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C-LEAR WATE MAY 17 1995 <br /> G R O U P, I N C. ENVIRpNMINTAL HEALTH <br /> pERMIl J SERVICES <br /> Ms. Mary Meays May 16, 1995 <br /> Senior Lead REHS <br /> San Joaquin County Public Health Services <br /> Environmental Health Department <br /> P. O.Box 388 <br /> Stockton, CA 95201-0388 <br /> Re: Ruiz Grocery, 4491 Durham Ferry Road, Tracy <br /> Dear Ms. Meays, <br /> I am glad we had a chance to touch base yesterday regarding the upcoming pilot <br /> testing activity. In accordance with our discussion, the following provides the <br /> information you requested regarding recent pre-testing and the modifications to the <br /> actual test. <br /> Development Conducted During Recovery Well Installation <br /> Minimal development was accomplished immediately following the installation of <br /> the recovery well: What development was accomplished was completed by means <br /> of hand bailing. <br /> Yield Testing <br /> As we discussed, the yield test described in recent correspondence indicated that the <br /> new recovery well would not produce a sustained flow of water under testing or <br /> production conditions. Depth to water in the recovery well was measured to be <br /> approximately 17.20 feet below ground surface. The completed depth of the well is <br /> 30 feet below grade. The lowermost three feet of the well contained fine-grained <br /> sediment, likely residual fines from previous bailing. Accounting for a 2-inch <br /> diameter well annulus (assuming 25% porosity of filter pack) and the measured 10 <br /> feet of standing water in the 4-inch diameter well, a volume equal to about 26.5 <br /> gallons of water was available for removal. Thin corresponds to the amount of <br /> water recovered. Approximately 0.5 gallons of water recharged to the well after 30 <br /> minutes. <br /> These observations are not entirely inconsistent with recharge rates shown by some <br /> of the more shallow monitoring wells during sampling events. <br /> Vapor Testing <br /> Experience with previous pumping tests demonstrates that it is prudent to measure <br /> the concentration of oxygen in vapors in wells to be tested prior to testing, <br /> particularly if the vapors to be generated during testing are to be treated by an IC <br /> engine, as the efficiency of the combustion process is a function of oxygen <br /> concentration. To this end, Clearwater measured 02 concentrations in VW-1, 2, and <br /> 3, as well as in MW-2 and 7 with a GasTector 02CO2 meter. Concentrations of 02 <br /> 1125 Atlantic Avenue-Suite 102-Alameda*Califon-dao 94501 - (510)337-8730-Fax(510)523-0984 <br />