3003 W CASINO RD 1992 SITE DEV 2018-01-01 MF Import

Rcid Middlc�im & Auii�iales Septemncr 2, 1992 Pagc 3 ahove the downsVcam (north) tuc. An unimpruveJ scrvice road eztends eastward from the dam crest approximately 250 feet to the paved Pluke West Entry Road. The dam is vegetatal with grasx, alder saplings and scotch hroom, and thc. crest is covered with a thin layer of grave;. We ohserved no evidence of seepage on the dam face or in the ahutment areas. Minor surface erosion has ocwrral on the lower portions of the abutmenGt on the downstream side, as indicateci hy shallow gullies generally less than 12 inches deep. It appears this is the result of surface water runoff from the dam face. A small permanent pond occupies the hottom o( the detention pond area immaliately upstream of the dam. Thc watcr surface is at an elevation o(approzimately 452 feet. The pond, which measures approximately 50 fect by 25 fect anJ is abuut 3 feet deep, is vegetat�i with various ayualic species. An impervious liner covers the bottom of the permanent pond. Dased on our review of the design and cunstruction Jucumems, we unJerstand this liner consisls of:� compactul thickness of 2 feet uf silly sand anJ gravcl (glacial till) plac�l Juring the pond constniction. f3aseci on our review of records penaining w cun�tructiun of the earth dam, the bottom of the ravine sou;h of the dam was usul es a haul road fi�r trancportation of dam emhankment fill. 7his road is prcsendy uvcrgrown with grAss and Aldcr Irees. It appcars that the honnm of Ihc ravine north of the dam may alsu h�rve heen used :is ;i tempurary haul rn;id during constructiun. SUBSURFACE CONDITIONS General Subsurface cunditiuns at the site �ecre cxpinrrd hy drilling thrce hurings thruugh �he earth dam emhankmenl and imu the na�ivu underlying soils and hy excnv.�ting tive test pits in the vicinity of the detemian ponJ expansion. The horings, dexign.ucJ I3-I tu 13-3, were drillecl tu Jepths ranging from I S to 31.5 feM un August 24, I99?. "lhe test pi�s, designat�xl TP-I to 9'P-S. were excavalul to depths ranging frum 10 to 14 feet on August 25, 1992. Approximale lucatiunt of�he expluratiuns are shou�n in Pigure 2. Descripliuns uf Ihe tield exploration enJ lahoretor� I�.cling procedures are presentul in the att�chment. Lugs o( the explurations are includul :is Pigures A-3 lhrough A-8. In aJdilion to the explorations descrihul nhuve, we h.�ve recently completul test pits to thc , wes� and suwh of the detentiun pund as pan o( uur suhsurf�ce explor,�tion program for thc pruposal North Parking I:q. These tesl pits, designaleJ TP-7 and TP-S, were excavalal to a depth of 17 and 15 feet, respectively, un June 4, 1992. Logs i�f these explora�ionx are includ�J � in our drnfl report Jatecl June 22. 1992. Also, we completeJ fnur Iest pits at the present location uf Ihe earth dnm and detention poncl prior tu construction of these features. 7'hese text pits, designat�l TP-22 tu TP-25, wcre excavalul to depths ranging I}om 7.5 fcet to 10.5 feet on Septemher IS. 19R3. Logs u(these explura�iunx �ire included in our repurt d.ucJ lanuar� IG, 1984. Ap�iniximaie luc:ili��n� of tlicc� tir prcviuu� rzpinr�liu�is arr sh�n�n in I i�ure 2. r, , „ r n �� i n , , i . �,i. N.� n�znisnu�u