, Earth Sciences, March 21, 1986. • Geotechnical Report, Proposed Residence at Lots 1 & 2, 75th Place West, Shannon & Wilson, Inc., dated March 29, 1990. • Plan Review for Proposed Residence 15620 75th Place West, Shannon & Wilson, Inc., dated July 17, 1992. • Geotechnical Declaration and Statement of Risk, Proposed Residence 15620 75th Place West, Shannon & Wilson, Inc., dated January 29, 1993. • Landslide Acknowledgement Declaration, Ursula Schluter, dated december 23, 1992. • Covenant of Notification and Indemnification/Hold Harmless, Ursula Schluter, date January 26, 1993. • Affidavit of Meadowdale Landslide Permit Posting, Ursula Schluter, dated January 26, 1993. 03/11 /93 1:\EDM0NDS\SCHLUTER.LTR LANDAU ASSOCIATES, I;\C. ATTACHMENT 2 • Site Geotechnical Study (for Jewell Property), Geological Services, Inc., dated June 6, 1985. • Site Geotechnical Study (for Riggle Property), Geological Services, Inc., dated April 23, 1985. • Geotechnical Engineering for the Proposed Spiro Residence, Hemphill Consulting Engineers, dated December 10, 1990. • Geotechnical Engineering Study (for Chynoweth Property), report by Terra Associates, Inc., dated July 28, 1990. 03/11 / 93 I: \ EDMON DS \SCHLUTER.LTR LANDAU ASSOCIATES, INC. /5bZ0 7 PL t? krif �,y OL . ENGINEERS COST ESTIMATE 'D�fti 2 ITEM. DESCRIPTION OF WORK UNIT ySUR QTy Ufm COST TOTAL //O X .50 Sy ,...::o 'f0 /O�JOO z ?aa /400 %C�t✓nrs�ll j'*,Cot z' 43 f.4 Z 3oa lcf�c .btts.! S�c"..�sr�-.1: e t— Iola .cv t. mac✓ �! J f /5 .6 Colo /Ao X L z I -All 3 3 I/v . /S / 7 .33117 Allk Pmvlrr APPLICATION REQUMEMENTS TO: Permit Coordinator, Building Division FROM: Lyle Chrisman, Engineering Inspector OWNER sue/ % �= PLAN CK # ADDRESS: /S 6 Z� 7S �'G DATE: 4 —� 93 After review of the subject permit application, the following requirements mustbe met. I. Construction hours are: WEEKDAYS .......... 7:00 A.M.-10:00 P.M. WEEKENDSMOLIDAYS..... 10:00 A.M.-6:00 P.M. 2. A separate RIGHT-OF-WAY- Construction Permit is required for all work on Publicproperty. (ECDC 18.60) 3. Truck haul route plan must be submitted and approved prior to permit issuance. 4. Builder/Owner is responsible for containing all temporary runoff and erosion control on site. (ECDC 18.30.030d) S. NO WORK SHALL BE DONE W MINIS FEET OF STREAMS OR 10 FEET FROMANY CLOSED DRAINAGE FACIL. ITT. BUILDEWOWNER IS REPSONSIBLU FOR IDENTIFYING CONDTIIONS ON THE DRAWING. (ECDC 18.30.50G) 6. FILTER FABRIC FENCE SHALL BE INSTALLED AND INSPECTED PRIOR TO CLEARING AND CONSTRUCTION. (ECDC 18.30) 7. INSPECTIONS ARE REQUIRED ON STORM DRAINAGE SYSTEMS, TIGHTLINF.S, FOUNDATION DRAINS, AND CATCH BASIN INSTALLATION. INSPECTIONS ARE REQUIRED PRIOR TO BACIUMLING. (ECDC 18.30) 8. Repair or replace all defective existing curb, gutter, and sidewalk adjacent to the property. If an intersection is involved a handicap ramp may be required. Contractor shall meet with the City Engineering Staff to determine the extent of repair prior to issuance of the permit. (ECDC 18.90) 9. Driveway slope shall not exceed 14 % without a waiver. Every attempt should be made to keep the slope below 14 40. Waiver granted to __%. (ECDC 18.80.060D) 10. Drivewayi must be paved from property line to City RIGHT-017-WAY. A separate perimit is required. (ECDC 18.80.060C) 11. INSPECTIONS ARE REQUIRED ON DRIVEWAYS AND SIDEWALKS PRIOR TO AND AFTER POURING. (ECDC 18.30) 12. No burning of construction refuse without a permit from the Fire Department. 13. Connection to City water system is required. There is a separate charge for the water meter. (ECDC 7.30) 14. Aback water valve is required if downstairs plumbing is below the elevation of upstream manhole. (ECDC 7.20) 15. Water and sewer main lines should be separated by 10 feet minimum. (ECDC 18.10) 16. Connection to the City sanitary system is required. A ieparate permit.is required. LID// Z/e Fees paid: Yes No Charge _ (ECDC 18.10) 17. Underground wiring is required on all new construction; and for additions, alterations, and repairs that exceed 50 % of the total assessed value of the structure. (ECDC 18.05.010) .18. A FINAL ENGINEERING INSPECTION IS REQUIRED PRIOR TO THE BUILDING DIVISION GRANTING OCCU- PANCY OF THE BUILDING OR STRVCTURF,. ' (ECDC 18.90) 19. Sl �Btirl� ,Pry pit, ihtsr�� •- — TR __L IRV .CF.IVED JANI 61993 &-4 /0 -r �LO 7- �41C) OJECT REVIEW CHECKLIST CHZ—C-t--F�� PLAN CHECK PROJECT ADDRESS: RECEIPT DATE: . .................. ........... ............ ........... ...... .. ..... ....... .. .. ... ........... ...... ..................... X ............ .......... ........ .................. .... ... . .. ... . ... . ... . .. .......... ... ... X. ........ �iii!iiiii.i!! ............... X . ........ L'A WATER..:.;:.;::, ....... .. ........ . ..... .. .......... m FIR BL EWER:: TREE, Setbacks/Variance/Setback Adjustment 1M.-M gg mggg--�� x Conditional Use Permit ADB Requirements Other Zoning Requirements Underground Wiring Required - - - - - - - - - - - - - - - - - - - - - - ........... . ..... .. Lot Slope 15% M§ SEPA Environmental Checklist/Hydraulics Permit ...... ..... Tree Cutting Plan Plat/Subdivision Requirements IM . . . . . . . . . . . . . ...... Legal Description Verification Quit Claim/Street (pVd—ication -A-) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AX Easements - Public/Private Engineering Storm Drain Review Fee ----- --------- '00 -A 11: Engineering 2.2 Inspection Fee X . . . . . . . . . . . . Drainage Plan (On -Site) ----- - ......... . Setback - To of Bank, Stream, Water Courses Setback - Storm Drain Line Open Ditch - Existing ... .. Culvert Required — ---- ---- ---- Culvert Size Shoulder Drainage/Shale Open Runoff N Catch Basin Required Driveway Slope & Vehicle Access . . . . . . . . . Sidewalk Required 4 116 - - - - - - - - - - - - - - - - - - - - --------------- ------------- Curb & Gutter Required . . . . . . . . . . . . ; . X. Curb Cut For Driveway Required Street Paving Required Right -Of -Way Construction Permit Required Y!55; Street Name Sign Required29 ....... . . . . . . X.. Other Signing Required X., Bond Required For Public Improvements FEMA Map Check/Water Table MEN. M ' X: Side Sewer Availability jeolo Calculate Sewer Connection Fee If No LID X., Create Street File ...... Existing Water Main Size Water Meter Size . . . . . . . . . . . . . . Service Line Size Water Meter Charge Required -7.50*0 X. Hydrant Required Hydrant Size Existing Fire Line Charge Required - Sprinkler Street Cut 71 ... ... ..... Miscellaneous 3wo /Wzaor, •.......... • . . . . . . . . . . - ------- W-X 4 Reviewed By: Q n ro FIRE PLANNING 0 I El "".1*ERING. PUBLIC WORKS r _ SFMNON SEATTLE 6WILSON, INC. GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS KEVERETT EN EWICK FAIRBANKS ANCHORAGE SAINT LOUIS January 29, 1993 Ms. Ursula Schluter 2701 80th Avenue West, #4 Edmonds, Washington 98020 RE: GEOTECHNICAL DECLARATION AND STATEMENT OF RISK, PROPOSED RESIDENCE AT 15620 75TH PLACE WEST, EDMONDS, WASHINGTON Dear Ms. Schluter: We have reviewed the plans for the proposed residence at 15620 75th Place West in Edmonds, Washington, and our comments were presented in a letter dated July 17, 1992. I our opinion, the plans and specifications conform to the recommendations in our geotechnical report. In our opinion, the risk of damage to the proposed development or to adjacent properties from soil instability will be minimal, subject to the conditions set forth in the report. As a result of the drains to be installed, the proposed development will result in a net increase in stability of the site; therefore, the proposed development will not increase the potential for soil movement. There is no way to accurately determine the statistical probability of earth movement; however, once the proposed development is completed in accordance with our recommendations, we . believe the risk of significant earth movement at the site will be very small. We appreciate the opportunity to be of service. Sincerely, SHANNON & WILSON, INC. EXPIRES 7/25/ 9► -5 Ralph N. Boirum, P.E. Senior Associate RNB/jnd W5385-02.LTR/W5385-02-1kd/jnd 400 NORTH 34TH STREET -SUITE 100W-5385-02 P.O. BOX 300303 Z-1 SEATTLE, WASHINGTON 98103 206.632.8020 FAX 206.633.6777 Ms. Ursula Schluter VANNON 6WILSON. INC. ' January 26, 1994 Page 5 shown in Figure 1. Subdrains would consist of a 6-inch (minimum) diameter slotted plastic ' pipe bedded in 3/8-inch pea gravel in the bottom of a sand -filled trench. The location of the trench subdrain will depend on design of the house, and should be determined after the layout of the house has been established in the field. ' We recommend that no additional fill be placed on the site, as the additional weight could ' reduce the stability of the site. Much of the soil excavated from trench subdrains should be removed form the site, although some may be used as backfill in the upper 4 or 5 feet of the trench. We should review any plans for placement of fill on this site so that unstable tconditions are not created. ' It is our opinion that the proposed structure, supported on augercast concrete piles, will not experience significant lateral deflections or settlement. With regard to utility connections, we do not foresee the need for flexible utility connections for the proposed structure. Site Sta ility tThe results of our studies indicate that the property can be developed and the proposed residence constructed in such a way as to increase the stability of the site. We expect that construction of a trench drain across the property will lower the ground water level and increase the stability of the site. In our opinion, once this site is developed in accordance with our recommendations, the probability of substantial loss due to future sliding will be less than 30 percent in a 25-year period. Excavation for the recommended trench subdrain will result in an increased possibility of local sliding in the immediate vicinity of the trench. This risk of sliding would be limited to within about 30 feet of the excavation and would not endanger the street or neighboring properties. The use of a trench box and immediately backfilling the completed trench to minimize the length of excavation open at any one time will minimize the potential for sliding during construction. Completed portions of the trench will immediately begin to drain the site, and the stability of the site should increase as the work proceeds. Concrete Piles Augercast piles are installed by rotating a continuous -flight hollow -stem auger to a pre- determined depth. When the depth is reached, a high strength sand -cement grout is pumped, W-5385-02 W-5385-02 7 - SHANNON & WILSON, INC. Over Geotechnical & Environmental Consultants 38 Yea rs of Excellence 400 North 34th Street, Suite 100 - P.O. Box 300303 - Seattle, WA 98103 - (206) 632-8020 - Fax: (206) 633-6777 July 17, 1992 Ms. Ursula Schluter 21701 80th Avenue West #4 Edmonds, Washington 98020 RE: PLAN REVIEW FOR PROPOSED RESIDENCE 15620 75TH PLACE WEST, EDMONDS WASHINGTON Dear Ms. Schluter: This letter presents the results of our plan review for the proposed construction of a single-family residence at the above property. The property is identified as Lots 1 and 2 of Meadowdale Beach area in Edmonds. Our review of the project is based on the set of drawings provided to us by Ms. Ursula Schluter, and on our previous geotechnical studies for the project; refer to our geotechnical report dated March 29, 1990. CONCLUSIONS AND RECOMMENDATIONS In our judgement, with respect to overall slope stability considerations, the plans in general conform to the recommendations in our March 29, 1990 geotechnical report. The risk of damage to the proposed development from soil instability will be minimal, in our opinion, subject to conditions set forth in the geotechnical report; and the proposed development will not increase the potential for soil movement, nor increase the risk of instability for adjacent properties if our recommendations are followed. Installation of the proposed trench subdrain should result in an increase in the stability of the site. It should be noted that the geotechnical report presents recommendations regarding some soils - related aspects for the project which are not specifically shown on the plans. This includes recommendations regarding installation of augercast piles, and surface and subsurface drainage measures including the trench subdrain installation. It is recommended that the geotechnical Seattle e Everett - Kennewick e Fairbanks - Anchorage - St. Louis PRESIDENT: Earl A. Sibley, P.E. SR. VICE PRESIDENT: Atef A. Azzam; Raymond P. Miller, P.E.; Harvey W. Parker, P.E.; George Yamane, P.E. VICE PRESIDENT: Herman H. (Tex) Druebert, P.E.: Richard H. Gates, P.E.; W. Paul Grant, P.E.; Leland B. Jones, P.E.; Thomas E. Kirkland, P.E.; Dexter N. McCulloch, C.E.G.; Gerry Millar, R.G.; Frank W. Pita, P.E., P.G.; MingJiun (Jim) Wu, P.E. CONSULTANT: William L. Shannon, P.E. Ms. Ursula Schluter W-5385-02 July 17, 1992 Page 2 report be referenced on the plans and/or contract documents, so that our recommendations can be followed as appropriate. Further, it is recommended that the typical trench subdrain detail from our geotechnical report (Figure 2) be shown on the drawings. The drawings indicate approximate locations of two trench subdrains extending approximately north -south across the property. In our opinion, depending upon soil and groundwater conditions encountered during test pit excavation at the start of construction, it may be appropriate to install only one trench subdrain. The trench subdrain should be field -located by us based on several test pits excavated on the site immediately prior to subdrain installation. The plans indicate that 24-inch diameter augercast piles will be installed with a minimum penetration of 16 feet into the firm native soil. The pile size and penetration are greater than that recommended in our report of March 29, 1990, but are acceptable. In our opinion, the proposed piles should be capable of developing an allowable capacity of at least 20 tons. We recommend that the proposed pile locations and approximate pile lengths at each location be indicated on the site plan. The actual lengths, however, should be determined in the field by a geotechnical engineer, based on soil conditions encountered during drilling. If you or your representatives have any questions, please call. We look forward to assisting you with geotechnical construction monitoring for this project. Sincerely, SHANNON & WILSON, INC. Sandeep Puri Engineer SP:RNB:TEK/sp W5385-02.L7*R/SP-tkd/dgw l4Z Ralph Boirum, P.E. Senior Associate SHANNON & WILSON. INC. 8 T H ET RL,_ N *44t ke /- A, H,�VE !