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REVIEWED PLN BLD2020-0865+Geotechnical_Report+8.19.2020_1.22.39_PMa s s o c i a t e d earth sciences I i1 C ti Ip 0 9% t e d March 19, 2019 Project No. 190101E001 Vector One, LLC P.O. Box 13377 Everett, Washington 98206 Attention: Mr. Carl Clapp Mr. Matt Bolin Subject: Geotechnical Report Update and Geotechnical Plan Review 83XX Olympic View Drive Edmonds, Washington EXPIR CATION# BLD2018-1030 (NEW) PERMIT# 19-1025 BLD2020-0865 RECEIVED Sep 14 2020 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Reference: "Geotechnical Engineering Study, Proposed 3-Lot Short Plat, 8364 Olympic View Drive, Edmonds, Washington," prepared for Mr. Bill Ritter by Liu and Associates, Inc., dated September 26, 2005 (LAI Job No. SA112). Dear Mr. Clapp and Mr. Bolin: In accordance with your request, this letter serves as an update to the September 2005 Geotechnical Engineering Study prepared by Liu and Associates, Inc. (LAI). Our work has been completed for the exclusive use of Vector One, LLC, and their agents, in accordance with generally accepted geotechnical engineering practice. No other warranty, express or implied, is made. INTRODUCTION The subject site consists of two adjoining, undeveloped parcels totaling 0.65 acres located in the 8300 block of Olympic View Drive in Edmonds, Washington (Snohomish County Parcel Nos. 27041800109-200 and 27041800109-300). The location of the site is shown on the "Vicinity Map," Figure 1. It is our understanding that current plans include construction of single-family homes on each of the two lots. At the time of the 2005 Geotechnical Engineering Study by LAI, the site consisted of a single parcel with an existing home which has since been subdivided into three lots. One of the three lots, which contained the existing home, has since been sold and the project site now only includes the remaining two undeveloped lots. Subsurface exploration completed by LAI for their 2005 study included six test pits excavated to depths ranging from approximately 8 to 10 feet. Review of the test pit logs included in the Kirkland Office 1 911 Fifth Avenue I Kirkland, WA 98033 P 1 425.827.7701 Mount Vernon Office 1 508 S. Second Street, Suite 1011 Mount Vernon, WA 98273 P 1 425.827.7701 Tacoma Office 1 1552 Commerce Street, Suite 102 1 Tacoma, WA 98402 P 1 253.722.2992 i - www.aesgeo.com --' � -- --� 83XX Olympic View Drive Geotechnical Report Update Edmonds, Washington and Geotechnical Plan Review LAI report indicate that sediments encountered in the test pits generally consisted of a surficial topsoil horizon underlain by natural sediments interpreted to consist of Vashon advance outwash. This is consistent with regional geologic mapping. Groundwater seepage was not encountered in any of the test pits. Copies of the exploration pit logs are included in Appendix A. A site plan included in the LAI report showing the approximate locations of the test pits are also included in Appendix A. The City of Edmonds has requested that an addendum report be prepared to address specific plans for the two new residences and development standards for geologic hazard areas as specified in Sections 23.80.060 and 23.80.070 of the Edmonds Municipal Code (EMC). Currently, building plans are only available for the western parcel. This parcel is shown on the civil plans as "Lot A." SITE VISIT We visited the site on March 7, 2019. At the time of our visit, the site conditions generally appeared similar to the conditions described in the 2005 LAI report. The site remains vegetated by mixed coniferous/deciduous forest with moderately thick brush (Photos 1 and 2). No geomorphic evidence of recent or historical