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--ol Board <br /> California "egional Water Quality Con* <br /> Central Valley Region <br /> Karl E. Longley, Sc D, P.E., Chair <br /> Linda S. Adams Arnold <br /> Secretary/or Sacramento Main Office <br /> I I tt2n tion Cemct Drnc n200.Rancho Cordova.Cahthnua y h70-61 13 SchwarzeneRger <br /> IJII.ironmemal (;orroior <br /> Protection Phone(U 16)-161-3291 •FAX(916)4644645, <br /> hnpJ.,xNvv r%%aterhoards ca eocrcentrahallec <br /> E C, E V E��D <br /> 26 March 2008 MAR 2 8 2008 <br /> ENVIRCN,%IENT HEALTH <br /> PERMIT/SERVICES <br /> Mr. Joe Aldridge, Remediation Manager <br /> NuStar Energy L.P <br /> 2330 North Loop 1604 West <br /> San Antonio, TX 78278 <br /> MONITORED NATURAL ATTENUATION EVALUATION REPORT, 2941 NAVY DRIVE, <br /> STOCKTON, SAN JOAQUIN COUNTY <br /> Regional Water Quality Control Board - Central Valley Region (Regional Water Board) staff <br /> reviewed the 29 February 2008 Monitored Natural Attenuation Evaluation Report (Report). <br /> Ash Creek Associates, Inc. (Ash Creek) prepared the document on behalf of ST Services, <br /> L.L.C. (a subsidiary of NuStar Energy L.P. [NuStar]) for the ST Services Stockton Terminal <br /> located at 2941 Navy Drive in Stockton (Site). Nustar recommends selecting monitored <br /> natural attenuation (MNA) for groundwater cleanup at the Site. <br /> Nustar submitted the Report in response to the Regional Water Board's 13 August 2007 letter, <br /> which requested additional evaluation in support of this remedial option, while explicitly <br /> disagreeing with the rationale for selecting MNA. We also discussed submission of the Report <br /> in a 9 July 2007 meeting attended by Mr. Joe Aldridge of Nustar, environmental consultants <br /> Ms. Amanda Spencer and Mr. Andrew Schmidt of Ash Creek and Ms. Wendy Cohen and me <br /> from the Regional Water Board. <br /> Based on four quarters of MNA assessment monitoring, NuStar concluded that MNA is <br /> occurring at the Site anaerobically by methanogenisis using sulfate as an electron acceptor. <br /> NuStar based this conclusion on observations that included the lack of separate phase <br /> hydrocarbons (SPH) in source area wells (ST/MW-1 and PS/MW-14) and decreasing trends <br /> and non-detects (ND) for methyl tertiary butyl ether (MTBE) in two site wells. Based on an <br /> anticipated continued use of the area as an industrial facility and a lack of drinking water <br /> receptors. NuStar recommends the following: <br /> • conducting one additional year of quarterly MNA analyses and then re-evaluating this <br /> monitoring frequency, <br /> • installing an additional B-zone well to better assess the presence of pollutants in the B- <br /> zone and evaluate MNA progress in that zone, and <br /> • developing a contingency plan that could be implemented in two to three months if future <br /> monitoring suggests that MNA is no longer effective. <br /> California Environmental Protection Agency <br /> pia Kec.yc(ed Paper <br />