-f.s4n n4r C--oTe6HO16Au 12�Pdr2-T oN E-PMON651WA i,!7,q5HAHNo�1 4 W(LSOO QA-r,0 MA" 2191 l'llo- Z i-IAVI✓ At,'50 STUOIF,-O T-0P06R-APH16A1-Su0,Vr--'{ t U N v e2-S'T4H0 u HE `fQt.�v � �co �°ol +'T � f-i~ Po YLf f T H 5 S -0- i`� --}{F wi i �J TH F_ 9 - IG.N fW&� b, Z. At� RECEIVED J A N i 6 '6 33 ' ---- PERMIT COUNTER 6:T 13 V F • LANDSLIDE ACKNOWLEDGEMENT DECLARATION: I, Ursula Schluter, the undersigned and property owner of Lot 1 and 2, block 28 Medowdale Beach 15620 75th Pl. W Edmonds Wa 98026 a) Accept the risk of developing in an area with potential unstable soils and will advise , in writing, any prospective purchasers of the site, or any prospe 've lessees of structures or portions of a-'riticture on t site of the slide potential of the are.. b) That the accuracy of all permit submittal information is warranted by me,and relieves the City and its staff from any liability associated with reliance on such permit application submittals.All conclusions shall be those of TIrsula SChluter/owner and my design professionals. Owner/Applicant: Subscribed and sworn to before me on this a3day of Deaq, gr 1992 N! Wyk %Rj� 1 c i n E, IVA , OF 00 / i a OF WAS`\ an d for the State of Washington 0- � 6, ex J7— 6 y _.. A • f Edm City o ons RIGHT-OF-WAY CONSTRUCTION PERMIT Permit Number. l" Uwe Date: � - A. Address or Vicinity of Construction: 15620 75th Pl 'r; GTE top ace, opera e, an ma ntaW a I)uried serviue 18 of B. Type of Work (be specific): wi ra from existing term #725 located at 15631 75th P1 9 0 1 9 Then west, o a usidence at 15620 75th P1 W. GT o plow 10 Sfe t nd push one road 1 fee r7.' . footage lee . Mary A Sower, Permit Coord. C. Contractor: GTE Northwest INcor prated Contact: Dennis Alexander 771-9036 or mobile 388-1353 22113 20th Av S , Suite 130 Mailing Address: i wa gsn91 Phone: r.tary 9n 488-109 State License #: Liability Insurance: Bond: $ D. Building Permit # (if applicable): Side Sewer Permit # (if applicable): E. ❑ Commercial ❑ Subdivision ❑ City Project ® Utility (PUD GTE) WNG, CABLE, WATER) ❑ Multi -Family Q Single Family ❑ Other 2850-9PO01llf3 242310 INSPECTOR: INSPECTOR: W F. Pavement or Concrete Cut : ❑ Yes UNo G. Size of Cut: x H. Charge $ Please see attached sketch. APPLICANT TO READ AND�$IGN INDEMNITY: Applicant understands and by his signature to this application, agrees to hold the City of Edmonds harmless from injuries, damages, or claims of any kind or description whatsoever, foreseen or unforeseen, that may be made against the City of Edmonds, or any of its departments or employees, including or not limited to the defense of any legal proceedings including defense coats, and attorney fees by reason of granting this permit. THE CONTRACTOR IS RESPONSIBLE FOR WORKMANSHIP AND MATERIALS FOR A PERIOD OF ONE YEAR FOLLOWING THE FINAL INSPECTION AND ACCEPTANCE OF THE WORK. ESTIMATED RESTORATION FEES RILL BE HELD UNTIL THE FINAL STREET PATCH IS COMPLETED BY CITY FORCES, AT WHICH TIME A DEBIT OR CREDIT WILL BE PROCESSED FOR ISSUANCE TO THE APPLICANT. Construction drawing of proposed work required with permit application. A 24 hour notice is required for inspection; Please call the Engineering Division, 771-0220. Work and material is to be inspected during progress and at completion. Restoration is to be in accordance with City Codes. Street shall be kept clean at all times. Traffic Control and Public Safety shall be in accordance with City regulations as required by the City Engineer. All street cut ditches shall be patched with asphalt or City approved material prior to the end of the working day; NO EXCEPTIONS. I have read the above stat ent stand the permit requirements and the pink copy of the permit will be available on site at all 9 p ^pollp" s. Signature: , QtawArt John H. Stewart Date: November 29, 1995 (Contractor or Agent) Uprns Supv-OSP Engrg. CALL DIAL -A -DIG PRIOR TO BEGINNING WORK FOR CITY USE ONLY APPROVED BY: ��J�►' RIGHT OF WAY DEPOSIT TIME AUTHORIZED: VOID AFTER I K t`At2 DAYS SPECIAL CONDITIONS: NO A (' ? / .,yrs AL---Owtt? I N RUAOWAY. COMMENTS: DISRUPTION FEE/FUND 111: RESTORATION FEE: PERMIT FEE: TOTAL FEE: RECEIPT FEE:_ ISSUED BY: =' W NO WORK SHALL BEGIN PRIOR TO PERMIT ISSUANCE Eng. Div. 1994 FIELD INSPECTION NOTES Comments Diagram CONTRACTOR CALLED FOR INSPECTION Partial Work Inspection by P.W.: Work Disapproved By: FINAL APPROVAL BY: (Fund 111 - Route copy to Street Dept.) ❑ YES Date: Date: ❑ NO Im 11/29/95 02:50 • �I Wol Jin T z Sao ®Owe z or d�z tnWJW In x P cr O LLI O MC - 0-,1dW W0056u aaoco_5 m 0 W 03 W = I.- In 0 W CL tar N, N0. 141 903 v� F- u !� 8 y 0 I C)9 City of Edmond RIGHT-OF-WAY CONSTRUCTION PERMIT Permit Number. �� Issue Date: A. Address or Vicinity of Construction: Ac) :z` 7;'1 B. Type of Work (be specific):" Q.C,QU- L 1 " C 1 l , e l i-J C. Contractor: SKUVQ1 S1-i CG1.1 A T,' P - Q • 0 - Contact: f\ C�e I-) Mailing Address: )11\()\b Wa`i Cis Phone: (t iCJ" 310 State License #: i 96C c� ,�o Liability Insurance: Bond: $ D. Building Permit # (if applicable): Side Sewer Permit # (if applicable): E. ❑ Commercial ❑ Subdivision ❑ City Project [..,Utility (PUD, GTE, WNG, CABLE, WATER) ❑ Multi -Family lll`° Single Family ❑ Other INSPECTOR: f' INSPECTOR: F. Pavement or Concrete Cut : U Yes Wo G. Size of Cut: x H. Charge $ APPLICANT TO READ AND SIGN INDEMNITY: Applicant understands and by his signature to this application, agrees to hold the City of Edmonds harmless from injuries, damages, or claims of any kind or description whatsoever, foreseen or unforeseen, that may be made against the City of Edmonds, or any of its departments or employees, including or not limited to the defense of any legal proceedings including defense coats, and attorney fees by reason of granting this permit. THE CONTRACTOR IS RESPONSIBLE FOR WORKMANSHIP AND MATERIALS FOR A PERIOD OF ONE YEAR FOLLOWING THE FINAL INSPECTION AND ACCEPTANCE OF THE WORK. ESTIMATED RESTORATION FEES WILL BE HELD UNTIL THE FINAL STREET PATCH IS COMPLETED BY CITY FORCES, AT WHICH TIMEA DEBIT OR CREDIT WILL BE PROCESSED FOR ISSUANCE TO THE APPLICANT. Construction drawing of proposed work required with permit application. A 24 hour notice is required for inspection; Please call the Engineering Division, 771-0220. Work and material is to be inspected during progress and at completion. Restoration is to be in accordance with City Codes. Street shall be kept clean at all times. Traffic Control and Public Safety shall be in accordance with City regulations as required by the City Engineer. All street cut ditches shall be patched with asphalt or City approved material prior to the end of the working day; NO EXCEPTIONS. I have read the above statements and understand the permit requirements and the pink copy of the permit will be available on-&te at ti s for ins ec 'on purposes. Signature: Date: V (Contractor r Agent) CALL DIAL -A -DIG PRIOR TO BEGINNING WORK FOR CITY USE ONLY APPROVED BY: RIGHT OF WAY DEPOSIT _ TIME AUTHORIZED: VOID AFTER !!fU DAYS DISRUPTION FEE/FUND Ill: SPECIAL CONDITIONS: COMMENTS: RESTORATION FEE: PERMIT FEE: TOTAL FEE RECEIPT FEE: DATE: ISSUED BY: NO WORK SHALL BEGIN PRIOR TO PERMIT ISSUANCE Engrg. Div. 1991 KI 0 JI Z! I D ou ICE0 .0 o E (-6 DWI C, � a ' a < z ow o z 0 < z 0 m z z ' 0 > z z W dt __j H5 & L o u z O z zN o Y. z< u o < c o D. c,� < o I -- MR Mq-w,% 0 Cit of Edmonp y RIGHT-OF-WAY CONSTRUCTION PERMIT Permit Number: �tJ, Issue Date: Z:;� --/(,;, A. Address or Vicinity of Construction: 1 5f.9t1 75 pl qu (9608023) B. Type of Work (be specific): Install Service C. Contractor: Washington Natural. Gas Mailing Address: 1 179 75 St gw FyAprntt State License li: 98203 D. Building Permit Al (if applicable): Contact: Hariamne Kingsbury Phone: 3Sfi-7SQn Pert 7596 Liability Insurance: Bond: $ Side Sewer Permit # (if applicable): E. ❑ Commercial ❑ Subdivision ❑ City Project Q Utility (PUD, GTE, WNG, CABLE, WATER) ❑ Multi -Family ❑ Single Family ❑ Other INSPECTOR: INSPECTOR: L,,3kA c.,A F. Pavement or Concrete Cut : ❑ Yes QNo G. Size of Cut: x H. Charge APPLICANT TO READ AND-iIGN INDEMNITY: Applicant understands and by his signature to this application, agrees to hold thg City of Edmonds harmless from injuries, damages, or claims of any kind or description whatsoever, foreseen or unforeseen, that may be made against the City of Edmonds, or any of its departments or employees, including or not limited to the defense of any legal proceedings including defense costs, and attorney fees by reason of granting this permit. THE CONTRACTOR IS RESPONSIBLE FOR WORKMANSHIP AND MATERIALS FOR A PERIOD OF ONE YEAR FOLLOWING THE FINAL INSPECTION AND ACCEPTANCE OF THE WORK. ESTIMATED RESTORATION FEES WILL BE HELD UNTIL THE FINAL STREET PATCH IS COMPLETED BY CITY FORCES, AT WHICH TIME A DEBIT OR CREDIT WILL BE PROCESSED FOR ISSUANCE TO THE APPLICANT. Construction drawing of proposed work required with permit application. A 24 hour notice is required for inspection; Please call the Engineering Division, 771-0220. Work and material is to be inspected during progress and at completion. Restoration is to be in accordance with City Codes. Street shall be kept clean at all times. Traffic Control and Public Safety shall be in accordance with City regulations as required by the City Engineer. All street cut ditches shall be patched with asphalt or City approved material prior to the end of the working day; NO EXCEPTIONS. I have read the above statements and understand the permit requirements and the pink copy of the permit will be available on site at all times for inspection purposes. Signature: Date: n2-12-96 ontract or ent CALL DIAL -A -DIG PRIOR TO BEGINNING WORK FOR CITY USE ONLY APPROVED BY: 1,1i� +�+ RIGHT OF WAY DEPOSIT TIME AUTHORIZED: VOID AFTER t `i IFA "DAYS SPECIAL CONDITIONS: !f� n� ✓� l�P jp COMMENTS: DISRUPTION FEE/FUND Ill: RESTORATION FEE.: TOTAL FEE: � p DATE:. ISSUED BY: NO WORK SHALL BEGIN PRIOR TO PERMIT ISSUANCE Eng. Div. 1994 • FIELD INSPECTION NOTES Comments• Diaaram (Fund 111 - Route copy to Street Dept.) CONTRACTOR CALLED FOR INSPECTION ❑ YES Partial Work Inspection by P.W.: Work Disapproved By: Date: FINAL APPROVAL BY: Date: ❑ NO Watermain depth gas main CIN Addendum to: City of Edmonds Right of Way Permit Application Submitted by: Marianne Kingsbury Engineering Aide Washington Natural Gas 135,6-7500 . X7596 ' Jos 9�0�23 15eo2.0 �5 Ply Sw vT SWI Key: -W- Water -G- Gas -SS- Sever .e. Wa�ter hydrant 0 Water valve Washington Natural Gas Company 1122 75th Street S.W., Everett, Washington 98203, (206) 355-3331 • Natural GAS AWhftrylon Energy GorrrxrN 2 Addendum to: City of Edmonds Right of Way Permit Application Submitted by: Marianne Kingsbury Engineering Aide Washington Natural Gas 13516-7500 .X7596 Job q�o�23 15�20 �5 Ply SW Key: Watermain depth -W- Water-G- Gas -SS- Sever " gas main $ Water hydrant p Water valve Washington Natural Gas Company 1122 75th Street S.W., Everett, Washington 98203, (206) 355-3331 .`�../�� /�(�f/��)l'/♦�fW��jfN/• I�jf - s /'�r�'\I�'pp CITY OF EDMONDS USE PERMIT ZONE `c NUMBER��-C CONSTRUCTION PERMIT APPLICATION M11 OWNER NAME OF BUSINESS JOB y=,;= . SUITE/APT N J J) ADDRESS f C_ � � /').-.:�L,. �ri�/�r'SUL y.%�„ UT= A;� LEGAL DESCRIPTION CHECK SUBDIVISION NO. LID NO, " MAILING ADDRESS '7� �,/f y}^/�'yt'-/ O '.fir f 7V i) f �!�, '� (" "ri + 1 ' PUBLIC RIGHJ7 OF WAY PER OFFICIAL STREET MAP, TEESCP Approved ❑ CITY ZIP TELEPHONE NUMBER ( RW Permit Required j 1 ,r/ ,[ �) (' �y } ^,{�'J"!(.