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$TG TF CIF CCI IFnRNIG F t 1 P .� • PFTF W11 CCW r;nvarnnr CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD "" w CENTRAL VALLEY REGION ENVIRONMENTAL HEALTH s e 3443 Routier Road, Suite A PFRMIT SFRVICE Q € Sacramento, CA 95827-3098 PHONE: (916) 255-3000 93 AUG I P ) 145 FAX: (916) 255-3015 16 August 1993 Mr. Nick Nickerson Unocal Corporation 2000 Crow Canyon Place, Suite 450 San Ramon, CA 94583 REVIEW OF "SOIL AND GROUNDWATER INVESTIGATION" REPORT Thank you for submitting the Soil and Groundwater Investigation report for the PureGro/Brea facility in Stockton. The report shows that four monitoring wells were installed and that soil and groundwater samples were analyzed, as per the approved workplan. This initial round of sampling shows elevated levels of 1,2-DCP and nitrate in the downgradient wells. The upgradient well also has elevated nitrate levels. Because gasoline, diesel, and oil were not detected in the groundwater, the Board will not require further characterization of the groundwater for these constituents. However, as agreed upon in the workplan, the groundwater must be sampled for the next four quarters. The initial samples were collected in May 1993; therefore, the remaining samples should be collected in August 1993, November 1993, February 1994, and May 1994. Samples must be analyzed for 1,2-DCP, nitrate+nitrite, and TKN. In response to your question about the proper disposal of the drummed soil cuttings and purge water, the soil may be disposed of onto cropland. It must be applied at an agronomic rate, which in this case would be no more than 3" thick, and must be immediately incorporated into the soil. A crop should be planted soon afterward. The purge water from MW3 does not contain 1,2-DCP, so it too may be disposed of onto cropland at an agronomic rate, and at a rate at which no tailwater leaves the land. However, the 1,2-DCP concentration in the purge water from the other three wells is too high to apply to cropland. You may either leave the water in drums onsite, or transport it to a facility which can treat the pesticide to levels which will not cause water quality or human health concerns. After you have disposed of the soil, and have decided what to do with the purge water, please submit a short letter report detailing the disposal methods. If you wish, this information may be included in one of the quarterly monitoring reports. If you have any questions, I can be reached at (916) 255-3104. WENDY WYELS�', Ag Regulatory Unit cc: Ms. Gail Holmes, Condor Earth Technologies, Turlock Mr. Michael Infurna, San Joaquin County Health, Stockton Mr. Jan Wagoner, Environmental Coordinator, Unocal, West Sacamento Ms. April Pearson, Counsel, Unocal, Los Angeles