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Page 5 September 11,2023 Brusca File No. 260-004 Anderson Barngrover Ranch Following a minimum two-hour equilibration period, and prior to purging and sampling, a shut-in test was conducted to check for leaks in the above-ground sampling system. A valve was installed in the probe tubing that exited the ground at the probe; this valve was left in the closed position during the shut-in test. The flow-control manifold for the probe was connected to the tubing after the valve, and the sampling canister was connected to the flow control manifold with the manifold valve also in the closed position. The above-ground system for the probe was evacuated to approximately 20 pounds per square inch using an air pump connected to the sampling system. The vacuum at the probe was monitored for at least two minutes and no loss of vacuum was observed at any of the probes during the shut-in tests. Following the shut-in test, the soil gas sampling assembly was purged with an air pump to remove stagnant or ambient air and to confirm that low-flow conditions do not exist. The purging flow rate was controlled to a maximum purge rate of 150 milliliters (ml) per minute. Following the purging of a minimum of three volumes, a soil gas sample was collected from the probe in a laboratory-provided, one-liter Summa canister. The collection of the soil gas sample was controlled using a laboratory-supplied vacuum gauge and flow controller(maximum rate of 150 ml per minute) attached to the sampling train. A leak check gas and shroud were used during soil gas sample collection to evaluate sample integrity (i.e., to determine whether ambient air was introduced to the soil gas sample either by leakage in the fittings in the sampling apparatus or advection through voids in the probe packing material). Prior to soil gas sample collection,a shroud was placed over the ground surface covering the sampling probe and the sampling assembly. A leak check gas(1,1 difluoroethane [DFA])was introduced beneath the shroud during sampling. Additionally, a sample of ambient air was collected beneath the shroud; this sample (identified as SHROUD) was analyzed to evaluate the 1,1 DFA concentration within the shroud for the purpose of determining the significance (i.e., percentage) of any 1,1 DFA leakage detected in the soil gas sample. As shown on the attached laboratory report,the soil gas sample did not contain the leak check gas 1,1 DFA at a concentration above the laboratory reporting limit. As such, the tracer gas testing does not indicate that unacceptable leakage occurred during sampling of the soil gas probe. The shroud sample contained 1,1 DFA at a concentration of 34,000,000 ug/m3. Following the soil gas sampling, the Summa canister was disconnected from the tubing and the tubing was removed from the sampling hole. Subsequently the soil gas probe hole was over-drilled and backfilled with neat cement grout in accord with SJCEHD requirements. LABORATORY TESTING The collected soil and groundwater samples from the borings were submitted to Sunstar Laboratories, Inc. for analysis for gasoline, diesel, and motor oil-range petroleum hydrocarbons by EPA Method 8015B and volatile organic compounds (VOCs) EPA Method 826013, including the fuel oxygenate MTBE. The collected soil gas sample was submitted to Eurofins/Air Toxics for analysis for VOCs (including the tracer gas 1,1 DFA) by EPA Method TO-15 and oxygen by ASTM Method D 1946. The soil and groundwater analytical data are summarized on Tables I and II, respectively. The soil gas analytical data are summarized on Table III. The laboratory reports