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1 <br /> Ben Hall -2- 18 April 2011 <br /> Musco Family Olive Company <br /> with the aging liner system and presence of leachate in the sumps, we suggest that Musco <br /> conduct a thorough investigation of the ponds, including conducting a liner leak detection test <br /> and test of the LCRS. Once completed, the results will allow Musco to evaluate the liners and <br /> functionality of the LCRS, and begin the process of preparing for their eventual replacement, if <br /> necessary. <br /> 2. Concerns about Vadose Zone Monitoring System. <br /> The Detection Monitoring Program for the Class II Surface Impoundments is made up of <br /> unsaturated zone monitoring that utilizes suction lysimeters set at five and ten foot depths and <br /> groundwater monitoring wells installed at various locations around the Class II ponds. <br /> During December 2010, Musco performed maintenance of the lysimeters in accordance with <br /> the manufacturer's recommendation. Most lysimeters now have higher "initial and residual <br /> vacuum" than reported during the June 2010 monitoring event. However, the capability of the <br /> lysimeters to operate effectively in the existing soil environment as a leak detection device <br /> beneath the ponds is still uncertain. Staff looks forward to Musco's evaluation of the lysimeter <br /> maintenance in the upcoming Well Installation Report and subsequent semi-annual monitoring <br /> reports. <br /> 3. Adequacy of Detection Monitoring Program. <br /> Additional groundwater monitoring wells have been installed around the ponds. The additional <br /> wells will provide a higher level of capability to detect a leak than previously existed. However, <br /> staff is concerned about groundwater elevations in well MW-12, which appear to be <br /> decreasing to a point where the well is not able to provide water quality samples. Well MW-12 <br /> is an integral part of the detection monitoring program and deepening this well into the <br /> intermediate zone should be considered to close the data gap in the northwest corner of the <br /> ponds. We can discuss this further after we review the forthcoming monitoring well installation <br /> report. <br /> 4. Evidence of a Potential Release <br /> Water quality samples were collected from wells MW-10R and MW-22 only. MW-12 was not <br /> sampled because of a lack of water, but prior data were also reviewed. The report indicates <br /> that sodium and chloride increased in well MW-22, and that these constituents decreased in <br /> well MW-1 OR, which is the only background well. The report also provides Stiff and Piper <br /> Diagrams to illustrate the point that increasing concentrations of well MW-22 is not due to a <br /> release from the ponds. The waters plotted indicate the pond water is sodium, potassium, <br /> chloride dominant; well MW-22 is also sodium, potassium, chloride dominant; well MW-1 OR is <br /> sodium and potassium dominant. On the anion side, well MW-10R actually has no dominant <br /> type. It falls below the 50% chloride line (this is likely due to the bicarbonate concentration <br /> that is almost two times that of MW-22). However, on the anion side of the Piper Diagram, well <br /> MW-22 actually lies between well MW-1 OR and the pond water as would be expected when <br /> California Environmental Protection Agency <br /> eaRecycled Paper <br />