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IA <br /> • r <br /> Date February 12, 1999 <br /> ARCO QUARTERLY GROUNDWATER MONITORING REPORT <br /> Facility No: 02186 Address: 3212 North California Street, Stockton, California <br /> ARCO Environmental.Engineer: Paul Supple <br /> Consulting CoJContact Person: . Pinnacle/Joel Coffman <br /> Consultant Project No: 20805-147.005 <br /> Primary Agency/Regulatory ID No: Carol Oz, San Joaquin County Public Health Services <br /> WORK PERFORMED THIS QUARTER (Fourth 1998): <br /> 1, Groundwater samples were collected and submitted for laboratory analysis from monitoring wells MW-1 <br /> through MW-4 and vapor well VW-3. Analysis included oxygenates by USEPA Method 8260. <br /> 2. As discussed with SJCPHS during the September 1998 meeting and as presented in Pinnacle's <br /> November 30, 1998, scope of work, Pinnacle collected a depth discrete water sample from MW-1 <br /> during the fourth quarter sampling event. The water sample was collected from the bottom portion of <br /> the screen interval by means of a discrete sampling device designed specifically to withdraw a sample <br /> • from a targeted sample depth. The purpose of this sampling approach was to assess dissolved hydro- <br /> concentration at a depth that coincides with historical low groundwater elevation and UST operation in <br /> an effort to evaluate if a submerged zone of soil impact is present beneath the USTs. <br /> 3. Pinnacle compiled and evaluated the groundwater monitoring data. <br /> WORK PROPOSED FOR NEXT QUARTER (First 1999): <br /> 1. Pinnacle will continue to perform quarterly groundwater monitoring. The next sampling event is <br /> tentatively scheduled for March 1999. Groundwater samples from wells MW-1 through MW-4 and vapor <br /> well VW-3 will be collected and analyzed for total petroleum hydrocarbons as gasoline (TPHG) using <br /> U.S. Environmental Protection Agency (USEPA) Method 8015 Modified; and for benzene, toluene, <br /> ethylbenzene, and total xylenes (BTEX) and methyl tert-butyl ether (MTBE) using USEPA Method 8020; <br /> and for oxygenates tertiary butanol, MTBE, di-isopropyl ether, ethyl tertiary butyl ether, and tertiary arhyl <br /> methyl ether using USEPA Method 8260. <br /> f <br /> CP1E:1ARC0121861QTRLY12186Q498.DOC-98V sg:1 <br />