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Heorot Power Holdings - 2 - 1 August 2018 <br /> • Dioxins and furans (EPA Method E1613 and SW8290) <br /> • CAM 17 Metals Total Threshold Limit Concentration (EPA Method 6010B/6020/207/208) <br /> Following completion of field work and evaluation of results, a report will be prepared and <br /> submitted to Regional Water Board staff that summarizes the scope of work, investigation <br /> results, recommendations, conclusions, maps, cross-sections, and an updated conceptual site <br /> model. <br /> Regional Water Board Comments <br /> 1. Evaluation of the direction and behavior of the groundwater gradient is important in <br /> understanding the direction of potential contaminant migration. Staff request installation <br /> of four piezometers across the site in order to determine groundwater gradient. The <br /> gradient piezometer investigation can be implemented concurrently with the <br /> magnetometer survey proposed in the Work Plan to select boring locations. <br /> 2. Prior to the selection of boring locations, the responsible party shall submit a plan of the <br /> site showing the former cogeneration facility layout, system components, equipment, <br /> and location of utilities including sewer connection and location of the wastewater <br /> storage vault. Ideally, this plan will be submitted as part of the Site Historical Activity <br /> Report and is important information to consider in selecting boring locations. <br /> 3. A total chromium concentration of 6.3 milligrams per kilogram (mg/kg) was detected in a <br /> soil sample collected on 17 January 2014. Although AGE indicated hexavalent <br /> chromium was not used as a descaling agent at the facility, the detection is at the <br /> industrial screening level for hexavalent chromium of 6.3 mg/kg. Hexavalent chromium <br /> should be included in the groundwater sampling analyses to clarify if the 17 January <br /> 2014 detection is indicative of hexavalent chromium levels at the site. The DI WETS soil <br /> analysis using EPA Method 6020 should also include hexavalent chromium to determine <br /> if soluble hexavalent chromium will leach out of the soil and negatively impact <br /> groundwater. <br /> 4. In the 4 August 2014 San Joaquin Valley Air Pollution Control District Title V Operating <br /> Permit for the former cogeneration plant, the Detailed Facility Report indicates that a <br /> natural gas fired gas turbine engine with ammonia injection was utilized at the facility as <br /> well as unidentified catalyst to induce selective oxidation and/or reduction chemical <br /> activity. The Operating Permit indicates use of ammonia injection, combustion emissions <br /> generation, and recent sampling data from the neighboring property show elevated <br /> detections of ammonia, nitrates, and total dissolved solids. Therefore, Regional Water <br /> Board staff request the addition of laboratory sampling analysis for ammonia as nitrogen <br /> (EPA Method 350.1), nitrate as nitrogen (EPA Method 300), and total dissolved solids <br /> (EPA Method 160.1). <br /> 5. Regional Water Board may request additional sampling analyses for soil and/or <br /> groundwater if review of the Site Historical Activity Report indicates additional <br /> constituents of concern (COCs) or other data gaps that aren't addressed in this Work <br /> Plan. <br />