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Project Number 2098RV45 November 30 2017 well logs will be included in the subsequent status report. 4.3 Soil-Gas Monitoring Parameters 4.3.1 Equilibration Time Following the installation of the VP well, subsurface conditions will be disturbed. As delineated in the DTSC document, Advisory - Active Soil Gas Investigations, to allow subsurface conditions to equilibrate, the purge volume test, leak test, and soil-gas sampling will not be conducted for at least 48 hours following installation of the temporary soil vapor monitoring wells. 4.3.2 Purge Volume To ensure that stagnant or ambient air is removed from the sampling system and to assure samples collected are representative of subsurface conditions, E2C or GSI will purge three (3) casing volumes from each VP well. Based on a well diameter of 2 inches, a filter sand pack and 12 inches in height layer of dry bentonite of 12 inches in height, and a porosity of 30%, E2C estimates that one (1) casing volume will be approximately 400 milliliters. Therefore, three (3) casing volumes would equate to approximately 1200 milliliters. However, the specific purge volume will be calculated for each soil vapor probe based on the volume of soil and dry bentonite plaed in tbe boring and a porosity of 30%. At a purge rate of 200 ml/min, purging accomplished in approximately 6 minutes. E2C will use a purge pump, calibrated to pump 200 milliliters per minute. The purge pump will not be used for sampling purposes. 4.4 Shut-in Test Prior to purging, a shut-in test will be performed to confirm the absence of leaks in the above ground sampling equipment. The shut-in test will be performed by evacuating the above ground fittings with a sampling pump to at least 100 inches of water. The vacuum will be monitored for at least 2 minutes with a pressure gauge sensate to 0.5 inches of water. If the vacuum is not maintained for 2 minutes, the above ground fittings will be adjusted and the test repeated. 4.5 Leak Test Leakage during soil gas sampling may dilute samples with ambient air and may produce results that underestimate actual site concentrations or contaminate the sample with external contaminants. Leak tests will be conducted to determine whether leakage is present (e.g., the leak check compound is detected and confirmed in the test sample after its application). 4.5.1 Leak Test Frequency Leak tests will be conducted at every SGA well location. 4.5.2 Leak Check Compounds The tracer compound isopropyl alcohol will be used as leak check compounds. A detection limit (DL) of 0.025 µg/L or less can be achieved. I1 EX Remediation