SITE INFORMATION AND CORRESPONDENCE

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`✓ N..W 27 March 1997 ARCO-Chevron Meeting Page 2 The Municipal Well #2 located in the Swenson Park Golf Course was drilled on April 23, 1959 to 252 feet bgs. The well is steel cased and is perforated between 85-90, 115-128, 150-155, 215-225 and 235-245 feet bgs. This well does not have a sanitary grout seal and is used infrequently. The City is obtaining surface water from Five Mile Slough to irrigate the golf course. The City of Stockton requested if at all possible that sampling by Chevron of the municipal wells be coordinated with City staff to coincide with their regular maintenance activities, since City staff will have to be on site when the water samples are collected. Chevron stated that a copy of the laboratory report with the analytical results of the samples collected from Municipal Well #10 will be forwarded to Ed Formosa. City of Stockton staff stated that the current depth to groundwater may not decrease as in past seasons because the City now provides water to the Lincoln Village Water District and uses primarily surface water sources rather than groundwater wells. Remedial Efforts ARCO had previously operated a groundwater extraction system that pumped up to 10 gallons per minute which was reduced to 5 gallons per minute when it was thought that perhaps the extraction system may be influencing an area larger than the ARCO plume. Approximately 18 months ago when vapor extraction and air sparge was started at the ARCO facility, the groundwater extraction well was no longer used for pumping. When the systems were first operated a 50 foot radius of influence was estimated with observed changes in dissolved oxygen extending 20 to 30 feet from the air sparge wells. Due to increases in the depth to groundwater, the vapor extraction well screened intervals are largely submerged and only low flow air sparging is in operation using an approximate flow rate of 3 cfm per well. Chevron is in the process of starting up the recently installed soil vapor extraction - air sparge remediation systems which are anticipated to be operational by April 4, 1997 and which consists of nine soil vapor extraction-air sparge dually completed remediation wells. Summary ARCO and Chevron will proceed with discussing a formal agreement related to the co-mingling of the groundwater plumes. If an agreement is finalized, an application with be submitted to the State Water Resources Control Board's Cleanup Fund to access the Co-Mingled Plume Account. ARCO has been submitting copies of reports to Chevron and will additionally submit copies of reports to Geraghty and Miller directly. Chevron will have Blaine Tech submit copies directly to ARCO and Brown and Caldwell. PHS/EHD will forward to Ed Formosa copies of correspondence directed to Chevron and ARCO. The City of Stockton will provide copies of the utility map for the intersection of Plymouth and Benjamin Holt to both Geraghty and Miller and to Brown and Caldwell. Additional monitoring which was agreed upon included Chevron's sampling of their air sparge wells to gather information to aid in their estimation of the vertical extent of their contaminant plume and ARCO's sampling of their monitoring well, PRI, at quarterly intervals. If you have any questions, or disagree with this summary, please contact me at(209) 468-0337. Donna Heran, REHS, Director Environmental Health Division Mary Meays, Senior REHS Margaret Lygorio, REHS Site Mitigation Unit Supervisor MM/ARCOCHEV.MGT cc: Elizabeth Thayer, CVRWQCB cc: Ed Formosa, City of Stockton cc: Steve Misner, Brown and Caldwell cc: Aaron O'Brien, Geraghty and Miller