-'f f� �` .f r; (✓" r '..1,% EXISTING REQUIRED DEDICATION 1 Street Use Permit Req'd ❑ l'Fli..^ ��5//V(�gr ' r/.✓/.^ .,fyysy^"c='`�:� PROPOSED W " `- inspection R Required NAME �l �, �•, (J Sidewalk Required ❑ O REMARKS W w A DR�ES�StM/1(�/77If�d IfJ��f", };•�(�'{..� 2 q CITY ZIP TELEPHONE NUMBER,,_}-.(`� Rvxyfy'' I — �'7 Ok'iaJAi-1 TD GcrVFT"Ru[}'L YJ :.. R ry y,,la. ,+i�cr NAM' Blodgett Construction _ �� - ' �� Q. t.� Associates Inc. ENGINEERING MEMO DATED p / jr REVIEW BY i ADDRI 1051 Westview Drive /a�f` / r-'- 0 .,. Wenatchee, WA 98801 RF.. METE IZE " BWOIN PPLY SIZE 7"7 �i F U _ __. _ REMARKS/ — a 3 STATE LII:tNLI NI:",r�=� F_%PIP:1T!GN GATE IL/ /'— SIGN AREA SEPA REVIEW ADB Legal DE`SCrlptlOn Of Property - include all easements �.f ALLOWED PROPOSED COTE( EXEMPT SHORELINE-N.' •"r VARIANCE OR Cu PtAN ING REVIEW BYIf w V1SAV4' 16 "19Y = 1�tf.YJ/f' i SACK"S — FEET �. H`iLr-i•GHH T^' LOT COVERA E l I w. TProperty 510E AR Tax Account — REMARKS ) a. ✓t tfG' Parcel No. MNEW jt��xj� L.L-:1 RESIDENTIAL PLUMBING ADDITION � COMMERCIAL ® MECHANICAL gEMODEL APT. SLOG. SIGN _ .j- � ) 2 f '`4t • _may ,- 11,Y�I G DIN FENCE REPAIR 4: ]I !..�� CYDS El (_x_FT) O ECKEDgg�y(� TYPE OF CONSTRUCTION CODE�''"1J HEIGHT O WOODSTOVE ElHOTGROUP SWIM POOL DEMOLISH INSERT HOT TUB/SPA SPECIAL INSPECTOR _ AREA OCCUPAN f. �' Y / GARAGE O RETAINING WALL/ ❑ YES �.' LOAD CARPORT ROCKERY RENEWAL REMARKS Z (TYPE OF USE. BUSINESS OR ACTIVITY} EXPLAIN: PROGRESS INSPECTIONS PER UBC 305 Q 4i7 J97S-0 N NUMBER OF STORIES o NUMBER OF / C - -�i t m [. •a']'' m DWELLING fhf"t."•^7 UNITS V O DESCRIBE WORK TO BE DONE (ATTACH PLOT PLAN)" '�?�` ', FINAL INSPECTION REQUIRED VALUATION FEE ' 71 PLAN CHECK FEE 7,0 HEATSOURCE: -GLAZING BUILDING /?.,'?� 16C� ./i[J✓ ,.} Q e% l �i / G+ PLUMBING Plan Check No. T MECHANICAL f/) This Permit covers work to be done on private property ONLY. GRADINGIFILL Any construction on the public domain (curbs, sidewalks, driveways, marquees, etc.) will require separate permission. STATE SURCHARGE Permit Application:180 Days Permit Limit:1 Year - Provided Work is Started Wlthin.180 Days STORM DRAINAGE FEE '.Applicant, on behalf of his or her.spouse, heirs, assigns and ENG. INSPECTION FEE insuccessors in interest, agrees to indemnify, defend and hold P f o harmless the City of Edmonds, Washington, its officials,; ACiJJLJ s employees, and agents from any and all Claims for damages of whatever nature, arising directly or indirectly from the Issuance = of this permit. Issuance of this permit shall not be deemed to PLAN CHECK DEPOSIT modify, waive or reduce any requirement of any city: ordinance i nor limit in any way the City's ability to enforce any ordinance TOTAL AMOUNT DUE provision."BA I hereby acknowledge that I have read this application; that the information given is correct; and that I am the owner, or the duly ATTENTION APPLICATION APPROVAL j authorized agent of the owner. I agree to comply with city and THIS PERMIT state laws regulating construction; and in doing the work authoriz- AUTHORIZES This application is not a permit until ad thereby, no person will be employed in violation of the Labor ONLY THE signed by the Building Official or his/her Code of the State of Washington relating to Workmen's Compensa- WORK NOTED Deputy; and fees are paid, and receipt is ti n insurance. NSPECTION acknowledged in space provided. SIGNATURE (OWNER OR AGENT( SIGNED DEPARTMENT OFFIitiSIGN URE DATE I l JDATE O r EDIMONTY S / CALL FOR ATTENTIONNSPEcrtoN GAELEASeb BY- y DATE ` 1 IT IS UNLAWFUL TO USE OR OCCUPY A BUILDING OR STRUCTURE 771-0220 UNTIL A FINAL INSPECTION HAS BEEN MADE AND APPROVAL OR ORIGINAL —File YELLOW— Inspector A CERTIFICATE OF OCCUPANCY HAS BEEN GRANjED. UBC CHAPTER 3. PINK — Owner GOLD — Assessor tebSa RECORD OF INSPECTIONS INSPECTOR DATE APPROVED SETBACKS......... ------ 4 FOUNDATION: Wall .................. Pier/Porch ............. Retaining Wall.......... PLUMBING: Underground .......... RoupA-In ........... CF.. ................... qr HEATING: Gas Test ............... Gas Piping ............. Equipment ............. CF.................... FRAMING ......... SHEETROCK NAILING ... SPECIAL INSPECTION— Z. AjIllo"ACt— FINALAPPROVAL FOR OCCUPANCY vI YY EBFV SEArTLE S111 SHANNON 6WILSON, INC. KENNEWCK GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS FAIRBANKS ANCHORAGE SMUT Lnl im May 7, 1993 Ms. Ursula Schluter ;Z 1701 -2?e 80th Avenue West #4 Edmonds, Washington 98020 RJ CCzl Jut 23 i333 PFRj y�r COU"T R RE: PROPOSED SCHLUTER RESIDENCE, 15620 75 M PLACE WEST, EDMONDS, WASHHINTGTON We have reviewed the letter to the City of Edmonds, dated March 11, 1993, by Landau Associates, Inc., regarding their review of your plans for the proposed Schluter residence at 15620 75th Place West in Edmonds, Washington. In response to that letter we offer the following: The soil conditions described from the 1986 Earth Sciences test pit logs were useful in that they tend to confirm our understanding of the soil conditions in the area and provide.data specific to the subject site. Our recommendations do not rely on the accuracy or detail of those explora- tions, however, as Shannon & Wilson, Inc. will confirm the actual soil conditions at the site during construction of the trench subdrain system and installation of the foundation piles. Both the design of the drainage system and the depth of the piles will be modified as appropriate at that time so that the needs of the project are met. The stability of the Schluter property was increased by construction of the retaining wall along the toe of the slope by Burlington Northern Railroad, and the property has been stable since that wall was constructed. Lowering of the ground water level by the proposed dewatering system will further increase the stability of the site. In our opinion, installing a piezometer to measure porewater pressures is not necessary and would produce no information which is useful at this time. As long as there is no sliding there is no way of knowing or calculating with any degree of certainty the factor of safety against sliding on the hillside. The geotechnical engineer must assume that at the least stable time in the recent history of the site (normally the wettest time of the wettest year) the factor of safety was slightly above 1.0. The site must then be developed in such a way that the stability of the site is further increased. Once a slide develops, the factor of safety of the slope is known (it is 0.999... 9,) and the piezometric level in the soil near the failure plane is an important parame- ter to be used in the slide analysis. However, the piezometric level is not particularly useful until there is a slide to analyze. Ground water was observed to seep from the ground surface during our reconnaissance of the site, indicating that the piezometric level was (is) at or above the ground surface. The proposed trench subdrain will lower the ground water level and prevent it from ever reaching the level W-5385-02 400 NORTH 34TH STREET -SUITE 100 P O. BOX 300303 SEATTLE. WASHINGTON 98103 OnR. R99. Rn9n Feu 9nA. R11. R777 Ms. Ursula Schluter May 7, 4993 Page 2 SHANNON bVVILSON. INC. to which it now exists, thus preventing the factor of safety from dropping to its previous lowest value. There are always risks associated with sloping terrain due to the inherent subterranean unknowns. We have endeavored to provide recommendations for design and construction which . will minimize those risks in a reasonable and cost effective manner. Ms. Schluter has indicated that she is aware of and prepared to accept the risks associated with building and living on hillside property. In response to comments on page 3 of the Landau letter, site access, temporary cut and fill slopes and construction shoring will be the responsibility of the contractor, who must work in compli- ance with WAC 296-155. Grading at the site will be minimal and will have no long term effect on the site stability. The soils an the site are only moderately erodible, and erosion can be controlled by implementation of the wet weather earthwork recommendations presented in our report dated March 19,1990, and through the judicious use of straw bales and/or geotextile silt curtains. Most of the soils excavated during the trench subdrain installation will be removed from the site. A stated in our January 29, 1993 letter, Shannon & Wilson, Inc. has reviewed the geotechnical aspects of the plans for the proposed house and found them in general accor- dance with our recommendations. We appreciate the opportunity to be of service. Sincerely, SHANNON & WILSON, INC. C ._.. EXPIRES 7r25/ 13 s /s 3 Ralph N. Boirum. P.E. Senior Associate RNB:TEK/rnb W538S-03 XTR/W5385-1kd/1kd W-5385-02 W-6114-02 Revised Geolechnical Report Proposed Residence at Lots I and 2, 75th Place West Edmonds, Washington January 1994 Ms. Ursual Schluter 21701 80th Avenue West, #4 Edmonds, Washington 98020 SHANNON bWLSON, INC. GEOTECHNICAL AND ENVIPONMENTAL CONSULTANTS 400 N, 34th St - SLAte 100 P.O. Box 300303 Se-,,affle, Washit-ig-lon 9,81031 206.632-8020 SHANNON 6WI�HANFO ON, INC. E ANFORD FAIRBANKS ® GEOTECHNICAL AND ENVIRONNA ENTAIL CONSULTANTS ANCHORAGE SAINT LOUIS BOSTON January 26, 1994 1 JV4 Ms. Ursula Schluter 21701 80th Avenue West, #4 Edmonds, Washington 98020 RE: REVISED GEOTECHNICAL REPORT, PROPOSED RESIDENCE AT LOTS 1 AND 2, 75TH PLACE VVEST, EDMONDS, WASHINGTON This report presents the results of our geotechnical reconnaissance, subsurface explorations and engineering analyses for your proposed residence on 75th Place West in Edmonds, Washington. This report is a revision of our previous report dated March 29, 1990 and presents additional information for site development and the results of a recently completed subsurface exploration at the site. The purpose of our work was to evaluate the site and provide recommendations to aid in foundation design for the proposed single-family residence. Our work included a reconnaissance of the site, review of our previous work and existing geotechnical reports, and completion of an exploratory soil boring at the site. SITE AND PROJECT DESCRIPTION The property is located on the west side of 75th Place West in the Meadowdale area of Edmonds, Washington. The property measures approximately 97 feet by 190 feet and consists of two lots located about 200 feet riorth of the intersection of 75th Place West and 158th Street S.W. The legal description for the property is: lots 1 & 2, Block 28, Meadowdale Beach, Snohomish County, Washington. The lots are bordered on the east by 75th Place West and on the west by the Burlington Northern Railroad right-of-way. The property is shown on the Site Plan, Figure 1. An occupied lot lies to the south of the subject property and a lot with an abandoned house and shed lies to the north. Portions of the abandoned structures which lie on the lot to the north protrude into the subject property. The ground surface is covered with dense brush and blackberry vines. The site slopes moderately downward from 75th Place West to the BNRR tracks. The average slope is about 1 vertical to 3 horizons (1V to 3H). A retaining wall about 4 feet high has been built by the railroad along the toe of the slope. We understand this wall was constructed to prevent debris from sliding onto the railroad right-of-way. 400NORTh'34THSTREET -SUITE 100 W-5385-02 F O BOX 300303 SEATTLE. WASHINGTON 98103 206.632. 