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• MEMORANDUM • ,CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRA F oAe :LEY 36EGGI�ON 3443 Routier Road, Suite A ATSS Phone: 8-495-5600 Sacramento, CA 95827-3098 FROM: Wendy Wyels Ag Regulatory Unit T0: Rudy Chief Ag Regulatory Unit Wendy Cohen, Chief Well Investigation Unit DATE: 21 August 1991 SIGNATURE: SUBJECT: REVIEW OF THE PHASE II ASSESSMENT FOR BREA AG, STOCKTON; SUMMARY OF MEETING Report Review Brea Ag's consultants, Kleinfelder, have submitted a "Phase II Soil and Groundwater Assessment Report" for the Brea Ag facility in Stockton. Construction activities (for a new liquid fertilizer containment area) began at the site last fall . Because three dry wells were found where the new concrete pad was to be poured, soil samples were taken. Construction work stopped, and additional samples (from three borings) were collected in April . Because the April soil samples contained elevated levels of DDT, ;i nitrogen, and 1,2-dichloropropane (1,2-DCP) , Brea Ag asked Kleinfelder to do additional investigative work. The Phase II investigation encompassed the drilling of two deep soil borings, sampling groundwater with a BAT probe, and sampling Brea Ag's domestic well . All field work and analytical work appears adequate. The soil samples show decreasing amount of nitrate, and total Kjeldahl the highest concentrationstions of nitrate was from 31- nitrogen (TKN) with depth, although 61' below ground surface. ntered at 78' , the borings were advanced to 81' and Although groundwater was first encou 911 . Nitrate-nitrogen was detected at concentrations of 1T2.8 andhe 20.7 pfor bothDabo e the MCL of 10 ppm. 1,2-DCP was found at 27 and 8.8 ppb is 5 ppb; however, EPA's 1-in-a-million cancer risk estimate is 0.5 ppb. There are two errors in the "Conclusions and Recommendations" section of the report. 1 . Kleinfelder states that there is "a proposed MCL of 0.5 ug/l for 1,2-DCP in drinking water . According to Dr. Jon Marshack, and his "Water quality Goals" booklet, the EPA primary MCL goal for 1,2-DCP is 5.0 ppb, and the EPA 1 . In million cancer risk is 0.5 ppb. These numbers have been b�numberdwould be used setting clean-up goals for the groundwater basin, the 0.5 pp because our Basin Plan states that there be no toxicity in groundwater, and DHS has determined that cancer risk numbers are equated with toxicity. 2. Kleinfelder states that "TKN is the total amount of nitrogen available in a given sample. This is not correct. According to "Standard Methods," the TKN analysis determines nitrogen forms in the trinegative state, and does not take into account nitrate, nitrite, nitrile, and other more esoteric forms of nitrogen. Therefore,