ARCHIVED REPORTS_XR0002117 - Laserfiche WebLink

Home Browse Search

• In July 1989, EA drilled three soil borings on site {SB-5 through SB-7) In August 1990, EA also drilled and installed wells MW-6, MW-7, and MW-8 in the vicinities of wells MW-3, MW-4, and MW-5, respectively, because the latter went dry (Figure 2) Soil sampling analytical results are summarized in Table 5 ' In 1990 EVAX Technologies{EVAX} of Sacramento, California, conducted another ' soil vapor survey The results of the survey indicated up to 19,000 ppm of volatile hydrocarbons beneath the former UST basin • EVAX operated a soil vapor extraction system on the site from March through ' December 1991 An estimated 1439 pounds of petroleum hydrocarbons including 60 pounds of benzene were removed from the subsurface ' The depth to groundwater beneath the site has increased from a depth of approximately 47 feet in 1987 to 60 feet in September 1992 The wells have been ' sampled periodically since 1986 Analytical results of groundwater samples from the wells have not indicated the presence of petroleum hydrocarbons since June 1991 4 0 REMEDIATION CONFIRMATION SOIL BORINGS In November 1992, EA submitted a workplan, Work Plan For Soil Sampling, Former Exxon Retail Site 7-1050, 909 West Hammer Lane, Stockton, California, to the San Joaquin County Environmental Health Department to drill and sample three soil borings to assess the effectiveness of the vapor extraction system The workplan was approved and Aegis was contracted by Exxon to install the borings On June 3, 1993, Aegis drilled three soil borings, SB-8, SB-9, and SB-10 (Figure 2) to ' confirm soil remediation The locations of the soil borings were based on a) previous soil sampling locations, b) EA's workplan, and c) input by the San Joaquin County Environmental Health Department (SJCEHD) These locations represent what was Iconsidered by the SJCEHD as the area most impacted by the leaking UST system I4.1 Sod Borings The three soil borings were drilled using 8-inch diameter, hollow-stem augers following Aegis' Standard Operating Procedures (SOP) included as Appendix A The borings were drilled to the first occurrence of groundwater, typically 58 feet Soil samples were collected at 5-foot intervals in each boring To fully characterize the soil, all samples (36) collected were submitted for laboratory analysis Boring logs are included in Appendix B 93 0056 QMR 2