landslide activity was observed on the slope during our visit. Photo 1. View looking south-southeast toward Lot A from Olympic View Drive. March 19, 2019 ASSOCIATED EARTH SCIENCES, INC. TJP11d - 190101EO01-2 -Projects 1201901011KEI WP Page 2 83XX Olympic View Drive Geotechnical Report Update Edmonds, Washington and Geotechnical Plan Review Photo 2. View looking east-southeast toward Lot B from Olympic View Drive. REPORT REVIEW Upon completion of our review of the 2005 LAI report, we offer the following comments and recommendations. Geologic Hazards Slope inclinations on the western lot (Lot A) range from approximately 30 to SS percent over a total height of approximately 40 feet. Slope inclinations on the eastern lot (Lot B) range from approximately 25 to 55 percent over a height of approximately 28 feet. Section 23.80.20(B) of the Edmonds Municipal Code (EMC) states that slopes with inclinations of 40 percent or steeper over a height exceeding 10 feet classify as Landslide Hazard Areas. This includes most of the area of Lot A, including much of the proposed building area, and portions of the area of Lot B. Review of Natural Resources Conservation Service (NRCS) soil mapping of the area indicates that the soils underlying the site classify as Alderwood sandy gravelly loam, 15 to 30 percent slopes. As previously discussed actual slope inclinations at the site exceed 30 percent. Given the soil type and slope inclinations present, the site classifies as an Erosion Hazard Area under the EMC. March 19, 2019 ASSOCIATED EARTH SCIENCES, INC. TJP/1d-190101EO01-2 - Projects`20190101`KEJWP Page 3 83XX Olympic View Drive Geotechnical Report Update Edmonds, Washington and Geotechnical Plan Review Development in Landslide and Erosion Hazard Areas is allowed under the EMC provided that development standards specified in Sections 23.80.060 and 23.80.070 are met. Recommendations for mitigation of erosion hazards are provided in the LAI report. Provided that these recommendations are properly followed, it is our opinion erosion hazards for the project can be suitably mitigated. As required under Section 23.80.070 of the EMC, clearing and grading for the project is only allowed from May 1st and October 1st. The LAI report recommends a building setback of at least 20 feet from any portion of the site with an inclination equal to or exceeding 40 percent. This is not practical given the extent of steep (>40 percent) slopes at the site. Section 23.80.070 states that development in Landslide Hazard Areas is allowed provided that the development standards specified in the code are met. Section 23.80.070(4)(a) of the code specifies that the proposed development shall not decrease the factor of safety for landslide occurrences below the limits of 1.5 for static conditions and 1.2 for dynamic conditions. This section of the code appears to have been revised since the time of the 2005 LAI study, which did not include a slope stability analysis. In order to assess whether factors of safety on the slope exceed the minimum required under the code, an analysis of the slope was conducted using the computer program Slope/W, version 7.23 by GeoSlope International. The program used the Morgenstern -Price method for evaluating a rotational failure. Input parameters for the analysis included slope geometry, geology, and soil strength parameters. The slope geometry used for our analysis was based on topography depicted on Figure 2 along section line A -A. This section extends through the building area proposed for Lot A. In general, the topography on Lot A is steeper and higher than that on Lot B and therefore provides a conservative assessment of slope stability for both