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Pacific Gas and <br /> &i f/ectiic Company <br /> Technical and Ecological Services 3400 Crow Canyon Road <br /> San Ramon,CA 94583 <br /> — ' 92582112001 <br /> March 15, 1999 <br /> Mr.Kit Custis <br /> California Regional Water Quality Control Board <br /> Central Valley Region <br /> 3443 Routier Road, Suite A <br /> Sacramento, California 95827-3003 <br /> Re: Demonstration Study for Enhancing Subsurface Biodegradation Rates Using Regensis®Oxygen <br /> Releasing Compound,PG&E's McMullin Gas Dehydrator Station <br /> Dear Mr. Custis: <br /> Please find enclosed the above referenced report for your review. As you are aware,the McMullin Gas <br /> Dehydrator Station was one of three sites selected by PG&E in 1998 for conducting Research and <br /> Development demonstration projects to determine the efficacy of three different in-situ biological <br /> treatment methods for accelerating the degradation of petroleum hydrocarbons. A compound formulated <br /> by Regensis®called Oxygen Releasing Compound(or ORC)was injected in the subsurface at the <br /> McMullin Gas Dehydrator Station in the areas impacted by petroleum hydrocarbons. ORC reportedly <br /> releases oxygen when placed in contact with water and as such,this R&D project was designed to <br /> determine if injecting ORC the subsurface would result in increased microbial activity and higher <br /> biodegradation rates of petroleum hydrocarbon compounds. <br /> For this R&D demonstration project, concentrations of petroleum hydrocarbons were tracked in soil and <br /> groundwater over several months before and after the injection of ORC. The soil samples were analyzed <br /> for TPH and BTEX, and the groundwater samples were analyzed for TPH,BTEX,and several <br /> geochemical parameters that are indicative of microbial activity(i.e., dissolved oxygen, carbon dioxide, <br /> and oxidation-reduction potential). The progress sample results were compared to the baseline data to <br /> evaluate the effectiveness of the ORC injection: <br /> As summarized in the enclosed report,the concentration of TPH in soil and groundwater varied <br /> considerably in samples collected both before and after the injection of ORC. As a result, it is difficult to <br /> determine whether the ORC increased biodegradation rates. The levels of gasoline- and diesel-range <br /> hydrocarbons in groundwater decreased after the ORC was injected,but BTEX concentrations did not <br /> decrease in a similar fashion. The groundwater geochemical results(particularly carbon dioxide)suggest <br /> that microbial activity increased during the monitoring period,which may indicate that TPH <br /> biodegradation rates increased. Because the conclusions derived from this R&D project are results are <br /> somewhat unclear,the report recommends additional monitoring of both soil and groundwater over the <br /> next few months. <br />