8020 FAX 206.633.6777 Ms. Ursula Schluter January 26, 1994 Page 2 SHANNON 6WILSON, INC. We understand that the proposed residence will be a multi -story, single-family house. A garage and elevated driveway between the house and road will also be constructed. The dimensions of the proposed house are approximately 61 feet long by 48 feet wide. The approximate location of the house is as indicated on the Site Plan, Figure 1. SUBSURFACE EXPLORATIONS The site was explored by means of one soil boring drilled on the east side of the site, as shown on the Site Plan, Figure 1. The location of the boring was obtained by tape measurement from existing features. The boring was drilled to a depth of 61.5 feet . A log of the boring is presented on Figure 3. The soil boring was drilled by Associated Drilling Co. of Seattle under subcontract to Shannon & Wilson, Inc. on November 19, 1993. A truck mounted B-61 drill rig equipped with a 3-3/8-inch I.D. hollow -stem auger was used. Standard Penetration tests were performed at 2.5-foot intervals to a depth of 20 feet and at 5-foot intervals thereafter. The Standard Penetration test consists of driving a 2-inch O.D. split -spoon sampler a distance of 18 inches into the bottom of the borehole with a 140-pound hammer falling 30 inches. The number of blows required to drive the sampler each of three 6-inch increments was recorded, and number of blows required to cause the last 12 inches of penetration is termed the Standard Penetration Resistance (N-value). This value is an indicator of the relative density or consistency of the soils. Samples obtained in the field were classified by a geologist, sealed in jars, and returned to our laboratory where the classification of each sample was visually checked and its moisture content was determined. The results of the Standard Penetration Tests, moisture contents and soil classifications are summarized on the boring log, Figure 3. In addition to the recent soil boring, subsurface explorations were completed by Earth Sciences in February 1986. Test pits TP-2 and TP-3 of the Earth Sciences report were located on the Schluter property (previously the Hodge property). The results of their test pit explorations are presented in Figure 7 and their approximate locations are shown in Figure 1. W-5385-02 Ms. Ursula Schluter SHANNON 8WILSON, INC. January 26, 1994 Page 3 SUBSURFACE CONDITIONS The subsurface conditions at the site are illustrated on the attached Section A -A', Figure 2. The results of the explorations indicate that the site is generally underlain by 8 to 21 feet of slide debris consisting of loose sand, silt, and silty clay. Below the slide debris the soils consist of stiff to very stiff, fine -sandy silt and clayey silt, becoming hard to very stiff silty clay. The stiff to hard silt and clay appears to be glacially consolidated. Considerable groundwater seepage was observed on the surface of the site during our reconnaissance. Seepage was observed during drilling of boring B-1 at a depth of 18 feet. Groundwater flow was also noted on the test pit logs in the report by Earth Sciences. LANDSLIDE HISTORY The Schluter property lies within the Meadowdale landslide complex. Roger Lowe Associates prepared a report titled, "Landslide Hazards Investigation, Meadowdale Area, Edmonds, Washington" in 1979. This report details the geologic history, site geology, and landslide history of the Meadowdale Landslide Complex. According to the above report, the subject area experienced large-scale ground movement two to three thousand years ago. This slide was 3,200 feet long and as much as 650 feet wide. The head scarp is easily distinguished above 75th Place West. The cause of such a large-scale earth movement is inferred to be due to progressive shoreline erosion by wave action. Construction of the Great Northern Railroad (presently owned by Burlington Northern) along the beach has halted the shoreline erosion process. No large-scale earth movements have been recorded for this area in modern times. However, subsequent to the ancient slide, the mass of soil within the body of the slide has experienced numerous small-scale adjustments. This type of post -slide adjustment is common and typically occurs in the form of shallow earth slumps until a more stable slope geometry is achieved. The study by Roger Lowe Associates has indicated that the stability of the Meadow dale area is highly sensitive to ground water levels. Improvements to local site drainage, including the installation of sewers and storm drains has had a positive impact on the stability of the area. W-5385-02 Ms. Ursula Schluter January 26, 1994 Page 4 SHANNON 6WILSON, INC. Review of available records and reports indicates that the Schluter property is located within an area of near -surface slide activity. 'The "Report of Geologic Evaluation, Meadowdale Area, Edmonds, Washington for the City of Edmonds," dated 1968, includes a description of a landslide which occurred in 1955-_ 56. The Schluter property lies within the boundaries of this area. Also, according to the G3reat Northern/Burlington Northern Railroad records, three slides occurred along the section of track (MP 21.6) in the immediate vicinity of the Schluter property between 1949 and 1S�56. The railroad subsequently built retaining walls along the toe of the slope, including along the Schluter property. The records indicate that sliding occurred on properties south Of' Schluter's in 1973-74, but there is no indication that sliding has occurred on the Schluter property since its wall was constructed. REQOMMENDATIONS In our opinion, the existing fill and slide debris which covers the site would not provide suitable support for the proposed structures. We understand that the house design presently calls for augercast piles with diameters of 24 inches. In our opinion, 24-inch-diameter augercast piles, with a minimum penetration of 12 feet into the hard silt would be capable of developing an allowable capacity of at least 25 tons each with an adequate factor of safety. This pile capacity could be increased by 1/3 for seismic loadings. We expect that settlement of properly installed piles or piers at this site would be negligible. We expect that the bearing stratum will be located at depths ranging from about 15 to 25 feet at the building site and piles should penetrate at least 12 feet into the hard, gray silty clay. Based on the results of the explozations, we estimate that foundation piles will extend about 40 feet below the existing grounci surface. The depth to the bearing stratum for each pile should be determined by a geotechnical engineer or his representative during construction. In order to provide stiffness against potential soil creep, we recommend that the building foundations be tied together in the up -and -down -slope direction with a grade beam. This beam should have moment connections with the tops of the piles. The piles and grade beam will form a stiff structural system to resist soil movement in the downslope direction. In order to increase the stability of the site we recommend that at least one trench subdrain be installed across the site in roughly a north -south direction, at the approximate location W-5385-02 Ms. Ursula Schluter January 26, 1994 Page 5 SHANNON 6WILSON. INC. shown in Figure 1. Subdrains would consist of a 6-inch (minimum) diameter slotted plastic pipe bedded in 3/8-inch pea gravel in the bottom of a sand -filled trench. The location of the trench subdrain will depend on design of the house, and should be determined after the layout of the house has been established in the field. We recommend that no additional fill be placed on the site, as the additional weight could reduce the stability of the site. Much of the soil excavated from trench subdrains should be removed form the site, although some may be used as backfill in the upper 4 or 5 feet of the trench. We should review any plans for placement of fill on this site so that unstable conditions are not created. It is our opinion that the proposed structure, supported on augercast concrete piles, will not experience significant lateral deflections or settlement. With regard to utility connections, we do not foresee the need for flexible utility connections for the proposed structure. Site Stability The results of our studies indicate that the property can be developed and the proposed residence constructed in such a way as to increase the stability of the site. We expect that construction of a trench drain across the property will lower the ground water level and increase the stability of the site. In our opinion, once this site is developed in accordance with our recommendations, the probability of substantial loss due to future sliding will be less than 30 percent in a 25-year period. Excavation for the recommended trench subdrain will result in an increased possibility of local sliding in the immediate vicinity of the trench. This risk of sliding would be limited to within about 30 feet of the excavation and would not endanger the street or neighboring properties. The use of a trench box and immediately backfilling the completed trench to minimize the length of excavation open at any one time will minimize the potential for sliding during construction. Completed portions of the trench will immediately begin to drain the site, and the stability of the site should increase as the work proceeds. Concrete Piles Augercast piles are installed by rotating a continuous -flight hollow -stem auger to a pre- determined depth. When the depth is reached, a high strength sand -cement grout is pumped, W-5385-02 Ms. Ursula Schluter January 26, 1994 Page 6 SHANNON &WILSON, INC. under controlled pressure, through the center of the shaft as the auger.is slowly withdrawn. By maintaining pressure in the grout line and slowly extracting the auger no faster than an equivalent volume of grout is pumped, a continuous column of concrete is formed. A single large reinforcing rod can be installed for the full pile length through the hollow -stem of the auger, and/or a reinforcing cage can be placed in the column of wet grout. The quality of augercast concrete piles is primarily dependent on the procedures and workmanship of the Contractor who installs them. A properly functioning pressure gage and pump stroke counter or flow meter should be provided on the grout pump to assist in monitoring augercast pile installation. The auger should be withdrawn with slow positive rotation at a slow steady pull and should not be pulled until the grout has been pumped a few feet above the tip. Lateral Earth Pressures and Retaining Structures Lateral forces from wind, seismic, and earth pressures or other loadings would be resisted by passive earth pressure against the buried portions of structures, and from lateral pile resistance. In our opinion, lateral earth pressures in the downslope direction could be estimated using an equivalent fluid weight of 35 pounds per cubic foot (pcf), plus one pound per cubic foot for each degree of upward inclination of the backslope above the wall. This pressure should be assumed to act over three times the diameter of the pile to a depth of 5 feet. This active lateral force will be resisted by passive pressure against the portion of the piles below a depth of 5 feet. An equivalent fluid weight of 280 pcf may be used to estimate the passive resistance against the down -slope sides of the piles and should be assumed to act over twice the pile diameter. This value may also be used to estimate passive resistance in the cross -slope directions. The lateral capacity of piles will depend on the size and stiffness of the pile. Battered piles can also be installed to carry lateral loads, if necessary. Below -grade walls and grade beams of the proposed structure should be designed for an equivalent fluid pressure of 55 pounds per cubic foot (pcf), plus one pound per cubic foot for each degree of upward inclination of the backslope above the wall. Cantilevered retaining walls which are not connected to the house could be designed for an equivalent fluid pressure of 35 pcf, plus one pound per cubic foot for each degree of upward inclination of the backslope above the wall. These pressures assume the walls are drained so that W-5385-02 Ms. Ursula Schluter January 26, 1994 Page 7 SHANNON &WILSON, INC. hydrostatic pressures cannot devevelop. Recommendations for wall drainage and backfilling are presented on Figure 6. We recommend that a coefficiemtnt of friction of 0.5 be used between cast -in -place concrete and soil for nonpile-supported sz structures. Base friction should not be considered beneath pile supported portions of the sttatructure. A trench box may be required fi for installation of the drainage trench. Lateral earth pressures for design of trench-bdbox shoring are presented in the attached Figure 4. Drainage Because of the large amount of T groundwater seepage at this site, development should include the installation of one or more tt trench subdrains to lower the groundwater level and improve the stability of the site. We exgzpect that at least one trench subdrain will be required, extending roughly north -south as across the property as shown on Figure 1. A typical trench subdrain instalI0lation is shown on Figure 5. The subdrains should consist of a 6-inch (minimum) diametener slotted plastic pipe surrounded by at least 8 inches of 3/8- inch pea -gravel at the bottom o$of a trench. The trench backfill should consist of drainage sand and gravel, gradation spec:xifications of which are presented on Figure 5. Native site soils do not meet the requiremesents for drainage sand and gravel. The trench subdrains should exttxtend to a depth of 8 to 15 feet, or 1-foot below the contact between the fill/slide debris andbd the stiff to hard native soils. It should drain south to the property line and, if possible, szshould be connected with a tightline to the existing storm water drainage system which ruuuns up and down the slope near the south property line. We expect that the trench excavwation can be completed with open cut methods using stable side slopes; however, a trench-b-box shoring system should be used where appropriate. Installation of the subdrain trenonch should begin at the lower end and proceed up -slope. The pipe should be installed and the9e trench should be backfilled with drainage materials as the excavation proceeds, so that no0ot more than about 30 feet of trench is open at a time. This will reduce the potential for caw-ving and local sliding during trench installation. It may be W-5385-02 Ms. Ursula Schluter January 26, 1994 Page 8 SHANNON &WILSON, INC. necessary to periodically stop