lots. For our analysis, the geology of the slope was based on the subsurface conditions shown on the exploration logs for test pits TP-4 and TP-5 (Appendix A). Analysis of the stability of the slope was completed for both the existing and post -construction cases. For the post -construction case, a surcharge load of 500 pounds per square foot (psf) was applied over the footprint of the house to simulate the building foundation loads. Soil strength parameters used for our analysis were selected based on the descriptions of the sediments provided on the exploration logs, published data, and our experience with similar sediment types. For evaluation of slope stability under dynamic conditions, a horizontal ground acceleration of 0.26g was used for our analysis. This value is equivalent to %2 of the peak horizontal ground acceleration based on a seismic event with a 2-percent probability of exceedance in 50 years. The stability of a slope can be expressed in terms of its factor of safety. The factor of safety of a slope is the ratio between the forces that resist sliding to the forces that drive sliding. For example, a factor of safety of 1.0 would indicate a slope where the driving forces and the resisting forces are exactly equal. Increasing factor of safety values greater than 1.0 indicate March 19, 2019 ASSOCIATED EARTH SCIENCES, INC. TJP/Id- 190101 E001-2 - Projects1201901011 KEJWP Page 4 83XX Olympic View Drive Geotechnical Report Update Edmonds, Washington and Geotechnical Plan Review increased stability. Factors of safety below 1.0 indicate conditions where the driving forces exceed the resisting forces and landsliding is imminent. The results of our analysis indicate that minimum factors of safety for the static and dynamic (seismic) cases exceed the minimum specified in the City's development standards for both the pre -development (existing) and post -development (proposed) cases. The results of the slope stability analysis are summarized below in Table 1. Copies of the Slope/W profiles depicting the stratigraphy, slope geometry, and soil strength parameters used in our analysis are included in Appendix B. Table 1 Summary of Slope Stability Analysis Results Case Calculated Minimum Factor of Safety Minimum Factor of Safety Per Code Pre -Development, Static 2.20 1.5 Pre -Development, Dynamic 1.28 1.2 Post -Development Static 2.05 1.5 Post -Development Dynamic 1.38 1.2 City development standards also require that point discharges from surface water facilities and roof drains will not discharge onto or upstream from a Landslide or Erosion Hazard Area. Review of the civil plans indicate that stormwater to be collected from Lot A will be discharged to the municipal storm drain system from a detention facility to be located below the proposed driveway. As previously discussed, no building or drainage plans were available for Lot B at the time of our study. Debris Wall The slope stability analysis completed for this study assessed the global stability of the slope. One of the more common types of landslides in the Puget Lowland are localized, shallow debris flow failures within the near -surface, weathered soil horizon. In order to mitigate the risk of damage due to this type of failure, the LAI report recommended that the upslope foundation wall of the building be constructed as a "debris wall" that extends at least 3 feet above the adjacent ground surface. We agree with this recommendation; however, the LAI report does not provide a recommended impact load for design of the debris wall. We recommend that the debris wall be designed to withstand an impact load of 500 pounds per lineal foot. The recommended impact load is based on a