SITE INFORMATION AND CORRESPONDENCE FILE 1

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CLEARWATIER G R O U P, I N C. DP �� Ms. Mary Meays May 1, 1995 Senior Lead REHS MAY 0 11995 San Joaquin County Public Health Services Environmental Health Department ENVIRONMENTAL HEALTH P. O. Box 388 PERMITISERVICES Stockton, CA 95201-0388 Re: Ruiz Grocery Store, 4491 West Durham Ferry Road,Tracy Dear Ms. Meays, Enclosed please find a copy of the Quarterly Monitoring Report generated for the referenced location. Sampling results presented in the report are generally consistent with previous monitoring events. As I indicated in my recent telephone message, we are in the final stages of preparation for the scheduled aquifer/vadose zone testing. Prior to the commencement of this testing I felt it prudent to complete two limited preliminary tests. These tests included a step drawdown test using the new groundwater extraction well and the measurement of oxygen concentrations in soil vapor collected in previously constructed vapor extraction wells. The step drawdown test indicated that the pumping test may need to be completed with a vacuum applied to the extraction well, as the well pumped dry very quickly and little recharge was observed over the following hour. The vapor monitoring indicated the presence of an oxygen-poor vadose zone, suggesting that an extended vapor extraction test may be necessary in order to achieve optimum results. I am currently working with this new information, and will transmit a final plan of action and schedule within the next few days. Please do not hesitate to contact me if you have any questions or comments regarding scheduling or technical direction. I look forward to speaking with you again soon. Regards, _ Clearwater Group, Inc. Markus . Niebanck, R. G. Operati ns Manager CC. Ms. Brooke Birkie,Neumiller&Beardslee Ms. Stella Ruiz 1125 Atlantic Avenue 9 Suite 102•Alameda•California•94501 • (510)337$730•Fax(510)523-0984