6101 23RD DR W NORPRO 2016-01-01 MF Import

. � � , June 3. 201 I Project No.'P-657S 3.2 Soils In genernl, soil conditions at the si�r consisi of npproximalely 6 l0 18 inches of forest duf(overlyin� weathered hecoming unweathered horizons o(glaci.d �ill occaisionally o�'erlying a mixture ef oWwash sand and gr�vel with si:t depnsits. 'I'hc glacial till consists of sihy sand wilh gravcl, incrensing in den:ily with dcpth, and oflen cemenled. 'I'hc out�vash deposits rnnsist of densr to ��ery' dense sand wiih ��rying �moimts of silt. gravel, nnd cobbles. Fill soils �vere found in a shallow (Utree•foot deep) tcst pit excavated a� the edce of the water linc eusen:ent. Fill de,Ihs on thc order of G inchcs to I S inchcs are anticipnted on ci�her side of tlic trench :dong the len�hh of thc co�ridoc 'I'he fill soils, consisting of sihy snnd witli gravr,!, ovcrly Ihc original orcanic surf.icc soils. 'I'hc lill is most likely�he resull of grading out the Irerch spoils from Ihe excavation for inslallalian of thc utiliry. \1m•e dclailcd dcscriptions of �hc subsurface conditions �ec obscr�ed ave summarized nn tlic 'fest I'it Logs in Appendix A. The approximate localions of ihe Icsl pils are shown on Figure 2. Thc Uish•ibuiion «ud Deacripdmr o( Geningir Uuils !r� 1Ge iYhrkilleo Qunrh•n»gle, Il ii.chi»gtmi. by Jamcs P. Viioard (19g2), indicates the site is underlain by Vnshon Till (Q�'t). This published description is consistcnt with the deposits observcd in thc test pi�s c�caanled at the siie. [iased on our�est pits and the preseuce of sands and gravcls bdo�v 8 I8)'Cf O� �Ii1C18I UII silty sand w�ith gravcl, wC L7CIICVC lI7C µ'etilCRl CXICIII Ot �I1C SI�C Illily filOfC accur.dely be descri6ed as Advanced oul�vash(Q��i). 3.3 Groundwnter ��'c did no� observe ground��•ater secpage in any of �he te:;t pits ndvanced on-site. Reddish colored soils werc obscrvcd in the upper �veathercJ glacial lill �s well as c.�ilhin thc upper one �O �«'� CCCI Of�I1C llllWeathcred horizon. Oxidized or reddish snils are nn indication of the presence of ground��aler flow at some point in time. The dcvclopment of a perched ground��ater table is typical for sites underlaiu by glacial till, paniculady during the wct wintcr and sprin�, months. lu gcncral, surfacc ��ater ih:u inliltrates through�he upper wcathered soil zone becomes perched on ihe underlyint, dense,ccmented till. The cemented till has a relatively low peilneaUility tliet impedes the do�vmcnrd migration of tL•c in�ilu'a�ed suiiace «'ater. As a result, groundwater��ill accumulate, and whcn combincd tivith a posiiive gradient, aill tend to tlo�+' Ialerally along lhc �ill conlact. Locally, such secpage is r�lcrrcd to as interflo��. Ground��atcr secpa�c from lhc Jiscontintwus out�vash pockcts and iayers may be encountercd and tvill be �realest during mid-winter nnd carly spnng monlhs. If cncountered, it is likely thnt flow rates will Ue modertde ��hcn first cxposed �vith flows dimi�iishin�as storage is depleted. :1,11 GLOI.OGICALI.Y 31A7.ARDOUS AI2EAS The Ciiy ol' [acrett \lunicipal Code (GMC) descrihes geologically hazardouti areas ns erosion, landslide :^.r,d seismic or liqucl'action h;v;ird areas. 1�or detem�ination oi�these arcas, qie L•\4C refcrs to classilicaiions as stated in the "Dnmes and tv1oore Mclhodology for thc Invcn�ory, Classitication and Designation of Geologically I lazardous Arcas,City ol'Lvcrett, \V:ishington: July I, 1991". Pagc Ao. 3