Loading...
18130 84TH AVE W.PDFIIIIIIIIIIIIII 15384 18130 84TH AVE W Dennis M.'Bruce, RE. M.S.C.E., M.B.A. Geotechnical/ Civil Engineer December 1, 1998 DEC 1998 City of Edmonds c/o McGrew & Michel, Designers 8022 - 212th Street S.W. Edmonds, Washington 98026 Subject: Geotechnical Addendum Building Permit Plan_Gheck_N_o._9_8_t372_,1 O'Leary Residence, � 18130 - 84th Avenue We_qt,1J'Edmonds This engineering letter responds to the City of Edmonds Plan Check Corrections list dated November 17, 1998 for the Dennis and Carla O'Leary residence (Plan Check No. 98-372). References: • Geotechnical report by D. Bruce, P.E. • Project plans by McGrew & Michel Backaround: This engineer is currently providing on -site geotechnical inspection services for the Michel Construction Inc., single family residence on Lot No. 2 (18132 - 84th Avenue West). Geotechnical conditions are in accordance with those anticipated by this engineer. This engineer has reviewed the project plans for the Dennis and Carla O'Leary residence, to be constructed on Lot No. 3 (easterly of the existing construction on Lot No. 2). This engineer has worked with project contractor to stake out the proposed building footprint. Geotechnical Review of Plans: This engineer has reviewed the specific plans for the Dennis and Carla O'Leary residence on Lot No. 3 (18130 - 84th Avenue West, Edmonds). The proposed residence layout is in accordance with the recommendations of this engineer's November 4, 1997 geotechnical report. It is understood that this engineer will provide on -site geotechnical inspections during the construction phase of this residence. SOILS - FOUNDATIONS - SITE DEVELOPMENT - INSPECTION - DRAINAGE - DESIGN & PERMIT - LEGAL P.O. Box 55502 - Shoreline, Washington 98155 - (206) 546-9217 - FAX 546-8442 McGrew -Michel Re: O'Leary Residence December 1, 1998 Pagei two Conclusions:. The proposed building plans for Lot No. 3, are aeotechnically approved subject to specific inspections by this engineer. If there are any questions, do not hesitate to call. M. WAS 17405 [-EXPIRES 12/23/ 1 4,4A�. M. a-o,� Dennis M. Bruce, P.E. Geotechnical / Civil Engineer Dennis M.. Bruc e*, P.E. M.S.C.E., M.B.A. Geotechnical/ Civil Engineer I—vir November 4, 1997 ,k"A[ TV Copy 1=111MI Mr. Dennis V. O'Leary NOV - 3 1998 Chief Financial Officer Lynnwood Mortgage Corporation 6505 - 218th Street S.W., Suite 9 Mountlake Terrace, Washington 98043 Subject: Geotechnical Evaluation Lots 2 and 3 Approximately 84th Place and 182nd Place, Edmonds, WA This engineering report presents the results of a geotechnical evaluation of the property at approximately 84th Place and 182nd Place, Edmonds, Washington. This evaluation was necessitated by. owner and developer concerns, as well as City of Edmonds requirements. REFERENCES: • Vicinity Map (figure 1) • Topographic Survey Map by Chadwick and Winters, of Lots 2 and 3 dated October, 1997 • Site photographs (available) BACKGROUND: It is understood that Lots 2 and 3 are part of an overall parcel containing Lot No. 1 with existing residence, and Lots 2, 3 and 4 (see Survey map and plot plans). This investigation deals with Lots 2 and 3 with regard to geotechnical slope issues. It is understood that property owner wishes to construct a single family residence on Lot 3 and another single family residence on Lot 2. No development or construction has occurred on either Lot 2 or 3 to date. Lots 2 and 3 contain a "flatter" portion, as well as a more steeply sloped rear (southerly portion). The flatter portions of the lots currently consist of lawn grasses, with a few mature trees. The steeper (southerly) portion of the lots are densely vegetated with shrubs, bushes and trees (see photographs), SOILS - FOUNDATIONS - SITE DEVELOPMENT - INSPECTION - DRAINAGE - DESIGN & PERMIT - LEGAL 17814 8th Ave. N.W. - Shoreline, Washington 98177 - (206) 546-9217 - FAX 546-8442 Attachment 6 Mr' * Dennis V. O'Leary Page two ASSESSMENT: While not within the scope of this evaluation, this engineer assessed the existing residence on Lot 1 for any geotechnical distress. No evidence of any foundation settlements or shifting were