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22816 102ND PL W.PDFiiiiiiiiiiiiii 15 5 8A 22816 102ND PL W CITY COPY Dennis M. Bruce, RE. M.S.C.E., M.B.A. Geotechnical/Civil Engineer pit. ber 6', 1993 Mr. Rob Michel 22937 Highway 99 Edmonds, WA 98026 RECEIVED. Subject: Geotechnical Assessment - Westgate 3 Lots z - q_? - 3 0 0 E'C 13 1993 ENGINEEfiING This engineering report presents the results of a geotechnical assessment of the property as shown on figure 1. The property is approximately rectangular (nominally 350 ft. by 130 ft.) and has never been developed. This geotechnical assessment was performed to provide more specific criteria for the proposed three single-family residences and access road development. References: • Preliminary Geotechnical Reconnaissance, dated November 23, 1992 by D. Bruce, P.E. • City. of Edmonds Planning Division Preliminary Review and Preliminary Approval and Conditions dated April. 19, 1993. • City of Edmonds Determination of Non -Significance (D.N.S.) pos . ted April 16, 1993. • City of Edmonds Final Review and Approval with Conditions dated May 11, 1993. • Project Design Plans by Michel Construction and Design, December 1993. • Site photographs (attached). Assessment The primary geotechnical issue impacting development of this property is s . ite topography (slopes). Geotechnical assessment of the site was performed by this engineer on November 19, 1992 using visual, photographic techniques, hand dug soil test pits, and experience with similar sites. The site has never been developed and is covered with brush, bushes, and trees varying in maturity. The lot contains slopes varying in steepness from 5 to 80 percent. A series of ten backhoe test pits were dug on Jun e 21, 1993 along the proposed access road to lots 2 and 3, the proposed residence locations, and the existing access road to lot 1. The test pits were du g under the direct observation of this engineer. It or/ '7"r # 9, The subsurface stratigraphy of all ten backhoe test pits was similar: lile -, o 0 to .7 ft.' Organics and dark brown loam. .7 to 2.0 ft. Medium dense sandy loam/well graded sands (SW) 2.0 to 7.0* ft. Dense free draining sands (SW) with occasional gravels. *Note: test pits #1, #5,'#9 were dug to ten foot. depths." The remaining seven test pits were dug to depths varying between six and eight feet. SOILS - FOUNDATIONS - SITE DEVELOPMENT - INSPECTION - DRAINAGE - DESIGN & PERMIT - LEGAL 17814 8th Ave. N.W. - Seattle, Washington 98177 - (20�) 546-9217 Mr. Rob Michel Page Two No groundwater was encountered in any of the ten test pits. Conclusions/Recommendations The results of this investigation along with engineering analysis of the project design plans confirms the findings of the November 23rd preliminary reconnaissance. The site is geotechnically approved for the proposed 3-lot single*family residence with access drive subject to the following conditions: 0 Foundation allowable bearing pressure = 2,000 p.s.f. Equivalent fluid pressure of 40 p.c.f. is recommended for any basement level retaining wall design 1?rovided drainage zone is inspected and verified by this engineer. For retaining wall design, use friction factor of 0.55 and passive pressure of 350 p.c.f. The proposed structure can be supported on conventional continuous and spread footings bearing on undisturbed native soils or on structural fill placed above native soils. See the later sub -section entitled General Earthwork and Structural Fill for structural fill placement and compaction recommendations. Continuous and individual spread footings should have m inimum widths of eighteen 0 8) and twenty-four (24) inches,,respectively, and should be bottomed at least eighteen (18) inches below the lower adjacent finish ground surface. Depending on the final site grades, some overexcavation may be required below footings to expose competent native soils. Unless lean concrete is used to fill the overexcavated hole, the width of the.loverexcavation at the bottom must be at least as,� Wide as the sum of two times the depth of the overexcavation tand the footing width.,.' For example, an overexcavation extending two feet below the bottom of a three -foot -wide footing must be at least seven feet wide at the base of the excavation. Footings constructed according to the above recommendations may be designed for an allowable soil bearing pressure of two thousand (2,0.00) pounds per square' foot (psf).