debris flow with a mass of 115 pounds per cubic foot (pcf), 3 feet deep, and traveling at a velocity of 7 feet per second. It must be understood that estimating the depth and speed of a debris flow is not an exact science. The structural engineer should note that no factors of safety were applied in our calculations; rather, we expect that the designer will apply an appropriate factor of safety to such a scenario. Our assumptions were based on our understanding of the subsurface conditions at the site, and the height and March 19, 2019 ASSOCIATED EARTH SCIENCES, INC. TJP/Id - 190101EO01-2 -Projects 1201901011KEIWP Page 5 83XX Olympic View Drive Geotechnical Report Update Edmonds, Washington and Geotechnical Plan Review inclination of the slope above the proposed structure. Future debris flows, if they occur, may vary from those estimated. Retaining Wall Design Parameters Lateral Earth Pressures The LAI report recommended that retaining walls designed for active (yielding) conditions be designed using an equivalent fluid pressure of 35 pcf for level wall backslope conditions and 55 pcf for inclined wall backslope conditions. The LAI report recommended that fully -restrained walls should be designed for at -rest earth pressure conditions using an equivalent fluid pressure of 45 pcf for level backslope conditions and 70 pcf for inclined backslope conditions. We recommend that wall backslope conditions not exceed a maximum inclination of 50 percent. Wall Drainage The recommended lateral earth pressures assume that drained conditions are maintained behind all retaining walls. It is imperative that proper drainage be provided so that hydrostatic pressures do not develop against the walls. This would involve installation of a minimum 1-foot-wide blanket drain to within 1 foot of finish grade over the full wall height using imported, washed gravel against the walls. The washed gravel blanket drain should be continuous with the footing drain recommended in the LAI report. Water collected in all wall and footing drains should be routed to a suitable point of discharge through one or more tightline pipes that are separate from the roof downspout tightlines. Passive Resistance and Friction Coefficient The LAI report recommends that foundation walls be designed to resist lateral deflection using a passive equivalent fluid of 300 pcf and basement walls and other retaining walls be designed using a passive equivalent fluid of 350 pcf. The LAI report also recommends a base friction coefficient of 0.60. No factor of safety has been applied to these values. We recommend the following allowable passive equivalent fluid and friction coefficient values: Passive Equivalent Fluid: 250 pcf Friction Coefficient: 0.30 The above -recommended allowable values include a factor of safety of at least 1.5. The recommended allowable passive equivalent fluid is suitable for use in design of foundation walls, basement wall, and other types of retaining walls. March 19, 2019 ASSOCIATED EARTH SCIENCES, INC. TJP/Id- 190101 E001-2 - Projects1201901011 KEJWP Page 6 83XX Olympic View Drive Geotechnical Report Update Edmonds, Washington and Geotechnical Plan Review Seismic Surcharge Pressure As required by the 2015 International Building Code (IBC), retaining wall design should include a seismic surcharge pressure in addition to the equivalent fluid pressures presented above. We recommend a seismic surcharge pressure of 10H and 11H psf where H is the wall height in feet for the active and at -rest loading conditions, respectively. The seismic surcharge should be modeled as a rectangular distribution with the resultant applied at the midpoint of the wall. Debris Wall As previously