observed. Visual assessments of Lots 2 and 3 by this engineer throughout the past year revealed no evidence of any geotechnical distress: No sliding, no creep, no shifting, nor any significant erosional degradation was observed on the overall property, including Lots 2 and 3. In order to augment existing site geotechnical information, soil test pits were dug (by backhoe) under this engineer's observation on August 9, 1997, See soil test pit logs (attached). The findings of the four soil test pits (plotted on the Survey Topographic Map) were very similar. Namely: dense brown, silty sand to approximately three (3) to four (4) foot depths. Dense to very dense grayish brown weathered glacial till (hardpan). No ground water was present in any of the four soil test pits. All test pit walls remained vertical and stable throughout the excavated time frame (approximately two hours). CONCLUSIONS/RECOMMENDATIONS: Based on the findings of this investigation, and experience with similar sites in the area, Lots 2 and 3 are geotechnically approved for the proposed single family residences, subject to the following conditions: Standard reinforced continuous and spread footings. Allowable bearing pressure: 2,000 p-s-1- Equivalent fluid pressure of 35 p.c.f. is recommended for any retaining wall provided the drainage zone is inspected and verified by this engineer. For retaining wall design, use a friction factor of 0.55 and passive pressure of 350 p.c.f. The foundations for the proposed StFUCtures may be placed anywhere on Lots 2 and 3, outside of the dashed top -of -bank survey area (see Topographic map). In other words, there are no geotechnical limitations to the proximity of the proposed residences and the top -of -slope line. (It is geotechnically Mr. Dennis V. O'Leary Page three possible, but not likely, to property construct a foundation on the steeper portions of Lots 2 and 3. This would require uneconomic stabilizing techniques and methods). To be clear, the geotechnical set -back distance to the top -of -bank dashed line is zero. It is understood that political or zoning set -back distances do apply per City of Edmonds requirements. It is important to restate, however, that no set- back distance is essential for geotechnical reasons. It desired, exceptions or variances could be pursued. Geotechnical inspection by this engineer prior to any foundation concrete placement. The proposed structures 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 minimum widths of eighteen (18) 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 over excavated hole, the width of the overexcavation at the bottom must be at least as wide as the sum of two times the depth of the overexcavation and 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 three thousand (3,000) pounds per square foot (p.s.f.). 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 of the foundation must be level structural fill, We Mr. Dennis V. O'Leary Page four recommend the following design values be used for the foundation's resistance to lateral loading: Parameter Coefficient of Friction Passive Earth Pressure Where: Design Value 0.55 350 p.c.f. (1) p.c.f. 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 with minimum overlaps of 12 inches for sealing purposes. 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: Paramete Active Earth Pressure* Passive Earth Pressure Coefficient of Friction Soil Unit Weight Desicin Value 30 p.c.f. 350 p.c.f. 0.55 125 p.c.f. Mr.' Dennis V. O'Leary Page five Where: (1) p.c.f. is pounds per cubic foot (2) Active and passive earth pressures are 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 p.s.f. should be added to the active equivalent fluid pressure). 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 effects 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. 