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; <br /> tu the access road embankmcnt. �Vu underst:�nd tnat an old barn exis[ed on thc northem portion of the site <br /> and was rcccndy dcmolishcd. Concrcte slobs �nd associatcd filUgra��cl arc prescnt �vhzrc thc U�m n�s <br /> situa[ed. <br /> � REGIONAL GEOLOGY <br /> Geologic information for the project �'iciniry �vas obtained t?om die map prepared b}� tilinard (1985). All <br /> of Smrth Island is mappe� as being composed of younger al?uvial and estuarine deposits. These deposits <br /> consist of stratified sediments laid down Uy the strcams and rivers in the area. The sediment deposits <br /> consist of silt, sand and clay with organic matter. Pcat �eposits ha��c also been mapped in the Smith <br /> Island arca. <br /> SUBSURFACE CONDITIONS <br /> Gerterel <br /> The native subsurface conditions cncountcicd in the csplorations compictcd for Ihis study and for <br /> previous nearby projects are relativcly consistent. In general, iopscil and/or 61l in isolated loc:itions <br /> overlie recent alluvial and estuarine deposits cansisting of compressible fine-graincd soils composed of <br /> , organic silt, and silt widi interbedded sands. 'Che compressible fine-grained alluvial soils are generally <br /> underlain at depth by coarser-grained alluvial deposits consisting of sand with variable silt content and <br /> occasional silt layers. �Vhere thc cxplora[iuns wem extendcd to sufficicnt depth, a deeper compressible <br /> silt laycr ��';is cncounlcred bclo�� Ihc cuarscr-graincd alluvial dcposits. Thcsc imits arc discusscd in morc <br /> detail bclow. <br /> Topsoil <br /> "I'opsoil consisting of gray-brown to urungc-bro�cn, organic rich silt/silt}� sand �cith raou from surfaer <br /> vegetation was generally obscrved in the upper hvo to three feet of the soil profile in cach of thc <br /> explorations. Topsoil at the site incfudes soil disturUed and modified by historic farming activities. <br /> Fill Soils <br /> I [mported fill soils and/or reworked native soils ���ere directly observed in the northem portion o�the sitc <br /> in boring B-I and test pit TP-2 �vhcre the old bam and associated improvements existed. In general, thc <br /> fill consisted of brown silty sand. In test pit TP-2, thc fill included concrete rubble mised into tne <br /> underlying tine-gra�ned soils. The fill at TP-1 appeared to be associated with site drivcway constructiun. <br /> Although not dircctly obsen�ed, fill also exists in die northcasVsouthw�st trcnding access road <br /> cmUankment that traverses across thc wesrem portion of the site. <br /> Fine-Grained Alluvial Deposits <br /> The site is gcnerally underlain by compressible native tinc-grained deposits consisting of recent alluvial I <br /> and esmarine deposits. These deposits are composcd of organic silt, silt, and interbedded silts and sands. <br /> The organic silt and silt deposits �� �e obsen�ed in all the test pits and they generally ranged from 12 to <br /> over 20 feet thick. The es[imated thickness of the compressible layers at the site is shown on Figure Z. <br /> The organic silt deposits were commonly observed overlying silt having little oreanic matter. The <br /> orbanic silt generally ranged �iom 3 to I 1 feet thick, whife the underlying silt deposits ranged from 2 to <br /> ]0 feet thick. Thc organic silt and silt layers contain eariable amounts of fibrous organic material and <br /> accasional logs, up to about 12 inches in diameter, have becn obsen�ed in the same unit at nearby sites. <br /> Filt,Yo.d'937-OOJ-00 Pn4l'j GEOENGI4EEN� <br /> OtmLcr l!,?006 <br />