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..�.� <br /> w�-a��ao n� <br /> Attn: Mr.Tunv Vi�olo, N.E. <br /> � w )une 16, 1988 <br /> p �° � Page 2 <br /> Y � N <br /> H � <br /> � r <br /> o � o <br /> � N M <br /> � � � All sarnp�cs w'erP �2�'.cn to our iat��rarory in Seatdc, w hcrc each vras visually classificd and its <br /> .. K watcr conccnt detennined. Four samplcs w�ere testcd :or grain-size distribution. A Dtodified <br /> Hz ' Proctor compacti�n�^.; •�'.:;�erformed on a rcpresentauve sample of the native near-surface <br /> y H � 501�5. I ' <br /> t� M I <br /> � �' .. Water contcnts are presented on thc test pit logs.Graimsize disvibu''ans are presen�ed on <br /> � r Figures 7 and 8. The results of the compaction tcs: are presented on Figure 9. li <br /> � � � t;eoloeic ('onditions I <br /> The soils encountered in thc test pits at the proposed reservou site are the products of the last �I � <br /> glaciation in this portion o(the Puget Sound Lowland. IIasa!lodgement till, locally called <br /> "hardpan", w�as found in the bottoms of all of the test pits at the sice. This matenal is dense ro <br /> very dense, gray, silq�, gra�'elly sand with scattcred iror �xide stains. Overlying the rrl�tiveh <br /> unweathcred �ill is a zone of weathered till which gener�lly varies(rom medium d�nse to dense <br /> and com�ins iron o�ide stains and scatcered roc�:s. The rnntact beiu'een the weathered till and <br /> underlping unN eathercd till ranged from 2.5 to 3 feet decp in the explorauons. The su�cial <br /> soil laycr diroughout t:ie resen�oir site is an organic-rich topsoil,comprised of very loose to <br /> loose,orange-bro��n, tinc gra��elly, silty sand to sandy silt,w'ith numerous roots. The <br /> thickness of this zone varied (rom 6 io 12 inches in the test pits. <br /> � <br /> i�� The ground-u�ater table is perennially high in this area,as e��denced by the presence o(large <br /> � encounte ed n i eeNea he cdti Il�sv n on�op���ha u�l i all ofethe�explorauonse was <br /> ' C'nnclutinns�nd Recommcnd�tiona I <br /> �"'� n nl <br /> Dense to ven•dense, siliy, @ravelly sand (gl�cial till i �'as er.countercd at shalloµ•dep�hs at the <br /> lanned reservoir location. "Ihis glacial till is capable o(swpport�ng the anticipated loads H�Ith <br /> � t~'�� minim�I senlements,in our opinion The soilc o��erlying the glacial tili contam varying <br /> amounts of roots and organics and are less dense,and we recommend they not tx used to <br /> suppun the proposed tank. Exca�ations could gener:�ly be accompli. .cd with com�entionai <br /> eqwpment, although a bulldbzer with a ripping tc�l may exp� iite site excavatio�is in ihe glaci�l <br /> �•� till. 71�c tesi pits excav�ted (or this prujeci extended app���.�mately 6 io 7 feet inw the verp <br /> Jcnsc glacial till and were duc µith a rubbct-tired, vactor-mountcd backhoc. <br /> �. The following scctions contain additional rcconvnendations(or si�e preparation and eanhHork, <br /> ��� found�tion design,and drainagc. <br /> Cur t�rcn�r;iti�m <br /> 'I .�.,.� N'e recommend diat the elevauon of the bonom of th^rcscrvoir he ulected so that the bottom <br /> \� plete(or the mai of oil-treated sand)w�ill be placed directly ntop a leveled surface in the very <br /> dence @lacial till. V�'here backfill beneath the tank is nzcessary, such as along the ringwall, it <br /> shoul� be compacted structursl fill. <br /> SHANKON d �ti'�LSON INC <br /> l <br />