SITE INFORMATION AND CORRESPONDENCE FILE 2

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Former George's Service Page 2 of 3 1600 Durham Ferry Road December 1, 2014 Tracy, California 95376 • Groundwater analysis and depth-to-water measurements: MW-1, MW-2, MW-7, MW-8, OW-1 and OW-2 (TPHg, BTEX, MTBE, and 1,2-DCA by EPA method 8260B) Ground Zero has recommended that this current monitoring and sampling schedule continue through the third quarter of 2015 at which time Ground Zero has proposed a future schedule beginning the fourth quarter of 2015. In the Work Plan, Ground Zero proposes: 1. Changing the sequence of air sparging (AS) to the following order: OS-1, OS-2, AS-3, AS-1, AS-6, AS-5, and AS-2 for twenty minutes each followed by a thirty-minute delay prior to starting the sequence again; Ground Zero believes that this will reduce the potential for prolonged groundwater mounding; 2. Alternating the soil vapor extraction (SVE) well configuration monthly and recording the order in the field log book; Ground Zero believes this will inhibit the creation of preferential pathways in the vadose zone; 3. Monitoring the performance of the AS system by monthly recording the pressure, flow and cycle time for each AS well; recording pressure readings from the compressor to the manifold; recording total operating hours and checking the air manifold for leaks and repairing, if necessary; quarterly inspecting the AS wellheads for leaks and repairing, if necessary; and semi-annually performing maintenance on the compressor; 4. Recording volatile organic compound concentrations with a photo-ionization detector (PID) at the influent, intermediate and effluent sampling ports while measuring air flow at the influent and effluent during monthly operation and maintenance of the AS/SVE system; 5. Collecting air samples quarterly at the influent for analysis by a California-certified laboratory for TPHg, BTEX, MTBE and 1,2-DCA; and collecting air samples at the intermediate sample port if significant concentrations of petroleum hydrocarbon contaminants are detected by the PID; 6. Conducting the pilot AS/SVE pilot test for one year; 7. Evaluating the effectiveness of the remediation system semi-annually and reporting the findings in the semi-annual groundwater monitoring and treatment system effectiveness report; and 8. Beginning the fourth quarter 2015, continuing quarterly performance monitoring of MW-1, MW-2, MW-7, MW-101, OW-1 and OW-2 while collecting depth-to-water measurements and groundwater samples for analysis during the second and fourth quarters as presented in the Work Plan.