* A one-third increase in this design bearing pressure may be used when considering short- term wind or seismic loads. For the above design criteria, it is anticipated that total post - construction settlement of footings founded on competent, native soils (or on structural fill up to five (5) feet in thickness) will be about one-half inch, with differential settlements on the order of one -quarter inch. Lateral loads due to wind or seismic forces may be resisted by friction between the foundations and the bearing soils, or by passive earth pressure acting on the vertical, embedded portions of the foundations. For the latter condition, the foundations must either be poured directly against undisturbed soil or the backfill placed around the outside Mr. Rob.Michel Page Three of the foundation must be level structural fill. We recommend the following design values be used for the foundation's resistance to lateral loading: Coefficient of Friction 0.55 Passive Earth Pressure 350 pcf Where: (1) Pcf is pounds per cubic foot ' (2) Passive earth pressure is computed *using the equivalent fluid density. We recommend that a safety factor of at least 1.5 be used for design of the foundation's resistance to lateral loading. Slabs -On -Grade: Slab -on -grade floors may be supported on undisturbed, competent native soils or on structural fill. The slabs may be supported on the existing soils provided these soils can be recompacted prior to placement of the free -draining sand or gravel underneath the slab. This sand and -gravel layer should be a minimum of four (4) inches thick. We also recommend using a vapor barrier such as, 6-mil plastic membrane beneath the slab. Permanent Foundation and Retaining Walls: Retaining walls backfilled on one side only should be designed to resist lateral earth pressures imposed by the soils retained by these structures. The following recommended design parameters are for walls less than twelve (12) feet in height which restrain level backfill: Active Earth Pressure 40 pcf Passive Earth Pressure 350 pcf Coefficient of Friction 0.55 Soil Unit Weight 125 pcf Where: (1) Pcf is pounds per cubic foot (2) Active and passive earth pressures ate computed using equivalent fluid densities. For restrained walls which cannot deflect at least 0.002 times the wall height, a uniform lateral pressure of one hundred (100) psf should be added to the active equivalent fluid pressure. Mr. Rob Michel Page Four The values given above are to be used for design of permanent foundation and retaining walls only. An appropriate safety factor should be applied when designing the walls. We recommend using a safety factor of at least 1.5 for overturning and sliding. The above design values do not include the effect's of any hydrostatic pressures behind the walls and assume that no surcharge slopes or loads will be placed above the walls. If these conditions exist, then those pressures should be added to the above lateral pressures. Given the consistency of free draining sandy subgrade soils, hydrostatic build- up is unlikely, however. Also, if sloping backfill is desired behind the walls, then we will need to be given the wall dimensions and slope of the backfill in order to provide the appropriate design earth pressures. Heavy construction equipment should not be operated behind retaining and foundation walls within a distance equal to the height of the wall, unless the walls are designed for th e* additional lateral pressures resulting from the equipment. Placement and compaction of retaining wall backfi'll should be accomplished with hand -operated equipment. Retaining Wall Backfill Backfill placed within eighteen (18) inches of any retaining or foundation walls should be free -draining structural fill containing no organics. This backfill should contain no more than five (5) percent silt or clay particles and have no particles greater than four (4) inches in diameter. The percentage of particles passing the No. 4 sieve should be between twenty-five (25) and seventy (70) percent. The purpose of these backfill requirements is to assure that the design criteria for the retaining wall are not exceeded because of a build-up of hydrostatic pressure behind the wall. The top foot to eighteen inches of the backfill should consist of a relatively impermeable soil or topsoil, or the surface should be paved. The sub- section entitled General Earthwork and Structural Fill contains recommendations regarding placement and compaction of structural fill. behind retaining and foundation walls. Excavations and Slopes: In no case should excavation slopes be greater than the limits specified in loc . al, state, and national government safety regulations. Ar4E�m . iporary,catks�l to a-, beight of foqr, For temporary cuts having a height greater than four (4) feet, the cut should have an inclination no steeper than 1:1 (Horizontal:Vertical) from the top of the slope to the bottom of the excavation. All permanent cuts into native'soils should be inclined no steeper than 2:1 (H:V). Fill slopes should not exceed 1:1 (H:V). It is important to note that sands do cave suddenly, and without warning. The contractors should be made aware of this potential hazard. Mr. Rob Michel Page Five Water should not be allowed to flow uncontrolled over the top of any temporary or permanent slope. All permanently exposed slopes should be seeded with an appropriate species of vegetation to reduce erosion and improve stability of the surficial layer