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Site Investigation Work Plan Carousel Cleaners, Sacramento, California Sampling and Analysis from one of the locations for lithologic description. At the remaining locations, soil samples will be collected every 5 feet for lithologic description. Soil cuttings and cores will be screened using a photoionization detector(PID)to evaluate locations of elevated VOCs. Soil generated will be classified visually, in accordance with the Unified Soil Classification System (USCS) (ASTM 1985),and additional noteworthy observations will be recorded. Soil descriptions will include the following: moisture content, color, grain size(most abundant to least abundant), angularity, and other pertinent textural or mineralogical properties, and visual and/or olfactory indications of impact. Soil descriptions will be used to assess site-specific geologic and hydrogeologic properties. 4.4.2 Soil Gas Well Installation and Sampling Permanent SG wells will be constructed with well screens set at greater than 5 feet bgs and approximately 15 feet bgs, if possible. The wells will be constructed following guidelines contained in the Advisory— Active Soil Gas Investigations(DTSC 2015) (hereinafter referred to as the Advisory). In each borehole, duel nested SG probes will be placed within a 1-foot-thick sand pack. Approximately 1 foot of dry granular bentonite will be placed above each sand pack, and a new fill bentonite grout will be placed above the dry bentonite, extending to the sand pack above from the lower sampling depth and extending to ground surface from the upper sampling depth. Each soil gas probe will have small-diameter tubing (1/8 to 1/4-inch NylaflowTM or Teflon TM), extending to ground surface to enable sample collection from the desired depths.An example SG well construction specification is shown in Figure 6. Probe depths may be adjusted based on the field screening of continuous core samples and depth-to-groundwater at each location. After completion of drilling and well installation, a steel plate or other safety measure will be placed, and the newly installed SG wells will be allowed to equilibrate for at least 48 hours before SG samples are collected or when measurements show equilibrium. SG samples will be collected in accordance with the following procedures: • A shut-in test will be performed to check for leaks in the above-ground sampling train. The shut- in test will involve connecting a hand-vacuum pump with a built-in pressure gauge to the above- ground sampling train using flexible tubing, applying vacuum pressure of greater than 10 inches of mercury, and checking vacuum pressure after 1 minute has elapsed to verify that the vacuum pressure has not decreased by more than 5 percent. If the sample train fails the shut-in test,the fittings and connections will be tightened or replaced, and the shut-in test will be repeated. • A leak test will be performed with a gaseous leak-test compound, 2-propanol or isobutane,to check for leaks in the entire sampling system. The leak-test compound will be included in the analytes to be reported by the environmental laboratory. • The tubing exiting the ground surface at the SG probe will be connected to an electric vacuum pump or other type of pump,which will remove approximately three sample-train volumes of SG from the subsurface before sampling. The air flow rate during SG purging and sampling will be between 100 and 200 milliliters per minute, and the vacuum will be less than 100 inches of water. If the probe is found to hold a vacuum of at least 15 inches of mercury(200 inches of water) for at least 5 minutes, a wire will be used to attempt to unplug the probe. If this does not fix the problem,the probe will be removed,the hole will be plugged with cement grout, and a new probe will be installed at a new location within the sample area. 4-3