discussed, we recommend that the debris wall be designed to withstand an impact load of 500 pounds per lineal foot. This is in addition to the above recommended static wall pressures. Foundations The LAI report recommends the following allowable foundation bearing pressures: • 2,000 psf for footings founded on structural fill. • 2,500 psf for footings founded on medium dense advance outwash sediments. • 3,000 psf for footings founded on very dense lodgement till or very dense/hard transitional beds. Because neither lodgement till or transitional beds were encountered in the explorations advanced at the site, we do not recommend use of the 3,000 psf foundation bearing pressure for this project. Conclusion With the exception of the comments listed above, it is our opinion that the remainder of the recommendations provided in the LAI report remain unchanged. G EOTECH N ICAL PLAN REVIEW We have completed our geotechnical review of the following plans for the home to be constructed on Lot A: • Building plans consisting of Sheets 1 through 7, prepared by Emerald Home Design, dated October 10, 2018. March 19, 2019 ASSOCIATED EARTH SCIENCES, INC. TJP/Id - 1901OIE001-2 - Projects 120190101 JKEJ WP Page 7 83XX Olympic View Drive Geotechnical Report Update Edmonds, Washington and Geotechnical Plan Review • Civil plans consisting of Sheets 1 through 8, dated October 11, 2016; Sheet 1 of 1 titled "Site Plan," dated July 20, 2018 and Sheet 1 of 1 titled "SWPPP/TESC," dated July 20, 2018, prepared by Omega Engineering, Inc. The July 2018 civil plan sheets appear to replace Sheets 2, 3, and 5 in the 2016 version of the civil plans. Upon completion of our review we offer the following comments: • The retaining wall details in the building plans do not include the recommended drainage as discussed above in the "Retaining Wall Design Parameters" section of this letter. � Sheet 6 of the building plans state that a lateral seismic load of 7H was used for retaining wall design (no units given). We recommend that the designer either verify that this value complies with the recommended seismic surcharge pressures of 10H psf (active earth pressure conditions) or 11H psf (at -rest earth pressure conditions) recommended in the "Retaining Wall Design Parameters" section of this letter, or revise the plans to comply with these recommended values. • The "General Foundation Notes" in Detail 4 on Sheet 6 of the building plans indicate that an equivalent fluid pressure of 35 pcf was used for the basement wall design. This value is intended for use under active (yielding) earth pressure and horizontal backslope conditions. Inclined backslope conditions are anticipated on the back (south) side of the proposed house. We recommend that the equivalent fluid pressure recommended in the "Retaining Wall Design Parameters" section of this letter for inclined backslope conditions be used where this condition exists. • The basement wall on the rear (south) side of the house should be designed as a debris wall as recommended in the LAI report, and as discussed in the "Retaining Wall Design Parameters" section of this letter. Provided that the above -recommended changes are made to the project plans, it is our opinion that the plans reflect the recommendations presented in the LAI report as modified in accordance with the recommendations presented in this letter. March 19, 2019 ASSOCIATED EARTH SCIENCES, INC. TJP/ld-190101 E001-2 -Projects 120190101 J KEJ WP Page 8 83XX Olympic View Drive Geotechnical Report Update Edmonds, Washington and Geotechnical Plan Review We appreciate this opportunity to have been of service to you with your project. Should you have any questions, or