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MEMORANDUM <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION <br /> 3443 Routier Road Phone: (916) 361-5600 <br /> Sacramento, CA 95827-3098 ATSS: 8-495-5600 <br /> TO: ANTONIA K. J. VORSTE FROM: ROBERT L. NIBLACK <br /> Senior Engineer / Engineering Geologist <br /> DATE: 26 October 1987 � <br /> SIGNATURE: y <br /> <�'� l <br /> SUBJECT: MOBIL FUEL TERMINAL, ROUGH AND READY ISLAND, SAN JOAQUIN <br /> COUNTY <br /> I have reviewed the report dated 26 August 1987 , which summarizes <br /> the t.-sks complete? to investigate ground �� .tcr gi_�l::ty ctt this <br /> site. My comments on that report follow: <br /> 1. The proposal to monitor the existing monitoring wells over the <br /> next six months should be implemented as proposed. We should be <br /> notified before the next round of samples is taken so we may <br /> have the opportunity to split samples for analysis. <br /> 2 . This report does not address the occurrence of the black oily <br /> substance in the tank A excavation. Further investigation will <br /> be required to locate the source of this contamination. It may <br /> be necessary to excavate the area around the new vapor dropout <br /> tank in order to sample and identify the contaminant, and aid in <br /> source determination. Mobil Oil recognized the possibility that <br /> this tank may have to be removed in their 28 April 1987 letter <br /> to the San Joaquin Local Health District. <br /> 3. Mobil Oil should submit a proposal to investigate the ground <br /> water quality in the area of tank B where soil samples were <br /> taken on 13 April 1987 . The present report does not address the <br /> potential for ground water contamination from this source. Soil <br /> contamination in the tank excavation showed this was a source of <br /> potential ground water contamination. Monitoring wells should <br /> be placed as close as is reasonably possible and down-gradient <br /> of the former tank location. <br /> 4 . Monitoring wells should also be constructed in the area which <br /> was used to infiltrate oil-water separator wastewater in the <br /> past. The goal is to determine how much impact this practice <br /> had on the quality of ground water. <br /> 5. Water level measurements in the wells should be calculated using <br /> mean sea level as the datum. <br /> 6. In the future, preparation of samples for analysis of purgable <br /> hydrocarbons (EPA Method 602) must be done by the purge and trap <br /> method (EPA Method 5030) . Results of analyses done on samples <br /> prepared by the headspace method (formerly EPA Method 5020) will <br /> not be acceptable. <br />