of soil. Drainage Considerations: We recommend the use of f0QtJ,ng drains at the base of all footings and retaining wwts� These drains should be surrounded by at least six (6) inches of one -inch -minus washed rock wrapped in non -woven geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar material). At the highest point, the perforated pipe invert should be at least as low as the bottom of the footing and it should be sloped for drainage. All roof and surface water drains must be kept separate from the foundation drain system. No groundwater was observed during our field work. However, seepage into the planned excavations/soil cuts is possible, and likely if excavation occurs during winter months, and if encountered should be drained away from the site by use of drainage ditches, perforated pipe, French drains, or by pumping from sumps interconnected by shallow connector trenches at the bottom of the excavation. The excavations and site should be graded so that surface water is directed off the site and away from the tops of slopes. Water should not be allowed to stand in ally area where foundations, slabs, or pavements are to be constructed. Any exposed slopes should be covered with plastic to minimize erosion. Final site grading in areas adjacent to buildings should be sloped at least two (2) percent away from the building, except where the area adjacent to the structures are paved. General Earthwork and Structural Fill: We recommend that the residence and access road be stripped and cleared of all surface vegetation, all organic matter, and other deleterious material. The stripped or removed materials should not be mixed with any materials to be used as structural fill. Structural fill is defined as any fill placed under the garage, behind permanent retaining or foundation walls, or in other areas where the' underlying soils need to support loads. This engineer should observe site conditions during and after excavation prior to placement of any structural fill. All structural fill should be placed in horizontal lifts with a moisture content at or near the optimum moisture content. The optimum moisture content is that moisture content which results in the greatest compacted dry density. The moisture content of fill soils is very important and must be closely controlled during the filling and compaction process. The allowable thickness'of the fill lift will depend on the material type, compaction equipment, and the number of passes made to compact the lift. In no case should the lifts exceed twelve (12) inches in loose thickness. The following table presents recommended relative compaction for structural fill: Mr. Rob Michel Page Seven Closure: The findings and recommendations of this report were prepared in accordance with generally accepted professional engineering principles and practice. No other warranty, either express or implied, is made. The conclusions are based on the results of the field exploration and interpolation of subsurface conditions between explored locations. If conditions are encountered during construction that appear to be different than those described in this report, this engineer should be notified to observe the situation and review and verify or modify the recommendations. If there are any questions, do not hesitate to call. DMB:njt Dennis M. Bruce, P.E. Geotechnical/Civil Engineer tiq-3 17405 I EMRES 12/23/1 -Yq-S� -1 Mr. Rob Michel Page Six Minimum Relative LQcatiQn Qf Fill Elacemeat Compaction Beneath footings, slabs or walkways Behind retaining walls 95% 90% Beneath pavements 95% for upper 12 inches of subgrade, 90% below that level Where: Minimum relative compaction is the ratio, expressed in percentages, of tile compacted dry density to the maximum dry density, as determined in accordance with ASTM Test Designation D-1557-78 (Modified Proctor). Rockeries The proposed access road to serve lots 2 and 3 requires soil cuts and fills. Rockeries are necessary to provide stabilization and erosion control. Based on preliminary review of access road sections, W&kpeyaheig :�hqq x., c. e e e ,yy pg4ev -! W- -V41- . Standard rockery designs and normal good practices are applicable to this site, subject to inspection. InsWction The recommendations of this report are only valid when key geotechnical aspects are inspected by this engineer during construction: • Soil cuts • Foundation subgrade verification • Rockery and drainage zone installation • Any fill placement • Subsurface drainage installation Summary The proposed Michel 3-lot development is geotechnically viable when constructed in accordance with the recommendations herein, compliance with City of Edmonds approved plans and requirements and key ge'otechnical inspection during construction. Statement of Minimal Risk The existing site geotechnical factors pose a minimal risk to this project. This project poses a minimal risk to neighboring residences if observed and inspected by this engineer. Mr. Rob