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1 <br /> ERI <br /> ENVIRONMENTAL RESOLUTIONS, INC. <br /> P-1, a_,,Y IV ED June 9, 1999 <br /> ERI 205503 R03 <br /> Mr Ed Ralston <br /> JUN 1U 1999 <br /> Tosco Marketing Company 1.)N jctq d l r\L r,EALTH <br /> ' 1380 Lead Hill Road, Suite 120 SERVICES <br /> Roseville, California 95661 �1r� IT I <br /> ' Subject Supplemental Evaluation of Groundwater, Tosco 76 Service Station 5886, <br /> 2701 West March Lane, Stockton, California <br /> ' Mr Ralston <br /> At the request of Tosco Marketing Company (Tosco), Environmental Resolutions, Inc (ERI) <br /> performed a groundwater investigation in the vicinity of the subject site The purpose of this work was <br /> to evaluate the lateral and vertical extent of dissolved hydrocarbons, including oxygenated compounds <br /> downgradient of the site The proposed scope of work was provided to the San Joaquin County Public <br /> Health Services, Environmental Health Division (the County) in ERI's Supplemental Evaluation of Soil <br /> and Groundwater Report, dated March 2, 1999 Tosco requested ERI to perform this investigation in <br /> response to a letter from the County that was not dated but was received (via facsimile) on <br /> ' March 26, 1999 (Attachment A) The County's letter approved the installation and the location of <br /> three off-site groundwater monitoring well clusters The County also requested Tosco to provide a <br /> Work Plan to further evaluate the lateral and vertical extent of dissolved hydrocarbons and oxygenated <br /> ' compounds detected in groundwater downgradient of the subject site At the request of Tosco, ERI <br /> submitted the Work Plan to the County on April 19, 1999 Specifically, the scope of work in this <br /> investigation included <br /> 1 • Obtaining an encroachment permit from the City of Stockton Public Works Department (the City) <br /> to install nine groundwater monitoring wells (three 3-well clusters) in the City's March Lane right- <br /> of-way, <br /> ' • Obtaining a permit from the County to install nine groundwater monitoring wells (three 3-well <br /> clusters, <br /> • Drilling nine off-site soil borings (B 11 through B 19), <br /> • Collecting soil samples from the deepest borings at each cluster location to evaluate soil <br /> stratigraphy, <br /> • Constructing groundwater monitoring wells MW8S/I/D through MW IOS/I/D in the borings, <br /> ' Developing monitoring wells MW8S/I/D through MW10S/I/D, <br /> • Measuring depth to water (DTW) in existing wells MW1 through MW7S/D and newly installed <br /> wells MW8S/I/D through MWIOS/IID, <br /> • Collecting and submitting groundwater samples from wells MW8SIIID through MWIOS/I/D for <br /> laboratory analyses for total purgeable petroleum hydrocarbons as gasoline (TPPHg), total <br /> extractable petroleum hydrocarbons as diesel (TEPHd), benzene, toluene, ethylbenzene, and total <br /> xylenes (BTEX), methyl tertiary butyl ether (MTBE), methanol, and ethanol, <br /> ' 73 Drgital Drive, Suite 100, Novato, Call/ornia 94949-5791 415-382-9105 (FAX 415-382-1856) <br /> Lake Forest • Novato • Seattle <br />