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STATE OF CALIFORNIA -EnvironmentalAtion Agency • PETE WILSON Governor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD CENTRAL VALLEY REGION 3443 Routier Road, Suite A Sacramento, CA 95827-3098 PHONE: (916) 255-3000 ti.,a,,,,,.J'� FAX: (916) 255-3015 14 March 1997 Ms. Martha Bowman Trustee, Cal Farm Supply P.O. Box 570 Penryn, CA 95663 CAL FARM SUPPLY. WORKPLAN APPROVAL Thank you for submitting the Workplan: Environmental Corrective Action for the former Cal Farm Supply facility at 2040 W. Washington Street, Stockton. The workplan is approved with the following comments and additions: . It appears that there's a groundwater mound in the southwest portion of the property. In order to learn more about the groundwater gradient in this area, I'd like the temporary well casings for geoprobes #7-10 to remain in the ground for several hours, and then the groundwater elevation measured. We could relate the elevations to a datum at another time, probably when the new wells are surveyed. . There is known nitrate contamination at the property to the south of Cal Farm Supply, but the contamination doesn't extend as far east as Geoprobe sample #SB-10. In order to help define the zone of contamination, please move #SB-10 approximately 200-250 feet straight west of the proposed location. • The water from Geoprobe sample #SB-1 should also be analyzed for herbicides by EPA method 615. . Please consult with me before you decide on the final placement of the new wells. . The sampling program for the quarterly monitoring of the wells may need to be revised pending the results of the first quarter of sampling. Therefore, the first quarter monitoring report should also contain a proposed analytical schedule for subsequent monitoring events. . In Table 2, are the nitrate results reported on a nitrate basis or on a nitrate-nitrogen basis? In the future, please report all nitrate results as nitrate-nitrogen (NO3 N). . I think it would help in our understanding of the site to sample the existing monitoring wells at the same time that the Geoprobe samples are collected. However, I understand that you don't have the resources to do this. At this time, I will plan to meet you on site, and to collect samples from the wells for Board analysis.