Michel Page Seven Closure: The findings and recommendations of this report were prepared in accordance with generally accepted professional engineering principles and practice. No other warranty, either express or implied, is made. The conclusions are based on the results of the field exploration and interpolation of subsurface conditions between explored locations. If conditions are encountered during construction that appear to be different than those described in this report, this engineer should be notified to observe the situation and review and verify or modify the recommendations. If there are any questions, do not hesitate to call. DMB:njt I trR�s A., LF %-1 17405 Dennis M. Bruce, P.E. Geotechnical/Civil Engineer jq'13 I EXF4RES 12/2311 t 47S� I 10, 44 All. ZN- tai� A i M.S.C.E., M.B.A. Dennis M. Bruce, P.E. es . "'@v April 29, 1994 Geotechnical/Civil Engineer BUILDING City of Edmonds M A, 'Y 0 6 "19'9 4 Community Services Dept. 250 5th Avenue N. Edmonds, WA 98020 Subject: Special Geotechnical Inspection - Michel 3-Lot (S-93-30, ED 80) This engineering report presents the results of ongoing geotechnical inspection for the Michel 3-lot development near Highway 104 at 102nd Pl. S.W.. Inspection is required as a condition of the City of Edmonds approved plans and as agreed by project developer, Mr. Rob Michel. References: * Approved project plans 0 Representative construction photograph (attached) 0 Geotechnical Assessment by D. Bruce, P.E. dated Dec. 6, 1993 All key geotechnical aspects were (and are) inspected by this engineer including: slope stability Monitor excavation Road and foundation subgrade verification Rockery placement Fill material placement Erosion control Conclusion/Recommendations: As anticipated per the Geotechnical Assessment report, the subsurface material encountered during the road grading operation and individual residence foundation was dense, stable sands. (See photographs) • All slope cuts were monitored and performed well (stable). • Rockery construction was achieved using approved base rock embedment, drainage zone per approved plans, and well -linked, properly battered rock placement (see photos). • Rockery backfill was placed in compacted lifts resulting in a finished slope of I (V):2(H) or shallower. • All road fill placement was compacted with a vibratory plate compactor in lifts not exceeding 12 inches (loose). SOILS - FOUNDATIONS - SITE DEVELOPMENT - INSPECTION - DRAINAGE - DESIGN& PERMIT - LEGAL 17814 8th Ave. N.W. - Seattle, Washington 98177 - (206) 546-9217 City of Edmonds Page Two • Individual foundation subgrade, material was verified to meet or exceed 2,000 p.s.f. bearing capacity- • Throughout the construction phase, erosion control fencing was properly installed and maintained. Given the nature of the clean sandy soils, most if not all rainfall infiltrates rather than runs off the property- • Property line survey stakes and string lines were established and maintained by project surveyors. Thus, all work performed to date has been subjected to geotechnical inspection and been performed in accordance with approved plans and normal good practices. The work to date is geotechnically approved. If there are any questions, do not hesitate to call. DMB:njt V 17405 Emms 12/23/ Xt� & a'-� Dennis M. Bruce, P.E. Geotechnical/Civil Engineer A 'XJ' tq'ovk 10415 228th St SW Edmonds Wa. 98020 28 March 1994 Mr. Paul Mar Community Services Director City of Edmonds 4b 250 5th Ave. N. Edmonds, Wa. 98020 Re: S-93-30 Proposed 3 Lot Subdivision SIR 104 & 102nd Place W. Dear Mr. Mar, BUILDING. MAR 510 1994 I recently participated in the public hearing process concerning the above referenced project. I have attempted to follow up to see if the conditions set forth were being met. I do not believe that they are being met. My primary concern is that the Final Review condition for ECDC 19.05, Earth Subsidence and Landslide, have been waived by the Building Official. If I had known that the City's intention was to waive these requirements and that attaching condition were an eyewash, I would have appealed. I would have requested that ECDC 19.05 be mandatory as a minimum standard of care for development of this subdivision. I have some experiences and comments about the process I would like to share: 1. The Planning & Engineering Departments claimed that each other had authorization over this process. Low and behold, neither did, the Building Official does. A lack of coordination on this subject is very apparent. It took a heart-to-heart talk with Bob Alberts to discover that the - Engineering department has no interest in the subsurface conditions at all on private property and hence no authority. I feel I was subjected to a run around and that I may have made a nuisance of myself. If Gordy Hyde and Jim Bissell had been more forthcoming in disclosing that the Building Official had already waived the ECDC conditions they could have saved themselves a lot of questions. I apology, they were patient but incorrect in not clearly telling me that Ms. Graf had official waived ECDC 19.05. After Wendie's departure, Jim Bissell reluctantly took over. I do not feel Jim has had the time to understand my concerns about the sensitive area, steep slope & the tree preservation the way Wendie had. He admits to not being knowledgeable about the conditions to the short plat or previous discussions. Wendie's departure is a loss to this process. Page 2 March 28, 1994 2. 