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The:Customer CompanyY-'3 rl *January.30, 2012 . <br /> • In-Situ Soil Remediation: No soil remediation has been conducted X- <br /> V <br /> V-: ': `Groundwater Remediation: M groundwater°remediation has=been conductedwvw <br /> - <br /> General Site Conditions .. <br /> • -Geology and Hydrogeology:- The Site is underlain.by interbedded and intermixed sand, <br /> silt and clay. The depth to groundwater is approximately 8 feet bgs•and the groundwater <br /> gradient is southwest at approximately 0.0064 ft/ft G ; <br /> -'Groundwater Trends:^There a`re more than 23 years of g"roundwaterho'hitoring-data for` <br /> • this Site. MTBE trends are shown'below, source.area (MW-4) and down gradient F <br /> `(MW-1)_ .Y:--` .fq '';'Yx a�,��. "t a$"•�' a:."i[I. 1 }�' �:` .�,.f y r _: r Y i iter •lc:: x``..a .J <br /> METHYL-TERT-BUTYL'ETHER MTBE Results for MW-4 <br /> i9001i <br /> FAO <br /> 700 -_.. ..�-.. ..,--..;(.�. _ L •..�:.i ___ �.i '�: 16 .• Y L --A .F ... <br /> Boo i' -'-}- -s -" T",�j -_ _.. ._ i. ..� r �1;•�1sN re ' <br /> f w <br /> Ox <br /> cy.....•..n. ., - r - '- 500 <br /> - g3 400 <br /> yY Cr <br /> 9300 <br /> i. ., ..li }�,,�� <br /> 1i' G0 M.a, Y.-. Y,� L �'�+•.,• ?. '�._.. -. - -S S-7.1,ISiw!...AV <br /> 200 y �• 1. � I <br /> •":°.'-'. l• !-ya .lr.,i 100 <br /> . i. <br /> «r, II •.w.METHYL-TERT BUTYL ETHER(MTBE) Trend <br /> 17 <br /> ( e - <br /> METHYL-TERTBUTYL ETHER.(MT..BE) ,Results forMW-1 w i' <br /> :K r . <br /> (S .r <br /> 120 •- � ' 4a <br /> a.rs ••ii j r I �. .,i 1•, t <br /> 100 <br /> ' 60 <br /> 40 <br /> 60 <br /> v• 201.,o ;_ 't.+ya�+.,: y'+.• .' qpy , �` "^' .+-.y,..-l" - ' . <br /> v. '.!a6.1F:^1.�..'.ri' •)7 y„�,,N rvk.�,Ni: ,i.. __r <br /> '( �.e METHYL TERT BUTYL ETHER(MTBE) Trend <br /> Sensitive Receptor Survey <br /> A Sensitive Receptor Survey .(SRS) was conducted by ATC.&Associates. A records search at <br /> the Department of Water Resources and an on-the-ground survey in the area identified two �+ <br /> water supply wells within a 2,000 foot radius of the Site. Drinking water at and d near the Site is <br /> currently supplied by the City of Tracy Public Works. <br /> r <br /> Risk Evaluation <br /> A soil vapor survey and human health risk assessment was conducted in September 2010 by <br /> ATC &Associates. Four soil vapor samples were collected"and one or more samples exceeded <br /> ESLs thresholds. However, Tier 2 modeling determined that vapor migration risk did not exceed_ <br /> the cumulative hazard quotient or the incremental cancer risk for residential or commercial land <br /> use. <br />