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 the additional lateral pressures resulting from the equipment. Placement and compaction of ret . aining wall backfill 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. Due to their high silt content, if the native soils are used as backfill, a drainage. composite, such as Mirafi and Enkadrain, should be placed against the retaining walls. The drainage composites should be hydraulically connected to the foundation drain system. the purpose of these backfill requirements is to assure that the design criteria for the retaining wall as not exceeded because of a build-up of hydrostatic pressure behind the wall. The subsection entitled General Earthwork and Structural Fill contains Mr. Dennis V. O'Leary Page six reco ' mmendations regarding placement and compaction of structural fill behind retaining and foundation walls. EXCAVATION AND SLOPES: In no case should excavation, slopes be greater than the limits specified in local, state and national government safety regulations. Temporary cuts up to a height of four (4) feet deep in unsaturated soils may be vertical. 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. Under specific recommendations by the geotechnical engineer, excavation cuts may be modified for site conditions. 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. 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: Footing drains are recommended at the base of all footings and retaining walls. These drains should be surrounded by at least six (6) inches of one -inch -minus washed rockwrapped 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 in any of the test pits during the field work. Seepage into the planned excavation 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 excavation 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 any area where foundations, slabs, or pavements are to be constructed. Any exposed slopes to 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 building is paved. Mr.'Dennis V. O'Leary Page seven GENERAL EARTHWORK AND STRUCTURAL FILL: The proposed building and pavement areas should 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. NOTE: Specific clearing limits to be established at pre -construction meeting with City of Edmonds building officials and inspectors. Structural fill is defined as any fill placed under the building, behind permanent retaining or foundation walls, or in other areas where the underlying soils needs 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: Location of Fill Placement ' Beneath footings, slabs or walkways Behind retaining walls Beneath pavements .Minimum Relative Compaction 95% 90% 95% for upper 12 inches of subgrade, 90% below that level Where: Minimum relative compaction is the ratio, expressed in percentages, of the compacted dry density to the maximum dry density, as determined in accordance with ASTM Test Designation D-1557-78 (Modified Proctor). Mr. Dennis V. O'Leary Page eight Use of On -Site Soils If grading activities take place during wet weather, or when the silty, on -site soils are wet, site preparation costs may be higher because of delays due to rains and the potential need to import granular fill. The on -site soils are generally silty and thus are moisture sensitive. Grading operations will be difficult when the moisture content of these soils exceeds the optimum moisture content. Moisture se ' nsitive soils will also be susceptible to excessive softening and "pumping" from construction equipment traffic when the moisture content is greater than the optimum moisture content. Ideally, structural fill which is to be placed in wet weather should consist of a granular soil having no more than five (5) percent silt or clay particles. The percentage of particles passing the No. 200 sieve should be measured from that portion of the soil passing the three -quarter -inch sieve. The use of "some" on -site soils for fill material may be acceptable if the upper organic materials is segregated and moisture contents are monitored by engineering inspection. DRAINAGE CONTROLS: No drainage problems were evident on Lots 2 and 3. Surface runoff flows generally westerly (from the flatter portions of the lots). This engineer recommends compliance with the City of Edmonds standard storm water drainage controls. The surficial sandy soils are such that it is practical to utilize an infiltration storm water system. CONCRETE: All foundation