require additional information, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington kA t it ott"ilJ J. Timothy J. Peter, L. E.G., L. Hg. Senior Engineering Geologist / 0 Matthew A. Miller, P.E. Principal Geotechnical Engineer Attachments: Figure 1. Vicinity Map Figure 2. Site and Exploration Plan Appendix A. LAI Exploration Logs Appendix B. Slope/W Profiles Note: Black and white reproduction of this color original may reduce its effectiveness and lead to incorrect interpretation. March 19, 2019 ASSOCIATED EARTH SCIENCES, INC. TJP11d- 190101 E001 -2 - Projects `201901011KEIWP Rage 9 0_ w E;D.:MQ II DATA SOURCES / REFERENCES: USGS: 73 SERIES TOPOGRAPHIC MAPS, ESRI/1-CUBED/NATIONAL GEOGRAPHIC SOCIETY 2013 SNOHOMISH CO: STREETS, CITY LIMITS, PARCELS, 2/19 LOCATIONS AND DISTANCES SHOWN ARE APPROXIMATE N 0 1000 2000 FEET VICINITY MAP 4U" OLYMPIC VIEW DRIVE SHORT PLAT NOTE: BLACK AND WHITE REPRODUCTION OF THIS COLOR E D M O N D S, WAS H I N G TO N ORIGINAL MAY REDUCE ITS EFFECTIVENESS AND LEAD TO PROJ NO. DATE: FIGURE: INCORRECT INTERPRETATION 190101 E001 3/19 1 LEGEND: 0 TP TEST PIT - LIU AND ASSOCIATES - 9/24/05 SITE BOUNDARY PROPOSED HOUSE G:i .14LET PROixC'fitJN ;€l'P) I PER SM. DE s. E1, 3, SEI I SHUT T i .'.» �fz ~� ti I• I r�ity FA °F3i ' TO PROitr'' LciTRAC �"O TO INS .TA! -,. .£}�•-a,tE• TREES •?a'Ii-�• ., .. .: i �r � - � � - � � STBIUZED, Cowto cTION ,.c _t lXi!ulili�i EXTE LA!R 1 " EN RAt 1 _ DIr ' ^ 3J S ETG CONTOUR INTERVAL 2a • '! rI� ::••jj ?' , i.! 1 A 1`w '^YMt �•� a �. 3 r r...... S , St SIcD. 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Y� '' ��'`-'•c`a_ �' k .. �jf- Y !�~, r' fi .45 / , . / � . .• / Y� ) ; ` J J 1 C13" J.�+ .. -..w ' TREE 'TO REM", '`�'~I' l.. 1 � r+..'' ••" Y.•\ i k .• r~ a. \ .1- � r >$.y "�k% . ! •n { / .: �' ! 1 i L` SEE TREE \ . ��, Vq •c. rf ...•.'/O � '' •� �'l ;^`^J T • f' 1 ....:.. � � j• Jl it s f BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAY REDUCE ITS EFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION. • 1 4,J f a s s o c i a t e d earth sciences n c o r p c r a t e d A SITE AND EXPLORATION PLAN o is so OLYMPIC VIEW DRIVE SHORT PLAT FEET EDMONDS, WASHINGTON PROJ NO. DATE: FIGURE: 190101EO01 1 3/19 2 APPENDIX A LAI Exploration Logs 1• _ 1 tr!• r -1 J 1 AA .- - 274 2 T&7/ IL .� ' - 'ram r' i 1 ✓ w / rr' j//♦`••_._ ��.r ` Ile .LV/\ -may 1\j / ' ri 2,56 • —r ' l.. 1 r_10<288 � c90 j - • + � 292 L r - 294 256..- / i� + + 1. ' rl 0"319 11 � l ��• J Ile MPG 1 • r f �O r f ' l .• 1 I - I ~ y-••~r- ✓ -J1_tip � , s ; • ti• a _• K i ►..._� —riff- ::� .) .� : 1 SITE AND EXPLORATION LOCATION PLAN LIU & ASSOCIATES, INC. - 3 LOT SHORT PLAT 8364 OLYMPIC VIEW DRIVE Geotechnical Engineering • Engineering Geology • Earth science E D M O N D S, WAS H I N G TO N JOB NO. 5A112 1 DATE 9/23/2005 PLATE 2 UNIFIED SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS GROUP GROUP NAME SYMBOL GRAVEL CLEAN GIN WELL -GRADED GRAVEL, FINE TO COARSE GRAVEL COARSE- MORE THAN 50% OF GRAVEL GP POORLY -GRADED GRAVEL GRAVEL WITH GM SILTY GRAVEL GRAINED COARSE FRACTION SOILS RETAINED ON NO. 4 SIEVE FINES GC CLAYEY GRAVEL SAND CLEAN SIN WELL -GRADED SAND, FINE TO COARSE SAND MORE THAN 50% MORE THAN 50% OF SAND S P POORLY -GRADED SAND SAND WITH SM SILTY SAND RETAINED ON THE COARSE FRACTION NO. 200 SIEVE PASSING NO. 4 SIEVE FINES SC CLAYEY SAND FINE- SILT AND CLAY INORGANIC ML SILT CL CLAY GRAINED LIQUID LIMIT ORGANIC OL ORGANIC SILT, ORGANIC CLAY SOILS LESS THAN 50% MORE THAN 50% SILTY AND CLAY INORGANIC MH SILT OF HIGH PLASTICITY, ELASTIC SILT CH CLAY OF HIGH PLASTICITY, FAT CLAY PASSING ON THE LIQUID LIMIT ORGANIC OH ORGANIC SILT, ORGANIC SILT NO. 200 SIEVE 50% OR MORE HIGHLY ORGANIC SOILS PT PEAT