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Memorandun, CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD . CENTRAL VALLEY REGION 3201 S Street Sacramento, California 95816 Phone: 445-0270 TO: Ton Vorster FROM: Gary Reents Senior Engineer Area Engineer DATE: 7 September 1984 SIGNATURE: SUBJECT: GROUND WATER MONITORING AT SMS BRINERS, SAN JOAQUIN COUNTY Luhdorff & Scalmanini (L&S), responding for SMS Briners, outlined their plans for implementing ground water monitoring in a 21 August 1984 letter. L&S proposes to bore three holes along opposite sides of the ponds to investigate surface soils and the underlying clays and gravels. Unsaturated zone monitoring equipment will be installed in each hole. Secondly, a single 125 to 150 foot deep monitoring well is proposed at the northwest corner of the ponds. An existing upgradient well will be used to obtain background samples. Based on this letter and a 29 August telecon with Joe Scalmanini , I have the following comments: 1 . Installing unsaturated zone monitoring equipment in bore holes adjacent to the ponds (the map attached with the L&S letter shows the proposed bore holes being up to 150 feet away from the pond edges) may not prove effective monitoring. If monitoring equipment is placed in the shallow portion of the holes they may not intercept any leakage because of insufficient lateral spreading. If the equipment is placed deeper in the holes where leakage probably would be intercepted the pollution will already be near or at the water table. The proposed bore holes would best be used to define shallow lithology and for locating the ground water table and gradient by installing piezometers. Any unsaturated zone monitoring equipment should be placed directly beneath the ponds which is not feasible at this time. 2. Installing only one monitoring well , and at a prespecified depth of 125 to 150 feet, will probably not provide effective ground water monitoring. First ground water, which is normally about 50 to 60 feet in the area, should be monitored to ensure early detection of contamination. Additionally, the depth, location and number of monitoring wells should be based on the ground water gradients and physical properties of the aquifer. A ground water monitoring well network must be able to detect any contami- nation emanating from the ponds. 3. L&S states that due to the high sodium content of the wastewater brines any leakage would rapidly destroy the permeability of underlying clays and prevent further leakage. Though L&S is correct about the effects of sodium on clay soils, high aqueous salt concentrations will , conversely, increase clay permeabi,lities. Permeability changes are also highly dependent on the