Laserfiche WebLink
California Regional Water Quality Con rol Board ,, ;::: <br /> Central Valley Region °0. <br /> Katherine Hart,Chair E " v1 <br /> 11020 Sun Center Drive,4200,Rancho Cordova,California 95670-611 <br /> Matthew Rodriquez (916)464-3291 •FAX(916)464-4645 Edmund G.Brown Jr. <br /> Secretaryfor http://www.waterbouds.m.gov/centralvalleyr' (� p Governor <br /> AEnvironmental Protection V 5 201<qq <br /> ENVIRONMENTAL HEALTH <br /> 30 December 2011 PERMlT/SERVICES <br /> DESJC, M.BENSON <br /> Defense Distribution Depot San Joaquin <br /> P.O. Box 960,001 <br /> Stockton, CA 95296 <br /> REVIEW OF DRAFT/FINAL RESULTS OF VAPOR INTRUSION MODELING AND DRAFT <br /> CORRECTIVE ACTION PLAN FOR BUILDING 255/UST 25, DEFENSE LOGISTICS <br /> AGENCY, DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN, TRACY SITE <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley Water <br /> Board) staff has reviewed the Draft/Final Results of Vapor Intrusion Modeling Building 255/ <br /> UST 25 (Modeling Report) dated 4 June and received 6 June 2011, and the Draft Corrective <br /> Action Plan — UST Site 25 (CAP), dated and received 19 September 2011. The CAP and <br /> Modeling Report were prepared by HDR Environmental, Operations and Construction, Inc. on <br /> behalf of the Defense Logistics Agency (DLA) for the Defense Distribution Depot San Joaquin <br /> Tracy supply depot. <br /> The Modeling Report summarizes the methods and results of vapor intrusion modeling <br /> performed to evaluate the risk to Building 255 indoor air from diesel-range total petroleum <br /> hydrocarbons (TPH)-contaminated soil and groundwater. The CAP presents evaluations and <br /> recommendations of remedial action alternatives to address soil and groundwater impacted by <br /> TPH beneath the surface near and under Building 255. Based on the report results, DLA <br /> concluded that there was no significant risk to indoor air and that semi-annual groundwater <br /> sampling of wells be continued to verify decreasing TPH concentrations. <br /> Background <br /> DLA installed Underground Storage Tank ( 1ST) 25 sometime before 4982 irr the south <br /> courtyard of Building 255 at the Tracy site. The 500-gallon UST was used to store diesel <br /> number 2 fuel oil for heating the building. In 1988, DLA removed the UST and excavated and <br /> disposed of an unknown volume of contaminated soil. At the time UST 25 was removed, only <br /> one soil sample was collected at an unspecified depth from beneath the tank location. <br /> Laboratory chemical analysis on the sample detected TPH at a concentration of 26,000 <br /> milligrams per kilogram (mg/kg). <br /> In 1993, DLA collected soil and groundwater samples from soil borings within and near the <br /> former UST excavation and performed laboratory chemical analyses. The maximum <br /> concentration of TPH was 18,200 milligrams per kilogram (mg/kg) in soil and 478,000 <br /> micrograms per liter (pg/L) in groundwater. In 1998, DLA collected soil and groundwater <br /> California Environmental Protection Agency <br /> pia Recycled Paper <br />