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03/01/00 WED 18:02 FAX 510 893 8205 CH2N HILL Q002 <br /> CH2M HILL <br /> 1111 Broady <br /> P.O.Box 12661 <br /> Mvd.CA <br /> CH2MHILL 94 -Ml <br /> 'Cel 510.291.2420 <br /> Fax 510.M.0Y05 <br /> March 1,2000 <br /> 13142-O.A1.08 <br /> Ronald Rowe <br /> San Joaquin County Public Health Services <br /> LOP/Site Mitigation Unit <br /> Environmental Health Division <br /> 304 E.Weber Ave.,Third Floor <br /> Stockton,CA 95202 <br /> Subject: Disco Site-Additional Investigation <br /> 110 Filbert Street,Stockton California <br /> Dear Mr.Rowe; <br /> As per your phone message of March 1,2000,this letter serves as a final proposal for <br /> borehole locations for the additional CPT investigation at the Disco site,located at 110 <br /> t. Filbert Street,Stockton,California, <br /> In concurrence with your reconunendation,we are proposing to install 6 additional CPI' <br /> borings at locations shown on the attached figure.The purpose of the borings is to assess the <br /> extent of petroleum hydrocarbons downgradient,and cross-gradient from the site.Four <br /> borings shall be installed on the shoulder of the south side of Highway 4,downgradient and <br /> across the freeway from previous borings CPT-6,-7,and-8.One additional boring shall be <br /> :installed east of CPT-8,on the north shoulder of Highway 4.Each of these borings will be a <br /> maximtun of 130 feet deep,and two groundwater samples will be collected from each <br /> boring.One groundwater sample will be collected from the zone around 75 ft bgs and one <br /> sample will be collected from a deeper zone(exact depth will depend upon the lithologic <br /> logs).One additional boring shall be installed onsite,between boring CPT-5 and monitoring <br /> well MW-DIS-9.Groundwater samples will be collected from the zone around 100 ft bgs <br /> and one sample will be collected from a deeper zone(exact depth will depend upon the <br /> lithologic logs).We will follow the same sampling methodology outlined in the October 8, <br /> 1999 "Work Plan far Additional Investigation at the Disco Property (CH2M HILL,October <br /> 1999)_ <br /> All groundwater samples will be analyzed for the following: <br /> • TPH-gas/STEX,by EPA Method 8015M <br /> • Oxygenates,1,2-DCA,and£DB by EPA Method 8260 <br />