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7.28.2013-liu & assoc-geo-lambrecht.pdfGeolvVlnieaf Engineer4-o Mr. Stott Schr1>✓ber Ronscott Construction 761 Datt:v Street. Edmonds, WA 98020 Dear Mr. Sc rieber: Eminentring Geology SutJect; Additional In -Situ Infiltration Test. T....a brecht Short Plat 9441 Olympic View Drive Edmonds. Washington L&A Job No. 11-061 INTRDI)UCTION Earth uc3:er?ce We previously completed an in-sRu infiltration test inn the north side of the subject project site wrtii the test result and our recommended infiltration nate for the design of infiltration trenches presented in our 04f 1<` 013 report. At your request', we also conducted an in - situ infiltration test on the south side of the site r,vilh the test result and our recorrrmended infiltration rate for the. design of the in.filtrution trendies to be construeted on the south r side of the site presented in this report. TEST PIT LOCATION Al OIL CONDITION The location of the infiltration test; on the south side of the site.. IT-2, is shown can 111atc 21 attached hereto. The test pit imcountere-1 about 10react of topsoil. underlain by a layer of` broix—tt, slightly silty. fine sand, about l.9 feet thick. `this soil layer was underlain to th} 19213 Kenlake Place NE a Kenmore, Washington 9 028 Phone () 483-91 ° Fax (5)486-2746 u1r, 28.2013 Lam Brecht :short Flat L A ,lob No. 11-061 Page 2 bottom of the test pit by a fresh advance ottti- ash d`posit of light-brw-vn. dense.. tine to niodium sand with trace; gravel. Ground-v ater 'WaS not encountered by the test pit. INFILTRATION 'TEST PROCEDURE `1"f-ie in -situ infiltration test w -- conducted can the �Quth side of the site was carried out in accordance with the procedure € utlired in Washin 4on State Department of Ecology 2005. tarn titer Managgpient Manual for�ngt.c?zx. First. a p .t. about. 10 feet. by 10 feet by 2.0 feet deep was excavated out at. the test location. !% smaller pit about 4.25 feet by 4.5 beet. b- about 2.0 feet deep was thcta excavated out in. the n-riddle of the larger pit:. The inner smaller pit was Measured for its bottom dimensions', then filled with water for hours until the amount of water infiltrating in io bottom of the pit reached a steady state (i.e.., the volume of water infiltrating into ifiel,ground through bottom t f the pit. was the sane as volume of water discharged into the bit while water in the pit remained at a constant level) for at bast arc hour. Clear tap wate' was used in the test. The infiltration rate into bottorn of the inner smaller pit was then determined by the constant head method. with the volume of water discharged into the pit € iseasured with a ilow meter attached to the lose conveying water from the lancet into the pit for a period of 30 ridnutes. Over, the elapsed time of 30 minutes tbcc floe meter i-neas fed 8 gallons (ar 10.4 cubic feet.) of -ovater being discharged into the pit. This converts. to, with a botton, area of the pit at M 125 square feet, ara infiltration rate of 13.1 iph (111ches per boor). LIU & ASSOCIATES, INC. July 29, 2013) F_ambrecht Short Plat L&A Job No. ! l-(lbl Pap-c 3 CONCLUSION ION AND RECOMMENDATIONS The infiltration rate of the advance oumash sand deposit underlying, The north side of the site � as determined to be 10.3 ip. h. Based on .a correction factor of 4. the design in:fltration rage of (lie advance outkvash sand deposit should be ?,.5 1 iph. We reconirnend a deli-n infiltration mate not to exceed � � iph lac t�si~d i.rt design of the infiltration trenches to be constructed can the north side of the site for on -site stortmwater disposal. 1-he infiltration rate determined by the in -site, infiltration test on. the south side of the site was 13.1 ipla ivh i ch is grenter than the infiltration rate determined by the previous in -situ infilvation test on the north side. Therefore, our recommended infiltration ra e of'?.5 iph f«t the design of the infiltration trencltr s should still be applicable for the infiltration trenches to be constructed on th(! south side of the ,site. The remaining reconu-nendations in our 911112011 geotechnical report should still be complied with for: the construction of all infiltr ition trenches. LIMITATIONS This report has been prepared for the specific appli ation to this pro ect for die exclusive use bv Ron cost Construction and its ass.ociativs. representative--,, consultzuits and contractors. The conclusions and interpretations in this report, hoNvever, should not be construed as a warrant:V of the subsurface conditions. 'llie scope of this report does not include services related to construction safety° precautions and our recommendations are not intended to direst the contractor's methods. techniques, sequences or procedures, except as specifically described in this report fior design consid rations,. L] & ASSOCIATES, Lambrecht Short Plat L&A Job N c). 