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i <br /> (( <br /> 2000 Opportunity Dr, Suite 110, Roseville,California 95678 <br /> CONESTOGA-ROVERS Telephone: 916.677.3407,ext.100 Facsimile: '916.6773687 <br /> &ASSOCIATES vvww.CRAworld.com <br /> RFE C I �FL, <br /> � May 27; 2008 <br /> Ms. Victoria McCartney <br /> k'A" 2 3 2008 <br /> San Joaquin County ENV!R"1"4101EN T HEALTH, <br /> Environmental Health Division � Prpr,al�s'r'^FPVICES,zrl� , <br /> 600 East Main Street <br /> Stockton, CA 95202 <br /> Re: Well Destruction Workplan <br /> Chevron Service Station #9-1452 <br /> 334 East Main Street <br /> Ripon, CA <br /> Dear Ms. McCartney: <br /> On behalf of Chevron Environmental Management Products Company(Chevron), Conestoga-Rovers& Associates <br /> (CRA)is submitting this workplan to properly destroy ten groundwater monitoring wells(MW-1,MW-2,MW-3, MW- <br /> 4,MW-5S,MW-5D,MW-6S,MW-6D,MW-7D,and MW-8)at the site mentioned above. The wells will be destroyed <br /> in response to a site closure letter from Region Water Quality Control Board, Central Valley Region dated, May 16, <br /> 2008 (Attachment A). Presented below is the site background and CRA's detailed proposed scope of work. <br /> I <br /> SITE BACKGROUND <br /> Site Geology and Hydrogeology: The elevation of the site is.approximately 70 feet above mean sea level; the <br /> topography surrounding the site is relatively flat. Boring logs indicate soil beneath the site consists of silt with <br /> interbedded sand and silty sand lenses ranging in thickness from approximately I to 8 feet to approximately 40 feet <br /> below grade (fbg). A review of the boring log for CPT-1 indicates soil below 40 fbg consists of clay and stiff fine- <br /> grained sediments from 40 to approximately 70 fbg,a sand layer from 70 to 85 fbg,stiff fine-grained sediment from 85 <br /> to 105 fbg,and sand and sand mixtures with silt from 105 fbg to the total depth explored of 120 fbg. Review of CPT-2 <br /> indicates silt and clay mixtures with alternating stiff fine-grained sediments from surface grade to an approximate depth <br /> of 64 fbg, a sand layer between 64 and.-92 fbg, stiff fine-grained sediment from 92 to 1 l 5 fbg, and a sand layer from <br /> 115 fbg to the total depth explored of 120 fbg. <br /> Groundwater beneath the site historically ranges from approximately 28 to 35 fbg. Historical groundwater elevation <br /> data infers a consistent flow direction toward the southwest at an approximate gradient of 0.001 feet per foot(ft/ft). <br /> The southwest flow direction is consistent with other sites in.the vicinity. <br /> Equal <br /> Employment <br /> Opportunity Employer <br /> Worldwide Engineering,Environmental,Construction,and IT Services <br />