work for a day or two to let the site drain before advancing the trench. Footing drains consisting of 6-inch-diameter slotted plastic pipe should be installed on the upslope side of any below -grade walls and grade beams. Freely draining sand or sand and gravel should be used as backfill. Wall drainage and backfill recommendations are presented on Figure 6. The downspout water from the structure should be conveyed to a suitable discharge point, such as the existing storm drainage system, in a tightline. Subsurface drainage and downspout water should not flow onto the ground surface below the structure or onto the slope and should not flow into perforated footing drains. Erosion Control Erosion at the site during construction can be minimized by implementing the rec- ommendations in the Wet Weather Earthwork section, and can be controlled through the judicious use of fabric silt curtains and/or straw bales. The site should be seeded as soon as possible after grading, and vegetation should be encouraged. Wet Weather Earthwork The soils at the site are generally moisture sensitive, and will become soft and difficult to work when wet. Pile installation and other earthwork should not be accomplished during periods of heavy rainfall. If earthwork is to be accomplished in wet weather or under wet conditions when control of soil moisture content is not possible, fill should contain no more than 5 percent material passing the.No. 200 mesh sieve, by weight, based on the minus 3/4 inch fraction. In addition: a) Earthwork should be accomplished in small sections and carried through to completion to minimize exposure to wet weather. If there is to be traffic over the exposed subgrade, the subgrade should be protected with a compacted layer of clean sand and gravel or crushed rock. The size or type of equipment may have to be limited to prevent soil disturbance; b) No soil should be left uncompacted so it can absorb water. Soils which become too wet for compaction should be removed and replaced with clean granular material; and, W-5385-02 Ms. Ursula Schluter SHANNON WILSON, INC. January 26, 1994 Page 9 c) Excavation and placement of fill should be observed on a full time basis by a person experienced in wet weather earthwork to determine that all unsuitable materials are removed and suitable compaction and site drainage is achieved. We recommend that these recommendations for wet weather earthwork be included in the contract specifications. Construction Monitoring and Plans Review We have worked with your architect and engineer in the design of foundations for the proposed structure and the necessary drainage installations at the site. We have also reviewed the portions of the plans which pertain to earthwork and foundations to determine that they are consistent with our recommendations. We recommend that we be retained to monitor earthwork construction, including drainage and augercast pile installations, to determine that the work is accomplished in a suitable manner. Installation of the trench subdrain and foundation piles should be monitored on a full time basis. This monitoring should include verifying the depth of competent bearing soil and measurement of the volume of grout placed into each pile. LIMITATIONS The conclusions and recommendations presented in this report are based on site conditions as they presently exist and assume the subsurface conditions are not significantly different from those indicated in the explorations performed by Shannon & Wilson, Inc. or others. If during construction, subsurface conditions different from those encountered in the explorations and site reconnaissance are observed or appear to be present, we should be advised at once so that we can review those conditions and reconsider our recommendations where necessary. If there is a substantial lapse of time between submission of our report and the start of work at the site, or if conditions have changed due to natural causes or construction operations at or near the site, it is recommended that this report be reviewed to determine the applicability of the conclusions and recommendations considering the changed conditions and time lapse. This report was prepared for the use of the Owner or Engineer/Architect in the design of the structure. It should be made available to prospective contractors and/or the Contractor for information on factual data only and not as a warranty of subsurface conditions. To assist you and others in understanding the use and limitations of our report, Shannon & Wilson, Inc. has prepared the attachment "Important Information About Your Geotechnical Engineering Report. " W-5385-02 Ms. Ursula Schluter January 26, 1994 Page 10 SHANNON &WILSON, INC. The scope of our work did not include environmental assessments or evaluations regarding the presence or absence of wetlands or hazardous or toxic substances in the soil, surface water, groundwater on or below this site. Unanticipated conditions are commonly encountered and cannot be fully determined by merely performing a site reconnaissance, taking soil samples or making explorations. Such unexpected conditions frequently require that additional expenditures be made to achieve a properly constructed project. Some contingency fund is recommended to accommodate such potential extra costs. We appreciate your continued confidence in our firm, please call if you have any questions. Sincerely, SHANNON & WILSON, INC. w t' 1 4764 FCIS(ERt'' r:xP mEs 7/25/ 9 Ralph N. Boirum, P.E. Senior Associate RNB:TEK/mb Enclosures: Figure 1 - Site Plan Figure 2 - Subsurface Profile A -A' Figure 3 - Log of Boring B-1 Figure 4 - Lateral Earth Pressures Figure 5 - Typical Trench Subdrain Installation Figure 6 - Typical Foundation Subdrain And Backfill Figure 7 - Test Pit Logs Important Information About Your Geotechnical Engineering Report W 53 85-02 XT4/ W53 85-1kd/1kd W-5385-02 W P NOTE ------------- - 30 N 80 09' 48" W I \190.75 off - Base map taken from topographic survey map by Group Four, Inc., dated March 6, 1990. TP-3 \ •°�� D21 18 -Oif N 91' 57" % 0 10 20 4i 1-- Scale in LEGE B-1 & Boring Designation volegivialtim Trench Drain LocE TP-1 1%i Test Pit Designati4 completed Februa A +— Generalized Subs A West 120 100 80 40 20 NOTE This profile is generalized from materials encountered in field explorations. Variations between this profile and actual conditions may exist. Subsurface conditions between boring locations are not known. Geologic contacts are interpreted; actual contacts may vary significantly. 0 10 2 Scale i Horizontal LEG TP-3 --Test Pit D B-1 Boring De (Prof. 32' S.)—Offset Di; ? —L ? Approxim Bottom of SOIL DESCRIPTION LL rn a v u Standard Penetration Resistance r - a = ': r (140 lb. weight, 30" drop) CL o m ° a ♦ Blows per foot Surface Elevation: 98 Feet p to to p 0 20 40 60 Loose, brown, silty, fine SAND; moist; wet @ 18 ft. mixed with clayey SILT with = .: . . . mottled disturbed appearance with = possible slide plane @ 20 ft. (Fill and _ 10 ......__.._..........._..._.............._ .....:......__._.............._....._._...;..._.. . .. Slide Debris) SM. = 20.9 20 _...... Stiff to very stiff, gray, fine sandy SILT to = .. ..... slightly clayey SILT; wet; with laminated = o is ::::: structure; ML. 30 ....:.. ...... - 36.0 = Hard, gray, silty CLAY; moist; laminated with fine sand partings and wet sand layer = 40 :......................_........................._._........_.............. ;...._._..........._._..__... ..._...._._.... at 46.3 ft.; CL. 50 .. .... _ :...__..:. _ ___:....... -- 56.0 = ... Very stiff, gray, silty CLAY; moist; with scattered iron stained sand layers and = 60 .__._.._..__.....__..__................:.__..........___ .....__.� _...__..._._......__..___._._. disturbed blocky appearance; (Possible s1.5 ancient slide plane) CL. BOTTOM OF BORING COMPLETEDON 11 /19/93 70 .................. ............ ............... ............... .......... ........... ................... .... ............. ...... _._._......_._._.._ 80 -..:.__:..:-... --............... .....:__......:...:____..____.._�...:....._..:___.._:._._... ....:_..:.__..:._. 90 ........:__............. ..:.....:_......:..........:.....:...:....:....:....:.._............... .... ... _......... O 20 40 60 LEGEND • % Water Content " Sample Not Recovered Surface Seal Plastic Limit Liquid Limit = 2" O.D. Split Spoon Sample ® Annular Sealant Naturall WWater ater C Content ZL 3" O.D. Shelby Tube Sample Piezometer Screen ® Grout Ursula Schluter SZ Water Level - 15620 75th Place West Edmonds, Washington NOTES 1. The stratification lines represent the approximate boundaries between LOG OF BORING B-1 soil types, and the transition may be gradual. 2. The discussion in the text of this report is necessary for a proper understanding of the nature of subsurface materials. January 1994 W-5385-02 3. Water level, if indicated above, is for the date specified and may vary. 4. Refer to KEY for explanation of 'Soil Log' symbols and definitions. SHANNON & WILSON, INC. FIG. 3 5. USC letter symbol based on visual classification. caotechnical and Environmental consultants VERY SOFT TO SOFT SILTS AND CLAYS 3 FT. MIN. —� �-- AVER-AGE HEIGHT HA I EXCAVATED MATERIAL STEEL TRENCH / BOX - MAKE EXCAVATION SLIGHTLY WIDER H THAN WIDTH OF BOX TO PERMIT BOX TO BE PULLED THROUGH TRENCH I50H psf "HA psf (SURCHARGE DUE TO EXCAVATED MATERIAL) LATERAL EARTH PRESSURE FOR STEEL TRENCH BOX 3 FT. MIN.—� �— AVERAGE H I F HEIGHT A EXCAVATED MATERIAL 0.25 SHORING SYSTEM H TRENCH 50H psf 50Fk psf (SURCHARGE DUE TO EXCAVATED MATERIAL) LATERAL EARTH PRESSURE FOR BRACED EXCAVATION NOTES 1. H AND HA ARE HEIGHTS IN FEET. 2. HYDROSTATIC PRESSURES SHOULD BE ADDED TO THE ABOVE VALUES WHERE APPLICABLE. 3. THE CONDITIONS OF BOTTOM HEAVE SHOULD BE STUDIED. 4. EXCAVATED SOIL SHOULD BE STOCKPILED AT LEAST 3 FEET FROM THE EXCAVATION, AND FURTHER AS INDICATED BY BOTTOM HEAVE STUDIES. Existing Ground Surface 1-Ft. On -site Soil «,. Trench Excavation Drainage Sand and r v I B ckfill> >> .Gae a ><`<' 6-in. Minimum Diameter Slotted Plastic Pipe Washed 3/8" Pea Gravel (8" min. above pipe, 12" on sides, 4" below) Trench Bottom and Subdrain Pipe Sloped to Drain SPECIFICATIONS FOR DRAINAGE SAND AND GRAVEL Percent Passing Not to Scale Sieve Size by Weight 1-1/2 100 Ursula Schluter Residence 3/4 90 - 100 Edmonds, Washington 1 /4 75 - 100 No. 8 65 - 92 TYPICAL TRENCH SUBDRAIN No. 30 20 - 65 INSTALLATION No. 50 5 - 20 No. 100 0-2 January 1994 W-5385-02 (by wet sieving) (non -plastic) SHANNON & WILSON, INC. FIG. 5 Geotechnicel and Environmental Consultants Pavement or 8" Impervious Soil Excavation Slope (Contractors Responsibility) 8" Min. Cover of 3/8" Pea Gravel Over Pipe Sloped to Drain Away From Basement or Structure Retaining Wall Washed 3/8" Pea Gravel o 0 0 �0 o or Clean Sand and Gravel n Granular • a e Backfill (See Note 1) " 18' Damp Proofing Min.Ob o c °• 0 o0 0 Weep Holes o " ° ° (See Note 1) ooo< ° Floor Slab Subdrain Pipe Not to Scale NOTES 1. Wall backfill should consist of freely draining granular soil with no more than 5% (by weight based on the minus 3/4-inch portion) passing the No. 200 sieve (by wet sieving), with no plastic fines. 