AND OTHER HIGHLY ORGANIC SOILS NOTES: SOIL MOISTURE MODIFIERS: 1. FIELD CLASSIFICATION IS BASED ON VISUAL EXAMINATION DRY - ABSENCE OF MOISTURE, DUSTY, DRY TO OF SOIL IN GENERAL ACCORDANCE WITH ASTM D2488-83. THE TOUCH 2. SOIL CLASSIFICATION USING LABORATORY TESTS IS BASED SLIGHTLY MOIST - TRACE MOISTURE, NOT DUSTY ON ASTM D2487-83. MOIST - DAMP, BUT NO VISIBLE WATER 3. DESCRIPTIONS OF SOIL DENSITY OR CONSISTENCY ARE VERY MOIST - VERY DAMP, MOISTURE FELT TO THE TOUCH BASED ON INTERPRETATION OF BLOW -COUNT DATA, VISUAL WET - VISIBLE FREE WATER OR SATURATED, APPEARANCE OF SOILS, AND/OR TEST DATA. USUALLY SOIL IS OBTAINED FROM BELOW WATER TABLE LIU & ASSOCIATES, INC. UNIFIED SOIL CLASSIFICATION SYSTEM Geotechnical Engineering - Engineering Geology Earth Science PLATE 3 TEST PIT NO. 1 Logged By: JSL Date: 9/6/2005 Ground El. 283.0' ± Depth USCS Sample W Other ft. CLASS. Soil Description No. % Test OL Brush and duff on surface Dark -brown, lose, organic, silty fine SAND, with fine roots, dry TOPSOIL 2 SM Light -brown, loose, silty fine SAND, trace gravel, dry 3 4 SP Brown -gray, medium -dense, gravelly, fine to medium SAND, dry to 5 slightly moist (fresh ADVANCE OUTWASH) 6 Gray, dense, fine to medium SAND, trace to some gravel, slightly SP moist (fresh ADVANCE OUTWASH) 7 8 9 Test pit terminated @ 9.0 ft, groundwater not encountered. 10 TEST PIT NO. 2 Logged By: JSL Date: 9/6/2005 Ground El. 297.0' ± Depth USCS Sample W Other ft. CLASS. Soil Description No. % Test OL Brush and duff on surface Dark -brown, lose, organic, silty fine SAND, with roots to 1-inch- diameter, dry (TOPSOIL) 2 SM Light -brown, loose, silty fine SAND, trace to some gravel, dry 3 4 5 SP 6 Brown -gray, medium -dense, gravelly, fine to medium SAND, occasional cobble, dry (fresh ADVANCE OUTWASH) 7 8 Light -brown, dense, gravelly, fine to coarse SAND, slightly moist SW 9 (fresh ADVANCE OUTWASH) 10 Test pit terminated @ 10.0 ft, groundwater not encountered. 11 LIU & ASSOCIATES, INC. Geotechnical Engineering - Engineering Geology • Earth Science TEST PIT LOGS 3-LOT SHORT PLAT 8364 OLYMPIC VIEW DRIVE EDMONDS, WASHINGTON JOB NO. 5A112 DATE 9124/05 PLATE 4 Logged By: JSL TEST PIT NO. Date: 9/6/2005 Ground El. 285.0' ± Depth USCS Sample W Other ft. CLASS. Soil Description No. % Test OL Brush and duff on surface 1 Dark -brown, lose, organic, silty fine SAND, with roots to 1-inch- diameter, dry (TOPSOIL) - F--I 2 SM Light -brown, loose to medium -dense, silty fine SAND, trace gravel, dry 3 Light -brown to gray, medium -dense, slightly silty, fine to medium SM/SP 4 SAND, trace to some gravel, slightly moist (fresh ADVANCE OUTWASH) 5 6 Light -gray, dense, fine to coarse SAND, trace to some gravel, SW 7 slightly moist (fresh ADVANCE OUTWASH) 8 9 Test pit terminated @ 9.0 ft, groundwater not encountered. 10 TEST PIT NO. 4 Logged By: JSL Date: 9/6/2005 Ground El. 291.0' ± Depth USCS Sample W Other ft. CLASS. Soil Description No. % Test OL Brush and duff on surface 1 Dark -brown, lose, organic, silty fine SAND, with roots to 2-inch- diameter, dry (TOPSOIL) 2 SM Light -brown, loose, silty fine SAND, trace gravel, dry 3 4 Light -brown to light -gray, medium -dense, fine to medium SAND, SIP trace gravel, slightly moist (fresh ADVANCE OUTWASH) 5 6 7 Light -gray, dense, fine to coarse SAND, trace to some gravel, SW slightly moist (fresh ADVANCE OUTWASH) 8 9 Test pit terminated @ 8.5 ft, groundwater not encountered. 