1 sense from discussion with the staff that ECDC 19.05 Ordinance isn't really applicable in areas outside "Meadowdale". I don't think the Ordinance was intended to be restricted to Meadowdale. Furthermore, the Ordinance identifies "areas with slopes greater than 15%" as being appropriate. I know other jurisdictions within our region with a similar ordinance which would make this ordinance mandatory for this soil type, sand, and this gradient, 50'vertical fall. 3. 1 sense from discussion with the staff that ECDC 19.05 Ordinance isn't applicable to "Engineedng Work" like retaining walls, utilities, and roadways but to house construction. I don't think the Ordinance was intended to be restricted to home building. -I fail to see this delineation in the. Ordinance.. . I knowthat many-slide-s-within our. region -are.caused by -this type of- - construction activity. Furthermore, I recognize that depositing fill on a steep hillside represents a potential hazard, risk. I hope the Engineering Department will be monitoring the roadbuilding, and utility activities and requiring the special inspector to submit wdtten reports on the excavation and backfilling and a retaining wall design. I recall being told that ECDC 19.05 isn't a Engineering Department requirement. I now agree bureaucratically speaking. However, better orchestration of the ECDC 19.05 requirements by all the departments is appropriate. 4. 1 sense from discussion with the staff a lack of review about "public safety" with regard to I steep slopes. In discussions, I recognized a shift in response from enforcement of the "codes" to reliance on the Engineer of Record. I think the peer review feature of ECDC 19-05 would give the staff and the neighbors a greater sense of confidence. I am very much interested in knowing if the decision to waive the ECDC 19.05 considered the concerns expressed by the neighbor's during the public hearing process, and sound professional consultation or just " shooting from the hip". Furthermore, I think a written explanation by the building Official is in order to clarify her position to the neighbors who took the time to participate in this process. i Any help you can render in resolving this issue will be appreciated. Very Truly Yours, Peter J. Jr. cc: B Alberts J. Graf R. Clave 0. Tollefson M. Pattison B. Helgen S. Dwyer PERMIT APPLICATION REQUIREMENTS To: Applicant STREET FILE From: Lyle Chrisman, Engineering Inspector Owner. Plan Check No: Address:—Zze5l IM04 III, Ki Date: After review of the subject permit application, the following requirements must be met: 1. Construction hours are: WEEKDAYS — 7:00 A-M.-10:00 P.r*LWEEICENDS/HOLEDAYS — 10:00 A.IVL-6:00 P.1VL 2. A separate RIGHT-OF-WAY CONSTRUCTION PERMIT is required for all work on public property. (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) 5.- NO WORK SHALL BE DONE WITHIN 15 FEET OF STREAMS OR 10 FEET FROM ANY CLOSED DRAINAGE FACILITY. BUILDER/OWNER IS RESPONSIBLE FOR IDENTIFYING CONDITIONS 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, TIGHTLINES AND CATCH BASIN INSTALLATION. INSPECTIONS ARE REQUIRED PRIOR TO BACKFILLING. (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%. Waiver granted to %. (ECDC 18.80.060D) 10. Driveways must be paved from property line to City RIGHT-OF-WAY. A separate permit 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. 'Mere is a separate charge for the water meter. (ECDC 7.20) 14. A back 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 separate permit is required. LID# Fees paid: Yes No Charge�_ (ECDC 18.10) etw1mou- Vlg�6J LAOT.' 17. Underground wiring is required ota I Tnewnpon�str4ucetion, and for additions, alterations, and repairs that excee� 50% of the total assessed value of the structure. (ECDC 18.90) 18. A FINAL ENGINEERING INSPECTION IS REQUIRED PRIOR TO THE BUILDING DIVISION GRANTING OCCUPANCY Aj OF THE BUILDING OR STRUCTURE. (ECDC 18.90) -T ILL S- ME PRMTREQRDOT '77P..�:ET FILE PLANNING DATA SITE ADDRESS:-2 'Sit -102m. FL. - LJ. DATE: ZONING: PERMIT#: PROJECT DESCRIPTION: SETBACKS: Reguired Setbacks: Front: Left Side:_JLRight Side:_&::��Rear: Actual Setbacks: Front: ,�5,g-;z"Left Side:-7'-g "Right Side: Rear: I�L-10 FLOOR AREA: LOT COVERAGE: Maximum Allowed:-4#0�z ctual: �2- BUILDING HEIGHT: Maximum Allowed: (9*') Actual Height: 3 -73-q2,Sp SUBDIVISION: CRITICAL AREAS #: T�2- � �z SEPA DETERMINATION: --Ws LOT AREA: / Z, 1p�5'Z- Y-1 A I I I , F Plan Review By:. i , P-Ap 00"'s