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California Regional Water Quality Control BoardQ k_�%j a <br /> Central Valley Region <br /> m; Karl E.Longley,ScD,P.E.,Chair <br /> Linda S.Adams Arnold <br /> 11020 Sun Center Drive#200,Rancho Cordova,Cali or�,ia?7 1 <br /> Sec,enn or Schwarzenegger <br /> Secre <br /> Environmental Phone(916)464-3291 -FAX(916)464 CE����� <br /> http://www.waterboards.ca.gov/centralvaiiey <br /> Gorernur <br /> Protection <br /> AUG 1 .9 2009 <br /> 17August 2009 E'''' `!TH <br /> Mr. Tim Van Domelen <br /> Manager, Environmental Health, Safety, and Security <br /> J. R. Simplot Company <br /> 16777 Howland Road <br /> Lathrop, CA 95333-0198 <br /> UNDERGROUND STORAGE TANK GROUNDWATER WELL SAMPLING — J.R. SIMPLOT <br /> COMPANY, 16777 HOWLAND ROAD, LATHROP, SAN JOAQUIN COUNTY <br /> The Central Valley Regional Water Quality Control Board (Central Valley Water Board) staff <br /> have received the Underground Storage Tank Groundwater Well Sampling Report (Report), <br /> dated 31 July 2009, submitted on behalf of J. R. Simplot by AMEC Geomatrix, Inc. In the <br /> Report, AMEC Geomatrix describes the field activities, data collection, and results of <br /> groundwater sampling conducted in June 2009 at the J.R. Simplot facility at monitoring wells <br /> MW-2 and MW-3. The wells are located in the vicinity of the former petroleum underground <br /> storage tanks (USTs) that were removed in 1982 and 1988. Of the three monitoring wells <br /> installed April 1989 near the tank pit, monitoring well MW-1, could not be located for the June <br /> 2009 sampling event. <br /> No floating petroleum product was observed during monitoring well sampling. Groundwater <br /> was analyzed for total petroleum hydrocarbons as gasoline (TPHg) and as diesel (TPHd), <br /> benzene, toluene, ethylbenzene, xylenes (BTEX), 1,2-dibromo, 3-chloropropane, and ethylene <br /> dibromide. TPHg and benzene were present in monitoring well MW-2 at 1,400 and 520 <br /> micrograms per liter (pg/L), respectively. These concentrations indicate an impact to <br /> groundwater in this area from the former underground storage tanks. <br /> In the Report, AMEC Geomatrix states that the total concentration of BTEX has decreased in <br /> well MW-2 from about 1,930 to 691 pg/L since 1989. They further state that "natural <br /> attenuation processes should result in effective cleanup of the dissolved petroleum <br /> hydrocarbons in the vicinity of the USTs site well before the Occidental plume is remedied." <br /> No follow-up actions are recommended. <br /> I have reviewed the Report and have the following specific comments. <br /> 1 . In the Underground Storage Tank Site Closure Work Plan (Work Plan), AMEC Geomatrix <br /> stated that because the soils in the vicinity of the USTs had been characterized in 1989 <br /> and concentrations of petroleum compounds have likely decreased since that time, they <br /> do not believe that soil sampling is warranted, "unless significant detections of BTEX are <br /> found in groundwater samples from wells MW-1, MW-2, and MW-3." The <br /> aforementioned occurrence of benzene in well MW-2 is significant and warrants further <br /> California Environmental Protection Agency <br /> Z5 Recycled Paper <br />