2. Backfill behind the wall should be compacted with hand -operated equipment. Heavy equipment should not be used as such equipment operated near the wall could increase lateral earth pressures and possibly damage the wall. 3. Backfill should be placed in layers not exceeding 6" loose thickness, and should be densely compacted. Beneath paved areas, compact to at least 95% of the Modified Proctor maximum dry density ( ASTM: D1557-70), otherwise compact to 92% compaction. Washed Pea Gravel Vapor Barrier 6" Min. of iono n IKI nin= 4" minimum diameter perforated or slotted plastic pipe; tight joints; sloped to drain (6'/100' min. slope). Provide clean -outs. TEST PIT LOGS Al 0' - Duff, topsoil, and roots 1:3' - Variable brown silty fine sand .with gravel and clasks of silt -clay mixture (slide debris) (loose) 13.0' - Completed February 25, 1986; no groundwater encountered #2 0' - Duff, topsoil, and roots 1.1' - Variable sandy silt and silty sand (slide debris) ±13.5' - Sandy gravel, slight groundwater seepage throughout ±15.5' - Blue -gray silty clay (severely fissured and with slickensides) ±17.0' - Completed February 25, 1986 A3 0' - Variable silt -sand -gravel mixture (saturated) (slide debris) 3.0' - Blue -gray silty clay (med stiff) (old slide debris) 8.1' - Tan silt (hard) 14.5' - Completed February 25, 1986; groundwater flow from upper 3 feet #4 0' - Highly variable silt -sand -clay mixture (slide debris) 7.0' - Blue -gray silty clay (fissured, ancient slide debris) 11.0' - Tan silt (hard) 13.0' - Blue -gray silt (hard) 16.0' - Completed February 25, 1986; seepage from 4-7 feet FIG. 7 W-5385-02 SHANNON & WILSON, INC. Geotechnical and Environmental Consultants Attachment to Report Page 1 of 2 Dared: January 26, 1994 To: Ms Ursula Schluter Edmonds, Washington Important Information About Your Geotechnical Engineering/ Subsurface Waste Management (Remediation) Report GEOTECHNICAL SERVICES ARE PERFORMED FOR SPECIFIC PURPOSES AND PERSONS. Consulting geotechnical engineers prepare reports to meet the specific needs of specific individuals. A report prepared for a civil engineer may not be adequate for a construction contractor or even another civil engineer. Unless indicated otherwise, your consultant prepared your report expressly for you and expressly for purposes you indicated. No one other than you should apply this report for its intended purpose without first conferring with the consultant. No party should apply this report for any purpose other than that originally contemplated without first conferring with the geotechnical engineer/geoscientist. AN ENGINEERING REPORT IS BASED ON PROJECT -SPECIFIC FACTORS. A geotechnical engineering/subsurface waste management (remediation) report is based on a subsurface exploration plan designed to consider a unique set of project -specific factors. Depending on the project, these may include: the general nature of the structure and property involved; its size and configuration; its historical use and practice; the location of the structure on the site and its orientation; other improvements such as access roads, parking lots, and underground utilities; and the additional risk created by scope - of -service limitations imposed by the client. To help avoid costly problems, have the consulting engineer(s)/scientist(s) evaluate how any factors which change subsequent to the date of the report, may affect the recommendations. Unless your consulting geotechnical/ civil engineer and/or scientist indicates otherwise, your report should not be used: 1) when the nature of the proposed project is changed (for example, if an office building will be erected instead of a parking garage, or if a refrigerated warehouse will be built instead of an unrefrigerated one, or chemicals are discovered on or near the site); 2) when the size, elevation, or configuration of the proposed project is altered; 3) when the location or orientation of the proposed project is modified; 4) when there is a change of ownership; or 5) for application to an adjacent site. Geotechnical/civil engineers and/or scientists cannot accept responsibility for problems which may occur if they are not consulted after factors which were considered in the development of the report have changed. SUBSURFACE CONDITIONS CAN CHANGE. Subsurface conditions may be affected as a result of natural changes or human influence. Because a geotechnical/waste management engineering report is based on conditions which existed at the time of subsurface exploration, construction decisions should not be based on an engineering report whose adequacy may have been affected by time. Ask the geotechnical/waste management consultant to advise if additional tests are desirable before construction starts. For example, groundwater conditions commonly vary seasonally. Construction operations at or adjacent to the site and natural events such as floods, earthquakes, or groundwater fluctuations may also affect subsurface conditions and, thus, the continuing adequacy of a geotechnical/waste management report. The geotechnical/civil engineer and/or scientist should be kept apprised of any such events, and should be consulted to determine if additional tests are necessary. MOST GEOTECHNICAL RECOMMENDATIONS ARE PROFESSIONAL JUDGMENTS. Site exploration and testing identifies actual surface and subsurface conditions only at those points where samples are taken. The data were extrapolated by your consultant who then applied judgment to render an opinion about overall subsurface conditions. The actual interface between materials may be far more gradual or abrupt than your report indicates. Actual conditions in areas not sampled may differ from those predicted in your report. While nothing can be done to prevent such situations, you and your consultant can work together to help minimize their impact. Retaining your consultant to observe subsurface construction operations can be particu- larly beneficial in this respect. A REPORT'S CONCLUSIONS ARE PRELIMINARY. The conclusions contained in your geotechnical engineer's report are preliminary because they must be based on the assumption that conditions revealed through selective exploratory sampling are indicative of actual conditions throughout a site. Because actual Page 2 of 2 subsurface conditions can be discerned only during earthwork, you should retain your geotechnical engineer to observe actual conditions and to finalize conclusions. Only the geotechnical engineer who prepared the report is fully familiar with the background information needed to determine whether or not the report's recommendations based on those conclusions are valid and whether or not the contractor is abiding by applicable recommendations. The geotechnical engineer who developed your report cannot assume responsibility or liability for the adequacy of the report's recommendations if another party is retained to observe construction. THE GEOTECHNICAL ENGINEERING/SUBSURFACE WASTE MANAGEMENT (REMEDIATION) REPORT IS SUBJECT TO MISINTERPRETATION. Costly problems can occur when other design professionals develop their plans based on misinterpretation of a geotechnical engineering/subsurface management (remediation) report. To help avoid these problems, the geotechnical/civil engineer and/or scientist should be retained to work with other project design professionals to explain relevant geotechnical, geological, hydrogeological and waste management findings and to review the adequacy of their plans and specifications relative to these issues. BORING LOGS AND/OR MONITORING WELL DATA SHOULD NOT BE SEPARATED FROM THE ENGINEERING/WASTE MANAGEMENT REPORT. Final boring logs developed by the geotechnical/civil engineer and/or scientist are based upon interpretation of field logs (assembled by site personnel), field test results, and laboratory and/or office evaluation of field samples and data. Only final boring logs and data are customarily included in geotechnical engineering/waste management reports. These final logs should not, under any circumstances, be redrawn for inclusion in architectural or other design drawings, because drafters may commit errors or omissions in the transfer process. To minimize the likelihood of boring log or monitoring well misinterpretation, contractors should be given ready access to the complete. geotechnical engineering/waste management report prepared or authorized for their use. If access is provided only to the report prepared for you, you should advise contractors of the report's limitations, assuming that a contractor was not one of the specific persons for whom the report was prepared and that developing construction cost estimates was not one of the specific purposes for which it was prepared. While a contractor may gain important knowledge from a report prepared for another party, the contractor should discuss the report with your consultant and perform the additional or alternative work believed necessary to obtain the data specifically appropriate for construction cost estimating purposes. Some clients hold the mistaken impression that simply disclaiming responsibility for the accuracy of subsurface information always insulates them from attendant liability. Providing the best available information to contractors helps prevent costly construction problems and the adversarial attitudes which aggravate them to a disproportionate scale. READ RESPONSIBILITY CLAUSES CLOSELY. Because geotechnical engineering/subsurface waste management (remediation) is based extensively on judgment and opinion, it is far less exact than other design disciplines. This situation has resulted in wholly unwarranted claims being lodged against geotechnical/ waste management consultants. To help prevent this problem, geotechnical/civil engineers and/or scientists have developed a number of clauses for use in their contracts, reports and other documents. These responsibility clauses are not exculpatory clauses designed to transfer the engineer's or scientist's liabilities to other parties; rather, they are definitive clauses which identify where the engineer's or scientist's :responsibilities begin and end. Their use helps all parties involved recognize their individual responsibilities and take appropriate action. Some of these definitive clauses are likely to appear in your report, and you are encouraged to read them closely. Your engineer/scientist will be pleased to give full and frank answers to your questions. The preceding paragraphs are based on information provided by the ASFE/Association of Engineering Firms Practicing in the Geosciences, Silver Spring, Maryland 1/93 ao 7s , SHANNON 8WILSON INC SEATTLE EVERETT � • KEPINEWIGK mom GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS FAIRBANKS ANCHORAGE SAINT LOUIS January 29, 1993 Ms. Ursula Schluter 2701 80th Avenue West, #4 Edmonds, Washington 98020 RE: GEOTECHNICAL DECLARATION AND STATEMENT OF RISK, PROPOSED RESIDENCE AT 15620 75TH PLACE WEST, EDMONDS, WASHINGTON Dear Ms. Schluter: We have reviewed the plans for the proposed residence at 15620 75th Place West in Edmonds, Washington, and our comments were presented in a letter dated July 17, 1992. I our opinion, the plans and specifications conform to the recommendations in our geotechnical report. In our opinion, the risk of damage to the proposed development or to adjacent properties from soil instability will be minimal, subject to the conditions set forth in the report. As a result of the drains to be installed, the proposed development will result in a net increase in stability of the site; therefore, the proposed development will not increase the potential for soil movement. There is no way to accurately determine the statistical probability of earth movement; however, once the proposed development is completed in accordance with our recommendations, we believe the risk of significant earth movement at the site will be very small. We appreciate the opportunity to be of service. Sincerely, SHANNON & WILSON, INC. Ralph N. Boirum, P.E. Senior Associate RNB/jnd W5385-02 XTR/W5385-02-Ikd/jnd 400 NORTH 34TH STREET -SUITE 100 P.O. 80X 300303 SEATTLE, WASHINGTON 98103 206.632.8020 FAX 206.633 ^ 6777 W-5385-02 i ' Ms. Ursula Schluter January 26, 1994 Page 5 SHANNON 6WILSON, INC. shown in Figure 1. Subdrains would consist of a 6-inch (minimum) diameter slotted plastic pipe bedded in 3/8-inch pea gravel in the bottom of a sand -filled trench. The location of the trench subdrain will depend on design of the house, and should be determined after the layout of the house has been established in the field. We recommend that no additional fill be placed on the site, as the additional weight could reduce the stability of the site. Much of the soil excavated from trench subdrains should be removed form the site, although some may be used as backfill in the upper 4 or 5 feet of the trench. We should review any plans for placement of fill on this site so that unstable conditions are not created. It is our opinion that the proposed structure, supported on augercast concrete piles, will not experience significant lateral deflections or settlement. With regard to utility connections, we do not foresee the need for flexible utility connections for the proposed structure. Site Stability The results of our studies indicate that the property can be developed and the proposed residence constructed in such a way as to increase the stability of the site. We expect that construction of a trench drain across the property will lower the ground water level and increase the stability of the site. In our opinion, once this site is developed in accordance with our recommendations, the probability of substantial loss due to future sliding will be less than 30 percent in a 25-year period. IExcavation for the recommended trench subdrain will result in an increased possibility of local sliding in the immediate vicinity of the trench. This risk of sliding would be limited to within about 30 feet of the excavation and would not endanger the street or neighboring properties. The use of a trench box and immediately backfilling the completed trench to I minimize the length of excavation open at any one time will minimize the potential for sliding during construction. Completed portions of the trench will immediately begin to drain the site, and the stability of the site should increase as the work proceeds. Concrete Piles Augercast piles are installed by rotating a continuous -flight hollow -stem auger to a pre- determined depth. When the depth is reached, a high strength sand -cement grout is pumped, W-5385-02 CITY Copy W-5385-02 _ SHANNON & WILSON, INC. Over _ Geotechnical. & Environmental Consultants 38 Years of Excellence 400 North 34th Street, Suite 100 • P.O. Box 300303 • Seattle, WA 98103 • (206) 632-8020 • Fax: (206) 633-6777 July 17, 1992 Ms. Ursula Schluter 21701 80th Avenue West #4 Edmonds, Washington 