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December 19, 1986 Harding Lawson Associates <br /> 4167,154.02 <br /> Exxon CmTpa7y, U.S.A. <br /> Mr. Kent Sanderson <br /> Page 2 <br /> volatile organics (by EPA Methods 8010, 8015, and 8020) and for total <br /> lead (by EPA Method 6010) in accordance with the request of the sJcHD. <br /> Detectable hydrocarbons were found in two soil samples collected from <br /> beneath the fuel storage tanks a depth of approximately 12 feet below <br /> ground surface. Soils from the waste oil tank excavation had nondetect- <br /> able hydrocarcbn concentrations. Some 300 cubic yards of fill material <br /> excavated during tank removal was stockpiled on site adjacent to the <br /> excavation. <br /> On September 4, 1986, HLA received verbal authorization from Mr. Kent <br /> Sandexson of Exxon to perform follow-up work at the site, to consist of <br /> additional soil sampling and treatment of the soil by aeration. <br /> The service station at the site is closed and pending a transfer of <br /> ownership- It is our understanding that station demolition and subse- <br /> quent commercial construction is planned for the site. <br /> INVESTIGATION <br /> Field work was conducted at the site between September 9 and November 21, <br /> 1986 and included six site visits by our geologist. The services pro- <br /> vided by HLA are summarized below: <br /> 1. Vapor-surveyed and collected soil and ground-water samples during <br /> remedial excavation of native soil from below the former fuel tank <br /> locations. The purpose of additional excavation and sampling was to <br /> evaluate the vertical and lateral extent of hydrocarbon contamination <br /> in accordance with the requirements of the S7CLHD. <br /> 2. Vapor surveyed and collected soil samples from stockpiled soils <br /> before aeration to document initial hydrocarbon concentrations. This <br /> data was required by the SS7CAPD for aeration <br /> pe=t application. <br /> 3. Vapor-surveyed and collected soil samples of areated soils to docu- <br /> ment final hydrocarbon concentrations. 'Iris data was required by the <br /> SJCIHD prior to its authorization of the on-site use of aerated soils <br /> as backfill material. <br /> A log of site visits and work accomplished is attached. <br /> Remedial Excavation and Samolircr Prccedurs <br /> On September 23, 1986, the fuel tank excavation was deeoered from 10 feet <br /> to a depth of 21 feet 1�elcw grade. Using an organic vapor analyzer <br /> (OVA) , we surveyed the soils for hydrocarbon vapors during excavation and <br />