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.wv4.r EDMUND G. BROWN JR. <br /> GOVERNOR <br /> C L I!O A M I• MCTET�Ew RODRIOUEZ <br /> RR <br /> WaterBoards ENVIRONMENTAL PROTECTION <br /> Central Valley Regional Water Quality Control Board RECEIV <br /> MAY 19 2014 <br /> 16 May 2014 <br /> ENVIRONMENTAL.HEALTH <br /> PERMITISER=ES <br /> Mr. James E. Diel <br /> Manager of Environmental Site Remediation <br /> Union Pacific Railroad Company <br /> 9451 Atkinson Street, Suite 100 <br /> Roseville, CA 95747-9711 <br /> NATURAL SOURCE ZONE DEPLETION EVALUATION, UPRR FORMER TRACY <br /> MAINTENANCE YARD, 720 EAST 6r"STREET, TRACY, SAN JOAQUIN COUNTY <br /> Staff of the California Regional Water Quality Control Board, Central Valley Region (Central <br /> Valley Water Board) reviewed the 29 January 2014 Natural Source Zone Depletion Evaluation <br /> Summary Report(Depletion Report), prepared by Arcadis on behalf of Union Pacific Railroad <br /> (UPRR) for the former Tracy Maintenance Yard. At the Tracy facility, a source area of diesel <br /> fuel covers about 3/ of an acre as a Light Non-Aqueous Phase Liquid (LNAPL). UPRR is <br /> comparing the rate of LNAPL removal through intrinsic biodegradation to the rate of removal <br /> through physical removal by bailing from 6 monitoring wells quarterly. <br /> Physical Removal <br /> The amount of LNAPL removed by bailing varied substantially between wells and between <br /> quarters. Monitoring well MW-08A produced the lowest amount, from 0.04 to 0.18 gallons per <br /> quarterly event for a total of 0.43 gallons in 2013, whereas monitoring wells TW-01 and <br /> MW-06A produced between 0.7 and 2.25 gallons per event for more than 5 gallons each for the <br /> year. Overall, 18.7 gallons were recovered from all 6 wells over the four quarters. <br /> Carbon Dioxide Flux <br /> During biological degradation of organic material, carbon dioxide is produced, whch can be <br /> captured in a flux chamber. Two flux chambers were placed over the LNAPL area and two flux <br /> chambers were placed outside of the LNAPL area to measure carbon dioxide production over a <br /> 14-day period. Flux measurements were made in February and in November 2013. in order to <br /> separate degradation of fossil fuels from degradation of fresh organic material, the flux chamber <br /> contents were also analyzed for carbon 14 isotopes (14C). Any 14C detections are assumed to <br /> be from degradation of carbon compounds of recent origin, not from fossil fuels, and were <br /> subtracted from the total measured carbon dioxide in order to produce an estimate of <br /> degradation of fossil fuels. <br /> The carbon dioxide production attributed to fossil fuel degradation measured over the LNAPL <br /> was about an order of magnitude greater than that measured from the background flux <br /> chambers, demonstrating that biodegradation is occurring. However, Central Valley Water <br /> Board staff do not have confidence in the proposed rate at which the LNAPL is degrading. <br /> KARL E. LONGLEV SCD, P.E., CHAIR I PAMELA C. CREEDON P.E., BCEE, EXECUTIVE OFFICER <br /> 11020 Sun Center Drive$1200,Rancho Cordova,CA 95670 1 www.waterboards.ca.gov/centralvalley <br /> 45 RECTCLEU—1— <br />