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4 ,,h'I {I I�^E;D EONYNo G Be...Je. <br /> -sir W f S� ----Ron <br /> a.cr.eear. MAR 2 2 20131 Mnvwew RODRIGUEZ <br /> FOR <br /> Water Boards `/ e.VRONMnEN PROTECTION <br /> Central Valley Regional Water Quality Control Board <br /> 19 March 2013 <br /> Mr. Benson Cuthbertson <br /> Pilkington North America, Inc. <br /> 500 E. Louise Avenue <br /> Lathrop, CA 95330 <br /> RESPONSE TO CLOSURE REQUEST , PILKINGTON NORTH AMERICA, 500 <br /> E. LOUISE AVENUE, LATHROP, SAN JOAQUIN COUNTY <br /> Staff of the Central Valley Regional Water Quality Control Board (Regional Water Board) <br /> have reviewed the 7 February 2013 Case Closure Request(Closure Report) submitted <br /> on your behalf by Antea Group for a diesel fuel spill at 500 E. Louise Avenue in Lathrop <br /> (Site). Pilkington North America (PNA) has been remediating the diesel spill since 1996 <br /> by periodically skimming diesel from recovery wells. The Closure Report requests <br /> closure of this site as a low-risk closure. <br /> As explained below, based on our review of the facts of the case, the Central Valley <br /> Water Board denies PNA's request to grant site closure or a no further action <br /> determination at the site. This decision is based upon our determination that there has <br /> been insufficient characterization of the extent of the groundwater pollution, there may <br /> be additional sources of pollution, and that the site conditions may affect cleanup actions <br /> at adjacent properties. <br /> Background <br /> Pilkington North America (PNA) discovered a release of diesel fuel (TPHd) in 1996 from <br /> subsurface piping associated with a 10,000 gallon Above Ground Storage Tank. PNA <br /> identified the origin of the leak to be from an underground elbow in a supply line to a <br /> generator. PNA excavated the TPH-contaminated soil below the release to a depth of <br /> 13 feet. No groundwater-diesel interface was noted and the diesel surface stabilized at <br /> about 9 feet below ground surface (bgs). PNA recovered about 3,000 gallons of diesel <br /> fuel and another 2,000 gallons of a diesel/groundwater mixture by pumping from the <br /> excavation. In December 1999 PNA installed eleven Geoprobe borings to approximately <br /> four feet below the water table, or about 15 feet bgs. <br /> In June 1999, PNA installed six diesel recovery wells and three groundwater monitoring <br /> wells to a maximum depth of about 17 feet bgs. Since 1999, PNA recovered about 234 <br /> additional gallons of TPHd by.periodic skimming from recovery wells. <br /> Regional Water Board staff, in a 7 September 2010 letter, requested PNA investigate <br /> whether residual LNAPL on the water table could be the result of an undetected leak. <br /> KARL E. LONOLEV SCD, P.E., CHAIR I PAMELA C. CREEOON P.E., BCEE, EXECUTIVE OFFICER <br /> 11020 Sun Center Drive 4200,Rancho Cordova,CA 95670 1 www.waterboards.ca.9ov/centralvall.y <br /> 0 nEermeo Paree <br />