SITE INFORMATION AND CORRESPONDENCE FILE 2

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San Joaquin County DIRECTOR PQ W N Donna Heran,REHS Environmental Health Department� ASSISTANT DIRECTOR 600 East Main Street Laurie Cotulla,REHS (Un): Stockton, California 95202-3029 PROGRAM COORDINATORS Carl Borgman,REHS C •: P Mike Huggins, REHS,RDI Website: www.sjgov.org/ehd Margaret Lagorio,REHS Phone: (209) 468-3420 Robert McClellon,REHS Fax: (209)464-0138 ,teff Carruesco,REHS,RDI Kasey Foley, REHS STEPHANIE FURGAL OCT 0 3 2007 CHEVRON ENVIRONMENTAL MANAGEMENT COMPANY 6001 BOLLINGER CANYON ROAD, ROOM K2240 SAN RAMON CA 94583 RE: Former Chevron Service Station 9-0557 139 South Center Street Stockton, California By letter dated November 7, 2006, San Joaquin County Environmental Health Department (EHD) approved work plan titled Revised Work Plan for Monitoring Well Installation dated October 24, 2006, prepared by Blasland, Bouck & Lee, Inc. (BBL) on your behalf. On January 2, 2007, EHD issued permit number 0049279 for the installation of one deep monitoring well (MW-18D2) with a screen interval between approximately 110 and 115 feet below surface grade (bsg). To date, this deep monitoring well has not been installed. As nearly a year is more than enough time to schedule and implement such a simple work plan, you are directed to have the work scheduled with this office by November 9, 2007, with the work to be completed within the following 45 days and a report of findings submitted within 60 days of completion of the fieldwork. On July 2, and August 9, 2007, ARCADIS U.S., Inc (ARCADIS BBL) contacted EHD by telephone and recommended the destruction of monitoring wells MW-5, MW-7, MW-8, and MW-13 "due to health and safety concerns associated with traffic hazards". All four wells are located in the sidewalk several feet from the street curb and have been in place for more than five years. EHD will not approve removal of these four wells; however, EHD has reviewed the analytical results for groundwater samples collected from all monitoring wells associated with this site and EHD believes a reduction in collecting groundwater samples from MW-5, MW-7, MW-8, MW-13, MW-14, and MW-17 from quarterly to annually appears to be adequate to track the plume and will approve such a reduction if requested. However, the EHD will still require you to continue to monitor water levels in these wells to determine groundwater gradient and inferred flow direction. Monitoring wells MW-15, screened between 20 and 30 feet below ground surface (bgs), and MW-15D, screened between 46 and 51 feet bgs, have consistently dewatered while being purged during the quarterly groundwater monitoring since June 2006. Depth to groundwater has typically been approximately 21.5 feet bgs. Also, it is documented in previous quarterly groundwater monitoring reports as early as August 2005 that MW-15D had been severely damaged and the well cover was missing.