98020 RE: PLAN REVIEW FOR PROPOSED RESIDENCE 15620 75TH PLACE WEST, EDMONDS WASHINGTON Dear Ms. Schluter: This letter presents the results of our plan review for the proposed construction of a single-family residence at the above property. The property is identified as Lots 1 and 2 of Meadowdale Beach area in Edmonds. Our review of the project is based on the set of drawings provided to us by Ms. Ursula Schluter, and on our previous geotechnical studies for the project; refer to our geotechnical report dated March 29, 1990. CONCLUSIONS AND RECOMMENDATIONS In our judgement, with respect to overall slope stability considerations, the plans in general conform to the recommendations in our March 29, 1990 geotechnical report. The risk of damage to the proposed development from soil instability will be minimal, in our opinion, subject to conditions set forth in the geotechnical report; and the proposed development will not increase the potential for soil movement, nor increase the risk of instability for adjacent properties if our recommendations are followed. Installation of the proposed trench subdrain.should result in an increase in the stability of the site. It should be noted that the.geotechnical report presents recommendations regarding some soils - related aspects for the project which are not specifically shown on the plans. This includes recommendations regarding installation of augercast piles, and surface and subsurface drainage measures including the trench subdrain installation. It is recommended that the geotechnical Seattle • Everett • Kennewick • Fairbanks • Anchorage • St. Louis PRESIDENT: Earl A. Sibley, P.E. SR. VICE PRESIDENT: Atef A. Azzam; Raymond P. Miller, P.E.; Harvey W. Parker, P.E.; George Yamane, P,E. VICE PRESIDENT: Herman H. (Tex) Druebert, P.E.: Richard H. Gates, P.E.; W. Paul Grant, P.E.; Leland B. Jones, P.E.; Thomas E. Kirkland, P.E.; Dexter N. McCulloch, C.E.G.; Gerry Millar, R.G.; Frank W. Pita, P.E., P.G.; Ming-Jiun (Jim) Wu, P.E. CONSULTANT: William L. Shannon, P.E. c •• w Ms. Ursula Schluter July 17, 1.992 Page 2 W-5385-02 report be referenced on the plans and/or contract documents, so that our recommendations can be followed as appropriate. Further, it is recommended that the typical trench subdrain detail from our geotechnical report (Figure 2) be shown on the drawings. The drawings indicate approximate locations of two trench subdrains extending approximately north -south across the property. In our opinion, depending upon soil and groundwater conditions encountered during test pit excavation at the start of construction, it may be appropriate to install only one trench subdrain. The trench subdrain should be field -located by us based on several test pits excavated on the site immediately prior to subdrain installation. The plans indicate that 24-inch diameter augercast piles will be installed with a minimum penetration of 16 feet into the firm native soil. The pile size and penetration are greater than that recommended in our report of March 29, 1990, but are acceptable. In our opinion, the proposed piles should be capable of developing an allowable capacity of at least 20 tons. We recommend that the proposed pile locations and approximate pile lengths at each location be indicated on the site plan. The actual lengths, however, should be determined in the field by a geotechnical engineer, based on soil conditions encountered during drilling. If you or your representatives have any questions, please call. We look forward to assisting you With geotechnical construction monitoring for this project. Sincerely, SHANNON & WILSON, INC. Aa 1.aA Qurt Sandeep Puri Engineer SP:RNB:TEK/sp W5385-02.LTR/SP-Ikd/dgw irr L Ralph Boirum, P.E. Senior Associate SHANNON- & WILSON, INC. CITY Copy W-5385-02 SHANNON & WILSON, INC. Over j=� Geotechnical & Environmental Consultants 38 Yea Excellence o 400 North 34th Street, Suite 100 • P.O. Box 300303 • Seattle, WA 98103 • (206) 632-8020 • Fax: (206) 633-6777 July 17, 1992 Ms. Ursula Schluter 21701 80th Avenue West #4 Edmonds, Washington 98020 RE: PLAN REVIEW FOR PROPOSED RESIDENCE 15620 75TH PLACE WEST, EDMONDS WASHINGTON Dear Ms. Schluter: This letter presents the results of our plan review for the proposed construction of a single-family residence at the above property. The property is identified as Lots 1 and 2 of Meadowdale Beach area in Edmonds. Our review of the project is based on the set of drawings provided to us by Ms. Ursula Schluter, and on our previous geotechnical studies for the project; refer to our geotechnical report dated March 29, 1990. CONCLUSIONS AND RECOMMENDATIONS In our judgement, with respect to overall slope stability considerations, the plans in general conform to the recommendations in our March 29, 1990 geotechnical report. The risk of damage to the proposed development from soil instability will be minimal, in our opinion, subject to conditions set forth in the geotechnical report; and the proposed development will not increase the potential for soil movement, nor increase the risk of instability for adjacent properties if our recommendations are followed. Installation of the proposed trench subdrain should result in an increase in the stability of the site. It should be noted that the geotechnical report presents recommendations regarding some soils - related aspects for the project which are not specifically shown on the plans. This includes recommendations regarding installation of augercast piles, and surface and subsurface drainage measures including the trench subdrain installation. It is recommended that the geotechnical Seattle • Everett • Kennewick • Fairbanks • Anchorage • St. Louis PRESIDENT: Earl A. Sibley, P.E. SR. VICE PRESIDENT: Atef A. Auam; Raymond P. Miller, P.E.; Harvey W. Parker, P.E.; George Yamane, P.E. VICE PRESIDENT: Herman H. (Tex) Druebert, P.E.: Richard H. Gates, P.E.; W. Paul Grant, P.E.; Leland B. Jones, P.E.; Thomas E. Kirkland, P.E.; Dexter N. McCulloch, C.E.G.; Gerry Millar, R.G.; Frank W. Pita, P.E., P.G.; Ming-Jiun (Jim) Wu, P.E. CONSULTANT: William L. Shannon, P.E. aMs. Ursula Schluter July 17, 1992 Page 2 W-5385-02 report be referenced on the plans and/or contract documents, so that our recommendations can be followed as appropriate. Further, it is recommended that the typical trench subdrain detail from our geotechnical report (Figure 2) be shown on the drawings. The drawings indicate approximate locations of two trench subdrains extending approximately north -south across the property. In our opinion, depending upon soil and groundwater conditions encountered during test pit excavation at the start of construction, it may be appropriate to install only one trench subdrain. The trench subdrain should be field -located by us based on several test pits excavated on the site immediately prior to subdrain installation. The plans indicate that 24-inch diameter augercast piles will be installed with a minimum penetration of 16 feet into the firm native soil. The pile size and penetration are greater than that recommended in our report of March 29, 1990, but are acceptable. In our opinion, the proposed piles should be capable of developing an allowable capacity of at least 20 tons. We recommend that the proposed pile locations and approximate pile lengths at each location be indicated on the site plan. The actual lengths, however, should be determined in the field by a geotechnical engineer, based on soil conditions encountered during drilling. If you or your representatives have any questions, please call. We look forward to assisting you with geotechnical construction monitoring for this project. Sincerely, SHANNON & WILSON, INC. A at., % Sandeep Puri Engineer SP:RNB:TEKJsp W5385-02.L7R/SP-lkd/dgw l4Z Ralph Boirum, P.E. Senior Associate SHANNON & WILSON. INC. W-5385-01 SHANNON & WILSON, INC. over - Geotechnical Consultants 35 Years or Engineering and Applied Geosciences Excellence 400 North 34th Street, Suite 100 • P.O. Box C-30313 • Seattle, WA 98103 • (206) 632-8020 • Fax: (206) 547-0386 March 29, 1990 C111 Ms. Ursula Schluter 21701 80th Avenue West #4 Edmonds, Washington 98020 GEOTECHNICAL REPORT, PROPOSED RESIDENCE AT LOTS 1 & 2, 75TH PLACE WEST, EDMONDS, WASHINGTON This report presents the results of our geotechnical reconnaissance and evaluation for your pro- posed residence on 75th Place West in Edmonds. The purpose of our work was to evaluate the site and provide recommendations to aid in foundation design for the proposed single-family resi- dence. Our work included a visit to the site to perform a reconnaissance and a review of existing subsurface information about the site contained in a geotechnical report by Earth Sciences, dated March 21, 1986. The property is located on the west side of 75th Place West in the Meadowdale area of Edmonds, Washington. The property measures approximately 97 feet by 190 feet and consists of two lots located about 200 feet north of the intersection of 75th Place West and 158th Street S.W. The legal description for the property is: lots 1 & 2, Block 28, Meadowdale Beach, Snohomish County, Washington. The lots are bordered on the east by 75th Place West and on the west by the Burlington Northern Railroad right-of-way. The property is shown on the Site Plan, Figure 1. An occupied lot lies to the south of the subject property and a lot with an abandoned house and shed lies to the north. Portions of the abandoned structures which lie on the lot to the north protrude into the subject property. The ground surface is covered with dense brush and blackberry vines. The site slopes moderately downward from 75th Place West to the BNRR tracks. The average slope is about 1 vertical to 3 horizontal (1V to 3H). A retaining wall about 4 feet high has been Seattle • Everett • Fairbanks • Anchorage • St. Louis PRESIDENT: Earl A. Sibley, P.E. SR. VICE PRESIDENT: Atef A. Azzam; Raymond P. Miller, P.E.; Harvey W. Parker, P.E.; George Yamane, P.E. VICE PRESIDENT: Herman H. (Tex) Druebert, P.E.: Richard H. Gates, P.E.; W. Paul Grant, P.E.; Leland B. Jones, P.E.; Thomas E. Kirkland, P.E.; Gerry Millar, R.G.,; Frank W. Pita, P.E., P.G.; Ming•Jiun (Jim) Wu, P.E. CONSULTANT: William L. Shannon, P.E. Ms. Ursula Schluter March 29, 1990 Page 2 W-5385-01 built by the railroad along the toe of the slope. We understand this wall was constructed to prevent debris from sliding onto the railroad right-of-way. We understand that the proposed residence will be a multi -story, single-family house. We expect that a garage for off-street parking will also be constructed. The dimensions and locations for these structures are not known at this time. The results of the explorations presented in the report by Earth Sciences dated March 21, 1986, indicate that the site is generally underlain by 8 to 17 feet of slide debris consisting of loose sand, silt, and silty clay. Below the slide debris the soils consist of hard tan to blue -gray silt. The hard silt appears to be glacially consolidated. Considerable groundwater seepage was observed at the site during our reconnaissance. Groundwater flow was also noted on the test pit logs in the report by Earth Sciences. According to the report by Earth Sciences and a "Landslide Hazards Map" by Roger Lowe Associates, Inc., dated October 16, 1979, the property has been subjected to slope instability and sliding in the form of slumps of surface soils loosened by previous sliding. In our opinion, the existing fill and slide debris which covers the site would not provide suitable support for the proposed structures. We therefore recommend that the proposed structure be sup- ported on augercast concrete piles or drilled piers bearing in the hard silt which underlies the site. Augercast methods are preferred at this site because of the potential for caving in the loose soils. We expect that the bearing stratum will be located at depths ranging from about 8 to 17 feet and piles should penetrate at least 12 feet into the hard soil. The depth to bearing stratum for each pile should be determined during construction. SHANNON & WILSON. INC. Ms. Ursula Schluter March 29, 1990 Page 3 W-5385-01 For augercast piles or drilled piers we recommend a minimum diameter of 16-inches. In our opinion, 16-inch diameter augercast piles or drilled piers, with a minimum penetration of 12 feet into the hard silt would be capable of developing an allowable capacity of 20 tons each with an adequate factor of safety. We expect that settlement of properly installed piles or piers at this site would be negligible. In order to provide stiffness against potential soil creep, we recommend that the building founda- tions be tied together in the up -and -down -slope direction with a reinforced concrete grade beam. This beam should have moment connections with the tops of the piles. The piles and grade beam will form a stiff structural system to resist soil movement in the downslope direction. In order to increase the stability of the site we recommend that one or more trench subdrains be installed across