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MEMORANDUM _ n CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 255-3000 Sacramento, CA 95827-3098 CALNET: 8-494-3000 TO: Gordon L. Boggs FROM: Elizabeth A. Thayer UGT Program Coordinktor Associate Engineer DATE: 9 December 1994 SIGNATURE: � .LZ.Ct SUBJECT: REVISED MONITQRING AND REPORTING PROGRAM, GEWERE, 16 SOUTH CHEROKEE LANE, LODI, SAN JOAQUIN COUNTY Geweke submitted the quarterly report on 20 October 1994 as required in C&A No. 93-701. The report contained the first analytical results from the site after full-scale inoculation, which occurred on 16 August 1994. On 12 October 1994, the draft Revised Monitoring and Reporting Program (RMRP) was sent out for comment and on 31 October 1994, Geweke submitted their suggested changes by fax. The following comments on the quarterly report and Geweke's suggested changes are reflected in the final RMRP. Comments on Ground Water Contamination Geweke had previously requested that lead and EDB analyses be deleted from the ground water monitoring. You and I agreed, and Geweke dropped them from future monitoring. However, on review of the recent quarterly report, MW14 has had consistent EDB contamination. Therefore, EDB monitoring of MW14 should be reinstated. Lead was detected on several occasions, at concentrations below the MCL of 50 µg/1, in a number of wells. The highest concentration was 21 µg/1. I recommend that lead be dropped from monitoring program. DCA has consistently been detected in EW1, MW13, and MW14 and has been detected on several occasions in MW7, MW8, and MW9. Chloroform was recently detected in MW7, MW14, and EWl. Geweke requested to delete monitoring of halogenated solvents from wells MW6, MW10, MWll, and MW12 because none has never been detected in those wells. I concur with MW6 and MW10 because they are upgradient. MW11 and MW12 are both downgradient. I think at least one of these wells should continue to be monitored, I recommend MW12. HVOC's will continue to be monitored in the other monitoring wells. It appears that the plume may be spreading. Concentrations in MW6, upgradient, have increased for the last 3 quarters, from 80 to 1100 ppb TPHg and MW6 had benzene, at 22 ppb, for the first time. MW10, a crossgradient well, has shown contamination for the last 4 quarters. Previously it had several quarters of ND. MW11, downgradient, has also had contamination for the last 4 quarters. Previously it had several quarters of ND. Ground water extraction for plume control appears necessary.