concrete (footings, stem walls, slabs, any retaining walls, etc.) shall have a minimum cement content of 5-1/2 sacks per cubic yard of concrete mix. INSPECTION: The recommendations of this report are only valid when key geotechnical aspects are inspected by this engineer during construction: • Soil cuts • Foundation subgrade verification Mr. ' Dennis V. O'Leary Page nine • Any retaining wall, or rockery placement • Any fill placement and compaction • Subsurface drainage installation SUMMARY: The two proposed single family residences (on Lots 2 and 3) are geotechnically viable when constructed in accordance with the recommendations herein, compliance with City of Edmonds approved plans and key geotechnical inspection during construction. There are no geotechnical constraints limiting the proximity of the proposed residences to any sloped portion of the property. As a practical measure, this engineer recommends the residences be situated no further southerly than the dashed top -of -slope line. If desired, however, it is geotechnically feasible to construct the residences beyond (more southerly) than the dashed survey line. GEOTECHNICAL REVIEW OF PLANS: Prior to the City of Edmonds issuing a building permit, this engineer should review the specific house plans for compliance with the recommendations of this geotechnical report. 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 const ' ruction 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:vIb Dennis M. Bruce, P.E. Geotechnical/Civil Engineer 17405 [MIRES -IMY (V( 2j -T-T irk / BRACK.— IAI / . � . Pl G51t IEL NAI MAPLE 23 Lwfom OIL IL WY MARSH Fa� TY , Lou EIPAVM c� PA a- ..... ..... BEACH Pk I R 26 LLA CMLA E 00 es BROWNS BA Y 7 FREU PIL CotwTy PARK OTH PL SW 5 y I OVERM, PK it] tj 1. IT r is Im. 9- 18STH if-. '4 wrr PL SW IRK 187TH I 40 K Sw I Sm v R T I T SW S r.HFRR U 11 R 9600 ;Sob Itts, S, sr 2 t; !2 19211D Sw 1967 w 'LOOY LN DR awo L w HILL ST --- ---- 'T vISIA IWIM 51 SW p 6300 SIER 202110 I GLEN ST YWA 24 PI IST RIOW ST ELL LS"W -1-- S, ST Ar- ST J ST YOST Im'" Pl. MV"IAL Sw Lo' PARK V Sr 5 '011 IL si'i; jE 7TH ST 111. PL % A, z 30"; Sw ell 40- ?SAY B if ?w giv p NNW I ..' tt not ........... j ".'r .1 7 WAR 1 — rs. yN. mR 1; WIP MTII-5?� IONK ............. N:1 WIN-, . . . . . . . . . . . 1- 1/1Y 13 o; 55 jl.i A% A W, nU 6 rz� Mill "' R-4 PS 9 Tr Vim, z tv co co co UA z cr. C) % N 87043'02" E 72.31' 1)5:g T OW i, I till 0 66 Zi' " E� 0,'45 65 kttachment 4 SEE NOTI N 87*43'02" E 72.31 cc IID SEE NOTI -Z 00 l .00 io 145 ---65 -------- -IS CEIVED DEC 0 1997 "P Attachment 5 OZO. ov ) I".Z- . Civi�� C�,nier CITY OF EDMONDS X, RECORD OF SHORT SUBQIVISION �=g 140 C) �0_ 14-21 IV -ON L= V-4 OD This is to certify that the properties'as shbwn on the attached map (Exhibit "A") and described as follows: See Exhibit "B" have been divided under the provisions of the Edmonds Subdivision Ordinance (Sec.12.10) File No.— S-28-79 subject to the following conditions and requirements: 1. Exhibit "C" Hold Harmless Agreement 2. Underground wiring to be provided in accordance with Ordinance #1387 with building permits. 3. Connection to city water and sanitary sewer system required with building permits. 4. Excavation and grading shall conform to the requirements outlined in Chapter 70 of the Uniform Building Code with building permits. 5. Turn around required on all lots with building permits. ALL REQUIREMENTS MUST BE MET AND ALL IMPROVEMENTS MUST BE INSTALLED PRIOR TO ISSUANCE OF BUILDING PERMITS. I/we certify that I/we are the legal owner(s) of the property described above. I/we warrant that all representations are true and correct and understand that in the event of any misrepresentation or failure to comply with the conditions and regulations set forth herein, the City of Edmonds shall have the right to declare the subdivision void and record a statement to that effect in the Grantor -Grantee's Index in the office of I- L e Sno"LQiLLs1bg,,opnLy allUILor. — �0 CA t SIGNED 0 A T,� SGN C T, OD'] 0�111RV DATED this day of X 19 STATE OF WASHINGTON COUNTY OF SNQHOMISH� ss: On this day prsonally appeared before me and 4- 4141 L�l z to me known to be the individ/ua in and who execut:d the Ahin and foregoing instrument, and acknowl . 