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Gcutcchnical I:ncinccrim_ Itoport <br /> I lousing Flopc <br /> Qecember 5, 200d <br /> Rh!I filcNo.2170-i <br /> Pagc G <br /> Infiltration Ratcs <br /> We identificd I soil type on the site, 6veret! grnvelly, sandy loam. The SCS lists this suil as a <br /> 'Cypc 13 soil, suitablc for infiltration. Thc soil survey of Snohomish County lists thc sourcc as <br /> glacial terrnces ouhvash plains. The uutwash soils we found in our e�cavat�ons we class�iL as <br /> loamy sand. Based on the SCS Textural "Criangle and our visual examination of the soils �ce <br /> recommended that an infiltration rate of2.dl inches per hour be used for soils classified as line to <br /> medium SAND wi[h sil[ or silty fine ta mcdium SAND. At your request we had sieve ai .lyscs <br /> run on ttivo samples below G Ceet obtained from the test pits. i'rom the resul[s we interpretcd a <br /> final design long-tenn infiltration rate of 3?8 inches per hour. Thiti is the figure you should use. <br /> 1'he till soils are uot suitablc lor infiltration. <br /> CONCLUSIONS r\Nll RCCOM�1ENllAT[ONS <br /> Gencral <br /> II is our opinion, fron .t geotechnical standpoint, that the site is compatible �vith the planned <br /> developmenL Our explorations �.vithin [he site indicate that advance outwash sands underlic thc <br /> sitc. These soils should provide adequate support for [he planned stn�cture. Medium dense or <br /> better soils should typically be encountered about 0.2 [0 4.0 feet below [he existing surface. We <br /> recommend that stn�cture be designed utilizing shallow foundations. Foo[ings should estend <br /> Nirough the topsoil, fill, loose,surficial soils and bc foimded on the medium dense or better nativc <br /> soils or s[ructural filL llic advance uu[�vash sands shuuld be suitable for the planned on-site <br /> infiltration sWctures. <br /> The soils likely to be espuseJ during construc[ion ure sli�h[h to moderatcly moisWre-sensiticc <br /> and may soften whcn we[. Wc rccommend [ha[ construction takc p�ace during the drier summer <br /> months, Flowever, if construc[ion [akes place during Ihe wet season, additional espenses and <br /> delays may bc c�p«ted due to the wet cunditions. Additional expenses could include [he export <br /> of on-site soil, the import of cl�an, granular soil for (ill, and the need to place a blanket of rock <br /> spalls in tlie access roads, construction traffic areus, and paved areas prior to placing strucW�al <br /> filL The on-site soils may be used as structural fill provided they can be compacted to plan <br /> specitications. R�vll shnidd bc re[ained to detcrminc if the on-site soils can be used during <br /> construction. <br /> R1V11 ASSOCIA7ES, LTD. <br /> / <br />