11-061 Pkqc 4 Our conclusion and reconunendations are based on the geologic and soil conditions I encountered in the test pits txcavated on the site, our experi.unce Lind enLlineermcl judgment and the infiltration test. results. The ot mclusions and recounuend-ations are professional opinions deriVed in a manner consistent. with the level of care and sk-111 ordinarih, e-x-crcised by other members of the pmfession currently practicing under simikir conditions in this area. No warranty, e\pressed or implied, is inadc. The tactual .subsurface conditions of the site nlay vary from those encountered by the test pit, The nature and extent of such variations may not. become evident until construction starts. If variations appear then, we should be retahicd to re-evaluate the recommendations of this report, and to verify or modif;v- them in w6ting prior to procceding Further with the construction of the proposed dtvOopmeat, C1,0SURE We are pleased to be of sen ice to you on this project. Please feel free to Contact us if you have any questions regarding this report or ncc4 further consultation. Yours very truly, L M SOCI4-11:;', INC. J. S, (Julian) Liu, Ph.D., P1, Consultina Gcotmhnical EngineeT FIxe '2 attached, off nq'. JV lor e; SITE AND EXPLORATION LOCATION PLAN! IU & ASSOCIATES, INC. LAMBRECHT SHORT PLAT 9441 OLYMPIC VIEW DRIVE ao�Fii�at �.�Ftz�eer�n • Etsgtnring GeZ3oY Ea.;V) acifinca EDMOD, WASHINGTON c Q • • � � C9 q'1 �s rh C3 r,y t7 Cox. G t� gn Zo U 5 n r. LL O i3 Ld IL OL LO LL 0 Q z a.. a� 0 .a i e� �z 4 ASSOCIATES, INC. Geotechrzical Engineetsrr rlg.nearinq Gealogy Forth SuenL-- July,- 25, -20 13 Mr, Scott Scltricber Ronscott Con tructiOn / 61 Dalev Street Edmonds. WA 98020 Dear fir. Schrieber: Sut>juet: Design Infiltration Rate Lambrecht Short: Plat 9441 Olympic View Drive Edmonds. Washinutan L&A Job No, 11- 61 Additional Test Pits and Soil SU�Mples Pre ionsl,, soil partie-le distribution analysis tests had been conducted on two soil samples obtained from the advance outxvash deposit underlying the north sick` of the site, with the test results presented. iMour M1112011 geotechnival report. We also conducted one in -situ infiltration test on the north side of the site, evith the results presented in our 04,11 2/2013 report. Atthe request of Cite of Edmonds, two test pits Nvere excavated can July 11, 2013, on the south side of the subject project :site and one sail was obtained from the advance. outwash deposit from each of these U,,'-o test pits (see Plate '12 attached hereto.)_ The test pits xAvre excavated and the soil samples obtained by ethers without a representative from Liu 'T Associates on site. These tiv.,o samples, were sent to HN A labor aor€° for Particle.Size Distribution tests. The test results Mere used to deter zinc whither the desien infiltration Washington, if Phone y. 4• <; July 2,5- 2013 Lanibrecht Short Plat L&A Job No, 11-061 page 2, rate we rccommended for the same advance ouavash deposits on the north side of thy; as presented in our 4.02/20.13 report, can, also be used to design the infittration trenches to be constructed on the south side of the sitc% Comparison of Test Results -Ile particle size distribution test results of Samples 3 and 4 obtained from the south side of the site are presented on P lateA-1 and A-2 attached hereto. The percentages of clay, silt and sand/gTavel of the two. north side soil sampits (&m.iples 1 &2) and two south. side sarnples (Samples 3 & 4). detennined froin the particle size distribution tests, are listed and compared on th c table, below.: Sample Test Depth % % % D10 USDA No, Pit No. feet. Clav Silt San&'Gravel Size Classification 1 1 5.0 - 0 3.9 5.8 90.3 0,0786 Sand 2 4_5 - 557 4.9 4,1 91.0 0. 0 8211 4 Sand 3 5.5 — 6.5 19 15.5 913 0.014 Loamy Sand 4 4 5,5 — 6.5 2,4 9,2 88A 0,046 Sand llie test results of Sample No. 4 appear to be approximately comparable to those of S,%nplc Nos, I and 2 obtained. from the north side of the site. However, the silt content of Sample No. 3 is higher than and its D10 size is lower than those of the north side szzmples. This is likely because this sample was contaminated with the more silty. soil layer ov-c-rlying. the advance autwaili deposit duringsampling, LILT & ASSOCIATES, INC. July IS- 2013 Lambreclit Short Plat I -&A Job No, 1] -061 Page 3) Recommendations As presented on our 04/021,20 13 in -situ infiltration test report, the infiltration rate of the advance ouhvasb deposit ,)n tile north. side was determined to be 10.33 iph (inclies per hour) and, -with a correction. factor of 4, its design infiltration rate was detenuined to be 2.57 iph,. We recormitended in our 002/2013 report that a design infiltration rate of 2.5 iph be used for design of infiltration trenches on the north side. Although we have reasons to believe the less hworable- paiiiele distribution test. results Of Soil &1n)Ple- 3 Avas due to soil wnt-amination by more silvy, Soil during sampling,. wt recon-unend that on the conservative side a design infiltration rite of 1.25 1ph be used for the design of the infiltration trenches to be constructed on the south side of the site, Please Feel firee to contact tj s i.f you have questions. Yours very truly, L I ASSOCIPX��,S, INC. 1. S. (julian) Liu, Pli,D., P-E. Consulting Geotechnical Engineer Attach- Plates 2, A- I and A-1 LIU & ASSOCIATES, INC.