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RECENLiles <br /> 0 �, 1 Z�}z • Q <br /> En-4o G. BAow-Jn. <br /> d i 1 ur,v ,,on <br /> W�0 <br /> "I' EN\ARONMENTALHFALTH s�w"�H poknalnuez <br /> Water Boards PERMITISERVICES ENYiliun,Af HI Rt I,oSCCI X,,, <br /> Central Valley Regional Water Quality Control Board <br /> 11 June 2012 <br /> Mr. Reyes Franco <br /> Pilkington North America, Inc. <br /> P.O. Box 128 <br /> Lathrop, CA 95330 <br /> SOIL INVESTIGATION REPORT COMMENTS, PILKINGTON NORTH <br /> AMERICA, LATHROP, SAN JOAQUIN COUNTY <br /> Staff of the Central Valley Regional Water Quality Control Board (Regional Water Board) <br /> have reviewed the 23 February 2012 Light Non-Aquesous Phase Liquid (LNAPL) <br /> Remedial Feasibility Study (FS) submitted on your behalf by Conestoga Rovers and <br /> Associates. Pilkington North America (PNA) discovered a release of diesel fuel (TPHd) <br /> in 1996, and initially recovered about 5,000 gallons of TPHd from the water table. Since <br /> 1996, an additional 225 gallons of TPHd has been skimmed from recovery wells. PNA <br /> submitted the FS in response to a 15 April 2011 Regional Water Board letter requesting <br /> assessment of further remedial options to enhance the rate of LNAPL recovery, thereby <br /> hastening the time,when closure can be considered. <br /> The FS evaluates the spatial distribution of TPHd and assesses its mobility, concluding <br /> that the plume is stable and diminishing, and the residual TPHd is largely immobile, <br /> weathered, not volatile, and has low potential to be recovered. The FS also concludes <br /> that there is low risk of exposure to sensitive receptors. <br /> The FS evaluated three remedial options, including <br /> 1. Monitored natural attenuation (MNA); <br /> 2. Enhanced biodegradation; <br /> 3. Active skimming with periodic high vacuum multi-phase extraction events. <br /> Evaluating remedial objectives relating to risk and mobility, the FS concludes that there <br /> is no feasible, economic option to enhance TPHd recovery; and recommends adopting <br /> MNA as the final remedial option. <br /> The State Water Resources Control Board Resolution 68-16, the anti-degradation policy, <br /> requires that existing water quality be maintained in all waters of the State. Therefore, <br /> any spills must be cleaned up to background water quality unless it is technically or <br /> economically unfeasible to do so, in which case cleanup must achieve at least water <br /> quality objectives. Groundwater at the site is classified as municipal, therefore the water <br /> quality objective for TPHd is 100 ug/l, the taste and odor threshold. The investigation <br /> must show that the Water Quality Objective has been attained or provide a trend of <br /> decreasing pollution that shows the Water Quality Objective will be obtained in a <br /> KARL E. LONGI-EV SCC, P.E., CHAIR ` PAMELA C. CREEOON P.E., BCEE, EXECUTIVE OFFICER <br /> 91020 Sun Ce Mer Drive 4200,Rancho Cordova.CA$5070 I www.wa[erboa rd s.ca.q.ov/contra Iva lley <br /> 1;p ne[:rer.en r`-1 <br />