'edged that ls described signed the same as free and voluntary act and deed, for the uses and purposes i�4�e r i n mentioned. v 19 n dnd6T iny'.hand and official seal this d a y o f r J Notary Public in and for the State of Washingt( residing ati kttach" m—e-ilt-1 k03100,161 VOL V02 PAGE- 48 FILE NO. S-28-79 EXHIBIT "C11 Owners, and all persons having any present or subsequent Ownership interest in these lands, and the successors and assigns of owners Or other parties having any said interest, hereby agree that the City of Edmonds shall be held in all respects harmless from any and all claims for damages for in- junctive relief which may be occasioned now or in the future to adjacent land or improvements by reason of the construction, operation and maintenance of the drainarre system and hereby wa ive and release the City of Edmonds from -any and all claims for damages, excluding damage caused solely by an act or Omission of said City and injunctive relief which the owners, or their successors or assigns, may themselves have now or in the future by reason of the construction, maintenance and operation of said drainage system. CD AUTI-TORIZED F 0111, ' CIr C 'T "'%J0NDS cz) Cr.: By, P a Of J__ VOL P02PAGE 49 r 11/18/1998 MICHEL CONST PAGE 03 if. 09.28 7785086 FINDINGS OF FACT AND CONCLUSIONS A. Site Description 1. Site.Development And Zoning: Domis O'Lmry File No, V-91-145 Fage 3 of 7 a) F2ck- (1) Size: ne subject property is approximately 17,952 square feet (set Attachment 7). (2) Land Usa 'no subject PTOPeTty i& undeveloped and vacant. (3) Joing: 71e subject property is located in a Single -Family Residential (RS- 12) zone (see Atachment I)- j4) Terrain apd Vegetation,: 'The statp slope critical area is located in the southern portion of the property. it contains dense vegetation. shrubs, blackberry and trees. The northrrn portion bas, a moderate tire with fewer trees and the ground is covered by gra3s, 2. Neighboring Development And Zoning: (1) Fact. Thr properties to the north. south, east and west are zoned Single -Family Residential (RS-12) and either vacant or are developed with single-family homes (see Attach,ment 1). B. State Environmental Policy Act (SEPA) 1. L-jZ: Variances granted based on special circumstances arc exempt from SEPA review OVAC 197-11-800(6)(b) and ECDC 20.15A.080). C. Edmonds Community Development Code (ECDC) Compliance 1. CritiCal'Areas Compliance a', Facts: (1) This propoEal is subject to review undrr J�CDC Chapter 20.15.13 (CriticAl Areas Otdinance). (2) The applicant has submitted a Cri6caj Areas Checklist (CA-97-236) and it was determined that a study was required, h� Conclusion: The survey and top of slope deteunination dated October 1097 was done by Robert Winters P.L.S. of Chadw;ek and Winters, A geotechricQl report dated %kwember 4, 1997 was performed by Dennir Bruce, P.& It supports the request to construct within the cAtical ares buiJding setback and buffer. 2. Compliance with RS-12 Zoning Standards (1) Fact, The short plat (S-28-79) declared this propertY a flag lot, Current policy in regardg to flag lot ietbacks ii to consider all setbacks as ��� (2) Conclusion: Tbc structure as proposed will comply with the requirements of the RS- 12 Loning standards. I I f�.l I N rT%ft I A , ­1 , ­_ � .- __ 11/18/1998 09;28 7789086 MICHEL CONST PAGE 04 FLAG LOT DETERMINIATIO14 FINDING OF FACT FOR THE: Thomas Berry, four lot subdivision at 8432 Olnoic View Drive Lot 2 It is our determination that the front yard of this property shall be to the rortheast , that the rear yard shall be to the south and�that the sideyards thall be to the east and west for the following reasons; see attached nap, 1) Conforms with topography on site, 2) allows for adequate open space between homes, 3) provide 'idequate separation from easement. This action is subject to 15 day appeal, commencing on August 9_, 1979 If no appeal is received within this time period, this determination becomes effective on the 16th day or, August 24, 1979. Prepared by- N.R. Luster Date-, 8-9-79