Laserfiche WebLink
9110 Thornton Road Chronology <br /> Page 4 <br /> Confirmation Sampling <br /> Groundwater monitoring wells were sampled periodically since the initiation of the <br /> investigation. <br /> A series of soil borings were drilled and sampled to evaluate the extent of residual <br /> soil contamination. <br /> A soil vapor extraction test was conducted on January 13, 1994 to evaluate <br /> concentrations of residual contamination. Also, the effective radius and the <br /> potential rate of extraction of the residual contamination was estimated. The test <br /> results continued to evidence the presence of hydrocarbon contamination and <br /> indicated that the effective radius was 100 feet with a potential extraction rate of <br /> 0.29 pounds of TPH-gasoline per day. <br /> Residual Contamination <br /> Due to limitations of remediation technology, residual soil and groundwater <br /> contamination continue to be evidenced at the site. Based on the number of <br /> groundwater wells and soil borings which do not detect contamination, the extent <br /> of residual contamination is limited. The volume of contaminated groundwater was- <br /> estimated to be 1512 cubic yards at 25 ppb total petroleum hydrocarbon as <br /> gasoline constituting approximately 0.003 gallons of gasoline. The volume of <br /> contaminated soil was estimated to be 450 cubic yards at from 2600 ppm to 1 .0 <br /> ppm total petroleum hydrocarbon as gasoline constituting approximately 10 gallons <br /> of gasoline. Based on the evaluation of Ed K. Simonis, Registered Geologist <br /> #4422, the potential impact that this residual contamination may have on <br /> groundwater quality was determined not to be significant. <br /> Site Closure <br /> Once the closure material has been reviewed by the Central Valley Regional Water <br /> Quality Control Board, and one additional monitoring and sampling event of the <br /> groundwater monitoring wells has been completed, San Joaquin County <br /> Environmental Health Division will direct Southland to submit a work plan to <br /> destroy all of the wells which were installed as part of their investigation and <br /> remediation effort. After the wells have been properly destroyed, San Joaquin <br /> County Environmental Health Division will issue a closure/site certification letter to <br /> Southland indicating that based on current land use and available information, no <br /> further action will be required. <br /> MMICLOSUREICHR91 10.SUM <br />