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Mike Vance � C <br /> April 9 2004 <br /> Pagc 2 <br /> SITE CONOITIONS <br /> SURFACE CONDITIONS <br /> T'hc property is a rcctangular lot locatcd on thc west side of Scahurst Avenue. Esisting residcnces arc <br /> located north and south of the site,and also do�mslopc on the southwest sidc. Thc site is partially Iocaled <br /> on a stecp slope dirccQy abuve a small,natural drainage fcawre that flows toward Glcnwood Avenuc. <br /> We performed aur geologic sitc reconnaissance an March I I, 2004. 'I�he slope directly west of thc <br /> residcncc is terraced and vegetated and has bccn landscaped wi�h plants, shrubs and trees. The terraccs <br /> are generally two fect high by thrce fect widc anJ conswcted of ntodular blocks and pieces of concretc <br /> slab. The ovcrall grade of thc slope including terracing is approximalcly 50 perccnt or 2H:1 V to the fence <br /> linc. IIclow thc fcncc linc, the slopc gradually b+rades to about 20 perccnt or approximately SH:1 V. The <br /> -------- -- <br /> slopc bclow the terracing is vcgctated primarily with blackbcrries and vine maple. We observed yard <br /> debris (primarily grass and trec cuttings) on thc lowcr, tlattcr slope arca oulside tFe fence line. Runoff <br /> from thc residcncc is tightlincd in a 3 ro 4-inch Pcxiblc pipe bcyond thc fence line. We did not obscrvc <br /> arcas of active sccpage on thc property or bclow the property linc on the westcrn slopc. Gxposcd surficial <br /> soils at thc sitc consist primarily of silry sand with variablc gravel contcnt. <br /> Thc topography of thc sitc includc< a north-south trcnding ridgelinc at the castem edgc of thc <br /> property where thc cxisting structure is located. Thc cicvation of the sitc is approximatcly +320 fcet <br /> (dawm: L'vcrett 7.5' Quadranglc, USGS rcviscd 1973)along Scahurst Avcnue. <br /> GEOLOGY <br /> l'he Pugct Sound basin is a rcgian of Quatcrnary (last 3 million ycars) scdiments that range in <br /> thickness bel�ecen 800 and 2400 fect. 'I'hc basin arca has been rcpcatedly overriddcn by Pleistocenc <br /> (bct�vicen I I,000 and 3 million ycars ago) continental glacial ice dcpositing lill, glacial sand and gravel, <br /> and glacially-formcd lakc clay and sil�. Thc rcpcatcJ glacial action has resul�cd in numcrous north-south <br /> trending ridgcs, aith intcrvcning vallcys tillcd with post-glacial alluvium and/or marinc dcpusits.� Thc <br /> most recent glacial cycic of seJiment deposits is rcfcrred to as the Vashon Drill, occurring betwccn <br /> 13,500 and I5,000 ycars ago. <br /> Our rcvicw of Ihc �Vashingtan Statc Dcparuncnt of Natural Resourccs gcologic map, Prcliminup� <br /> SraJicra! Geo(ogic A1np oj dic hlukrtr��o und la�erert Qi�nrlremg/ec, Snohonrish Counly, B�ns/iirtgton <br /> inJicatcs that surficial soils at thc sitc arc mappcd ;.s glacial till of thc Vashon Drilt. Glacial �ill typically <br /> consists of a hctcrogcncous mix�urc of sand, gravcl, cobblcs and occasional bouldcrs in a silt and clay <br /> matris Ihat was dcpositcd Ucncath a glacicr. 13ccausc glacial till has bccr ovcrriddcn by thousands of fcet <br /> of icc, it is ty��ically dcnsc to ��cry dense. Glacial till in thc Gvcrett area typically mantics hills, ridges, <br /> and slopcs and ��arics in thickncss Gom about 10 to GO fcct. <br /> A zonc of ���calhcrcd till typically overlies the dcnse glacial till to depths of 3 to 10 fect. This <br /> �vcathcred zonc is sumc��hat draincd, whcrcas thc um�'cathcrcd till is a barricr to vcrtical drainagc. Watcr <br /> � Gals�cr. Ricliard\V..Chairman,"Gnginccring Gcology in 11'ashington.Volmnc l:'\Vashingmn Sla�c Dcpartmcnt <br /> of Natural Rcsuurccs, I3ullctin 7S. 1959. <br /> (i e o li n g i n c c r s IIUIRa101-00 . ���� <br /> 'r <br />