10 j I __ - I __ .1 1 LIU & ASSOCIATES., INC. Geotechnical Engineering - Engineering Geology • Earth Science TEST PIT LOGS 3-LOT SHORT PLAT 8364 OLYMPIC VIEW DRIVE EDMONDS, WASHINGTON JOB NO. 5A112 DATE 9/24/05 PLATE 5 De ft. 1 2 3 4 5 6 7 8 9 10 11 TEST PIT NO. 5 Lopged Bv: JSL Date: 9/6/2005 Ground El. 272.6' ± )th USCS CLASS. Soil Description Sample No. W % OL Brush and duff on surface Dark -brown, lose, organic, silty fine SAND, with roots to 1.25-inch- diameter, dry (TOPSOIL) Light -brown, loose, silty fine SAND, trace gravel, and occasional SM boulder to 12 inches in size, dry Light -brown to light -gray, medium -dense, fine to medium, trace SP gravel, slightly moist (fresh ADVANCE OUTWASH) Light -gray, dense, fine to coarse SAND, trace to some gravel, SW slightly moist (fresh ADVANCE OUTWASH) Test pit terminated @ 10.0 ft, groundwater not encountered. utner Test TEST PIT NO. 6 Logged By: JSL Date: 9/6/2005 GroundEI. 277.5' f Depth USCS Sample W Other ft_ CLASS. Soil Description No. % Test OL Brush and duff on surface 1 Dark -brown, lose, organic, silty fine SAND, with roots to 1.5-inch- diameter, dry (TOPSOIL) 2 Light -brown, loose, silty fine SAND, trace gravel and occasional SM 3 boulder to 12 inches in size, dry 4 Light -brown to light -gray, medium -dense, fine to medium SAND, SP 5 trace to some gravel, slightly moist (fresh ADVANCE OUTWASH) 6 ------ Light -gray, dense to very -dense, fine to coarse SAND, trace to SW 7 some gravel, moist (fresh ADVANCE OUTWASH) 8 9 Test pit terminated @ 8.0 ft, groundwater not encountered. 10 2- LIU & ASSOCIATES, INCO Geotechnical Engineering - Engineering Geology • Earth Science TEST PIT LOGS 3-LOT SHORT PLAT 8364 OLYMPIC VIEW DRIVE EDMONDS, WASHINGTON JOB NO. 5A112 1 DATE 9/24/05 PLATE 6 APPENDIX B Slope/W Profiles Olympic View Drive Short Plat - 190101 E001 Pre -Construction Case Name: Weathered Vashon Advance Outwash Unit Weight: 115 pcf Cohesion: 100 psf Phi: 34 ° Name: Vashon Advance Outwash Unit Weight: 130 pcf Cohesion: 100 psf Phi: 37 ° 3 3 2 2 2 2 � O 2 2 > 2 N W 2 2 2 2 2 C CD 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 Distance (ft.) Olympic View Drive Short Plat - 190101 E001 Pre -Construction Case Static Conditions Name: Weathered Vashon Advance Outwash Unit Weight: 115 pcf Cohesion: 100 psf Phi: 34 ° Name: Vashon Advance Outwash Unit Weight: 130 pcf Cohesion: 100 psf Phi: 37 ° m Minimum Factor of Safety o C 0 M a� w ® 0 ® ® ® ® 0 0 0 i0 • 0 W 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 Distance (ft.) Olympic View Drive Short Plat - 190101 E001 Pre -Construction Case Seismic Conditions - 0.26g Name: Weathered Vashon Advance Outwash Unit Weight: 115 pcf Cohesion: 100 psf Phi: 34 ° Name: Vashon Advance Outwash Unit Weight: 130 pcf Cohesion: 100 psf Phi: 37 ° .a m Minimum Factor of Safety o • • • • • • • • • • 1.28 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 305 o inn • • • • • • • • • • • • Olympic View Drive Short Plat - 190101 E001 Post -Construction Case Name: � Unit We Cohesio Phi: 34 ` Name: Unit We Cohesio Phi: 37 ` C O M O W 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 Distance (ft.) Olympic View Drive Short Plat - 190101 E001 Post -Construction Case Static Conditions Name: Weathered Vashon Advance Outwash Unit Weight: 115 pcf Cohesion: 100 psf Phi: 34 ° Name: Vashon Advance Outwash Unit Weight: 130 pcf Cohesion: 100 psf Phi: 37 ° Z -v m Minims---- _�_ _r �_r_�__ CL • ® • • • e • • • • • • • • e e e • • • • • e e • s s • • s • • • • e • • • • • s e • • • • • • • • • • • • • • • • • • • s s • e • • • • ® • • • e e 305 :innrw e e e e e • • • • e ® • Olympic View Drive Short Plat - 190101 E001 Post -Construction Case Seismic Conditions - 0.26g Name: Weathered Vashon Advance Outwash Unit Weight: 115 pcf Cohesion: 100 psf Phi: 34 ° Name: Vashon Advance Outwash Unit Weight: 130 pcf Cohesion: 100 psf Phi: 37 ° Minimu • • • • • • . • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • . • • • • • • • • • • • z' 1.38