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Mr. Gerald Facino - 2 - December 4, 1990 <br /> For the Phase 1 investigation, one BAT probe will be installed adjacent to each of five groundwater <br /> monitoring wells previously installed (see "Monitoring Well Installation" report enclosed). <br /> Stratigraphic data provided during the installation of the BAT system will be compared to boring <br /> logs prepared from the previous well installation. Groundwater samples will be obtained from both <br /> the BAT system and the monitoring wells and submitted to a state certified analytical lab for analysis <br /> of gasoline compounds (EPA methods 8015 and 8020). In theory, the groundwater samples obtained <br /> by the BAT system should contain higher levels of volatile compounds than the samples obtained <br /> from monitoring wells using a bailer since the BAT system sampling method does not allow any <br /> losses due to volatilization. The method of sampling and other particulars should be made known <br /> in the workplan addendum. <br /> For the Phase 2 investigation,one BAT probe will be installed upgradient of the former underground <br /> tank pit along the western boundary of the site, and one BAT probe will be installed downgradient <br /> of the former underground tank pit on the opposite side of Plymouth Road from the site. These two <br /> locations had been proposed as locations for additional monitoring wells in the enclosed GTI <br /> workplan dated June, 1990. Phase 2, therefore, calls for installation of the BAT system in lieu of <br /> monitoring wells. Phase 2 is intended to exploit the capabilities of the BAT system in accurately and <br /> cost effectively determining the extent of groundwater contamination in a timely manner. The <br /> objective is to find the "ND line". If petroleum contaminants are detected from the downgradient <br /> BAT probe, then the probe can be removed and placed further downgradient until no petroleum <br /> contaminants are detected. It should be noted that in some cases the extent of investigation may be <br /> limited by above-surface structures or property access permission. <br /> Before field work can commence, a contract must be agreed upon by Chevron and Earth Technology. <br /> In order for Chevron to complete the contract, Earth Technology must submit a Certificate of <br /> Insurance as well as a price rate list and an itemized cost estimate for this project. <br /> If you have any questions or comments, contact Clint Rogers at (415) 842-8658. <br /> Sincerely, <br /> C.G. TRIMBACH <br /> By <br /> Clint B. Rogers 0 <br /> CBR/jsp:V 116 <br /> Enclosures <br /> c: Tom Peltier, Central Valley Regional Water Quality Control Board, Sacramento <br /> Gordon Boggs, Central Valley Regional Water Quality Control Board, Sacramento <br /> v/Margaret Lagorio, San Joaquin County Environmental Health, Stockton <br /> Joe Ramage, Groundwater Technology, Inc., Concord <br />