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1 LV GJ JJ J. 1 . •��♦ •.�. . ...i.. �...• . �L <br /> � . �. �. ����� •�.i� �_�� � � . �• <br /> Glcmvood Terrncc <br /> Filc Numbcr 12699? <br /> May l2, 1994 <br /> Page 5 <br /> sccn today arc a result of scouring and ovemding by glacial ice. During thc Vashon Stade, thc Puget <br /> Sound r�gion tvas ovemddcn by over 3,000 fcet of ica Soil layers overridden by tl�e icc sheet were <br /> compactcJ to a much g�wter extent than those that ware not. All three of Ihe abovc described geologic <br /> units werc ovemdden by the glacial ice. <br /> Soils <br /> Ceneral: We prcviously explored subsurface conditions at qie site by cxcavating 34 test pits in 1987 using <br /> a rubbcrvtired tractor-t}ye back}ioo. 7Tic results of our investigation are presented in our feasibility study <br /> Iettcr, We have includcd thc exploration infortnation from thc previous study in this rcport, rcfer io <br /> Appendir A. Subsudacc conditions were furlher explortri at d�e site in April 1994 by excav�ting 8 test <br /> pits, using a rubber-tircd tractor-typc backhce widi an extend•a-lice attachnient. M extend-a-hoe type <br /> back hoc was used in order to excavate to depths greater than diose previously actiieved in 1987. The test <br /> pits �eere locatixi in U�c ficld by a Qeologist, representing ihis firtn, �t�ho maintaincd logs of die conditions <br /> cncountcred. 'R�c location of thc tcst pits excnvatrd in 1987 and 1994 are sho�m on Ihe 5ite Plan in Figure <br /> 2. Cross-scclions oi specific areas showing surface and subsurfacc conditions are prescntcd in Figures 3 <br /> through B. Tlic soils�vcre classified in general accordance to the Unificd 5oil Classification system, a copy <br /> of which is presentcJ in �iguro 9. Tlie test pit logs�re prcsenled in Figures 10 U�rough 1 t, <br /> 7'he site is undcrlain at dcpth by transitional beds(Qtb). 'Ihese soils consist of light bro�m, medium dense <br /> to dcnsc, fine to mcdium sand with occasional coarsc sand and gravcl,cappcd witli an intcrbcdded scqucnce <br /> of dense, silh� fine to medium sand. 71�is unit was encountered in the test pits in the area of the detention <br /> pond. O�•erlying die Qtb, we encountered advancc ouhvash. 'Il�e outwash cousists of light gray, light L1n <br /> and bluish-gray, dcnsc, finc to medium sand with tnce :unounts of silt. 'Ihe outwosh is Uie matcrial that <br /> was previously quamul. Overlying Oic ouhvash,«c cncountered fill. Tl�e fill consists of inedium gray and <br /> bro��ro, loose to medium dense, silty fine ro mcdium sand with varying runounls of coarse sand, gravel and <br /> org:u�ics. The fill ranges over l8 feet in dep(h in U�e middle of the site and near the northcrn slopc. We <br /> cncountcrcd glacial till (Qvt) on top of ll�c ouAvasl� in ttie higticr portions of the site. The till consists of <br /> gray,densc to vcry dcnsc,silty fine to mcdium svid���itli varying amounts of gravel:u�d cabblcs. <br /> Fill Slope Aren: 71ie north cenlral portion oP the site is widerlsin at dcpth by advance outwash (Qva). <br /> 71ie top portion of dic ouhvash ranges Gom 7A to o��er 18.0 feet in JepO�. Thc fiU (dcscribed in the � <br /> Generel subsection) estends Gom tlre ground surface to die top of the ouhvash, '['he backhce could not ¢ _ 7 <br /> extend U�rough Uie fill in tcst pit 2 or 4 �rhich are locatecl approximately in the center of the planned <br /> improvements and at Uia break in slopc near die north property line, respectfully. 'I7ie fill in the arca of We <br /> NELSON-COUVRETTE 8 ASSOC/ATES, INC. <br /> r-�e-zs-i4a� i?:ns 206 �ei zsie 96: P.07 <br />