the site in roughly a north -south direction. Subdrains would consist of slotted plastic pipe bedded in 3/8-inch pea gravel in the bottom of a sand -filled trench. The location of the trench subdrains will depend on design of the house, and should be determined after the layout of the house and floor grades have been established. We recommend that no additional fill be placed on the site, as the additional weight could reduce the stability of the site. Most of the soils excavated from trench subdrains or basement areas should be removed form the site. We should review any plans for placement of fill on this site so that unstable conditions are not created. Concrete Piles Augercast piles are installed by rotating a continuous -flight hollow -stem auger to a pre -determined depth. When the depth is reached, a high strength sand -cement grout is pumped, under controlled pressure, through the center of the shaft as the auger is slowly withdrawn. By maintaining pres- sure in the grout line and slowly extracting the auger no faster than an equivalent volume of grout is pumped, a continuous column of concrete is formed. A single large reinforcing rod can be installed for the full pile length through the hollow -stem of the auger, and/or a reinforcing cage can be placed in the column of wet grout. SHANNON & WILSON. INC Ms. Ursula Schluter March 29, 1990 Page 4 W-5385-01 The quality of auger -cast concrete piles is primarily dependent on the procedures and workmanship of the Contractor who installs them. A properly functioning pressure gage and pump stroke counter should be provided on the grout pump to assist in monitoring auger -cast pile installation. The counter is used to determine the approximate volume of grout pumped by counting the number of strokes of a displacement -type pump. The pump should, therefore, be calibrated prior to its use. The pressure gage is used to monitor the pressure of the grout to evaluate the rate at which the auger should be retracted, and if the auger or hoses are plugged. The auger should be withdrawn with slow positive rotation at a slow steady pull and should not be pulled until the grout has been pumped a few feet above the tip. Piers are constructed by drilling a hole with a short, single -flight auger. The auger is connected to a kelly bar which is rotated and lowered in and out of the borehole with a truck- or track -mounted drilling rig. When the hole has been advanced to the required penetration, all loose and disturbed soil at the bottom should be removed with a clean -out bucket which has the same diameter as the drilled borehole. Based on information from the exploratory test pits, it is our opinion that groundwater could be a problem during drilled pier installation at this site. Should caving occur in the loose silts and sands that are present at the site, casing would be needed in the upper portion as appropriate. After the pier has been cleaned and dewatered, reinforcing and concrete are placed in the hole. Reinforcing cages should have hole -centering guides. The concrete should have a slump of at least 6 inches and be placed in the borehole through a funnel or'elephant trunk' in order to prevent the free -falling concrete from hitting the borehole walls and contaminat- ing the concrete. Lateral Earth Pressures and Retaining Structures Basement level walls of the proposed structure should be designed for an equivalent fluid pressure of 55 pounds per cubic foot (pcf), plus one pound per cubic foot for each degree of upward incli- nation of the backslope above the wall. Cantilevered retaining walls which are not connected to the SHANNON & WILSON. INC. Ms. Ursula Schluter March 29, 1990 Page 5 W-5385-01 house could be designed for an equivalent fluid pressure of 35 pcf, plus one pound per cubic foot for each degree of upward inclination of the backslope above the wall. These pressures assume the walls are drained so that hydrostatic pressures cannot develop. Recommendations for wall drainage and backfilling are presented on Figure 3. Lateral forces would be resisted by passive earth pressure against the buried portions of structures and by friction against the bottom. In our opinion, passive earth pressures in backfill could be estimated using an equivalent fluid pressure of 280 pounds per cubic foot (pcf) above the ground- water table and 140 pcf below the water table. These values assume that the structures extend at least 18 inches below the lowest adjacent grade, and the backfill around (below) the structure is a horizontally graded, compacted granular fill. We recommend that a coefficient of friction of 0.5 be used between cast -in -place concrete and soil for non -pile supported structures. Base friction should not be considered beneath pile supported portions of the structure. Because of the large amount of groundwater seepage at this site, development should include the installation of trench subdrains to lower the groundwater level and improve the stability of the site. We expect that one or more trench subdrains will be required, extending approxi- mately north -south across the property near the east property line and again at about the mid point of the property. Depending on the layout of the structure, the footing drains along a day- light basement may function as one or more of the required subdrains. The locations and depths of the subdrains should be evaluated once the locations of the structures are known. A typical trench subdrain installation is shown on Figure 2, and a footing subdrain is shown on Figure 3. The subdrains should consist of slotted plastic pipe surrounded by at least 8 inches of drainage sand and gravel at the bottom of a trench filled with drainage sand and gravel, gradation specifications are presented on Figure 2. Native site soils do not meet the requirements for drainage sand and gravel. SHANNON & WILSON, INC. Ms. Ursula Schluter March 29, 1990 Page 6 W-5385-01 The trench subdrains should extend at least 5 feet below the existing ground surface and at least to the elevation of any proposed excavation level. It should drain south to the property line and, if possible, should be connected with a tightline to the existing storm water drainage sys- tem which runs up and down the slope near the south property line. Caving of the sides of the trench is likely during installation of the trench subdrain. Installation should begin at the south end and proceed up -slope. It may be necessary to periodically stop work for a day or two to let the site drain before advancing the trench. Footing drains consisting of 4-inch (minimum) diameter slotted plastic pipe should be installed on the upslope side of all retaining or basement walls. Freely draining sand or sand and gravel should be used as backfill adjacent to walls. Wall drainage and backfill recommendations are presented on Figure 3. The downspout water from the structure should be conveyed to a suitable discharge point, such as the existing storm drainage system, in a tightline. Subsurface drainage and downspout water should not flow onto the ground surface and should not flow into perforated footing drains. N`. WATTT =Virt 47 • The soils at the site are generally moisture sensitive, and will become soft and difficult to work when wet. It would be most advisable to schedule earthwork during the dry weather months. Pile or pier installation and any other earthwork should not be accomplished during periods of heavy rainfall. If fill is to be placed in wet weather or under wet conditions when control of soil moisture content is not possible, the fill should contain no more than 5 percent material passing the No. 200 mesh sieve, by weight, based on the minus 3/4 inch fraction. In addition: a.) Earthwork should be accomplished in small sections and carried through to completion to minimize exposure to wet weather. If there is to be traffic over the exposed subgrade, the sub - grade should be protected with a compacted layer of clean sand and gravel or crushed rock. SHANNON & WILSON. INC Ms. Ursula Schluter March 29, 1990 Page 7 W-5385-01 b.) No soil should be left uncompacted so it can absorb water. Soils which become too wet for compaction should be removed and replaced with clean granular material; and, c.) Excavation and placement of fill should be observed on a full time basis by a person expe- rienced in wet weather earthwork to determine that all unsuitable materials are removed and suitable compaction and site drainage is achieved. We recommend that these recommendations for wet weather earthwork be included in the con- tract specifications. Construction Monitoring and Plans Review We recommend that we be retained to work with your architect to design the necessary drainage installations at the site and to review the portions of the plans and specifications which pertain to earthwork and foundations to determine if they are consistent with our recommendations. We also recommend that we be retained to monitor earthwork construction, including drainage and drilled pier or augercast pile installations, to determine that the work is accomplished in a suitable manner. The installation of concrete piles or drilled piers should be monitored on a full time basis. This monitoring should include verifying the depth of competent bearing soil and measurement of the volume of grout placed into each pile. PRI&INAIN-11-M&I The conclusions and recommendations presented in this report are based on site conditions as they presently exist and the subsurface conditions are not significantly different from those indicated in the test pit explorations performed by Earth Sciences or inferred from our site reconnaissance. If during construction, subsurface conditions different from those encountered in the explorations and site reconnaissance are observed or appear to be present, we should be advised at once so that we can review those conditions and reconsider our recommendations where necessary. If there is a substantial lapse of time between submission of our report and the start of work at the site, or if SHANNON & WILSON, INC. Ms. Ursula Schluter March 29, 1990 Page 8 W-5385-01 conditions have changed due to natural causes or construction operations at or near the site, it is recommended that this report be reviewed to determine the applicability of the conclusions and rec- ommendations considering the changed conditions and time lapse. This report was prepared for the use of the Owner or Engineer/Architect in the design of the struc- ture. No soil boring or test pit explorations have been accomplished for this study. Unanticipated conditions are commonly encountered and cannot be fully determined by merely per- forming a site reconnaissance, taking soil samples or making explorations. Such unexpected conditions frequently require that additional expenditures be made to achieve a properly constructed project. Some contingency fund is recommended to accommodate such potential extra costs. We appreciate your continued confidence in our firm, please call if you have any questions. Sincerely, SHANNON & WILSON, INC. :QN N. Bp •.� i . •'OF WASy/'•.•• Cj i I Ralph N. BoivQ Senior Associate Enclosures: Figures 1 - 3 SHANNON & WILSON. INC. A9 Z---.,C- 96.59 Tjo Mlm Id HISU ------------ ;.Z. N 09. 6 01 Nil L■ Approx 1 ft. On -site Soil Trench Excavation Drainage Sand and Gravel Washed 3/8" Pea Gravel (8" minimum above pipe, 12" on sides, 4" below) 6" Minimum Diameter Slotted Plastic Pipe Trench Bottom and Subdrain Pipe Sloped to Drain Specification for Drainage Sand and Gravel Not to Scale 0 1-1/2 100 3/4 90 to 100 1 /4 75 to 100 No. 8 65 to 92 No. 30 20 to 65 No. 50 5 to 20 No. 100 0 to 2 By Wet Sieving Slope To Drain Away From Structure Pavement or 8" Impervious Soil Clean granular backfill, (See note 1) Excavation Slope - (Contractor's responsibility) 8" Minimum cover of 3/8" pe gravel over pipe Subdrain Pipe 10 ► • • %lM Subdrain PiM 4" Minimum diameter ppfrated or slotted plastic pipe; tight joints; sloped to drain (6"/100' Min.); Provide cleanouts. Basement or Retaining Wall Damp Proofing Washed 3/8" Pea Gravel or clean sand and gravel Weep Holes Floor Slab ►. Vapor Barrier 6" Min. 1. Wall backfill should consist of freely draining granular soil with no more than 5% (by weight based on the minus 3/4-inch portion) passing the No. 200 sieve(by wet sieving), with no plastic fines. 2. Backfill behind the wall should be compacted with hand - operated equipment. Heavy equipment should not be used as such equipment operated near the wall could Increase lateral earth pressures and possibly damage he wall. 3. Backfill should be placed in layers not exceeding 6" loose thickness, and should be densely compacted. Beneath paved areas, compact to at least 95% of the Modified Proctor maximum dry density (ASTM: D1557-70,). Otherwise compact to 92 % compaction. Ursula Schluter Residence Edmonds, Washington TYPICAL FOUNDATION SUBDRAIN AND BACKFILL March 1990 W-5385-01 SHANNON &.WILSON, INC. 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