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Site Investigation Work Plan Carousel Cleaners, Sacramento, California Sampling and Analysis 4.2.2 Laboratory Analysis Samples will be analyzed for selected VOCs by U.S. Environmental Protection Agency(USEPA)Method TO-15 selective ion monitoring(SIM), as shown in Table 1. 4.3 Indoor Air Sampling Indoor air sampling will be conducted to assess whether VOCs in the subsurface have intruded into the indoor space and if they pose a significant risk to occupants. 4.3.1 Indoor Air Sample Collection Indoor air sample collection will be performed as follows: • A laboratory-supplied flow controller will be connected to a laboratory-supplied, 6-liter certified clean canister. The flow controllers will be set for an approximately 24-hour sampling period. The ambient air(outdoor background) sample also will be collected over a 24-hour sampling period, corresponding to the commercial primary sample locations. The canisters will be evacuated by the laboratory to more than 25 inches of mercury gauge pressure,before sampling. • The certified clean canisters will be placed at the interior locations at a height of 3 to 5 feet, or the average height of breathing zone for adults. • The valve on each canister will be opened to begin sample collection. The initial vacuum pressure indicated by the canister pressure gauge will be recorded on the chain-of-custody form. • After approximately 24 hours,when the vacuum gauge pressure is between 1 and 10 inches of mercury,the valve on the canister will be closed to end sample collection. The final vacuum pressure indicated by the canister pressure gauge will be recorded on the chain-of-custody form. • Duplicate indoor air samples will not be collected. • On completion of sampling, all indoor air sampling equipment will be removed. 4.3.2 Laboratory Analysis Samples will be analyzed for VOCs by USEPA Method TO-15 SIM, as shown in Table 1. 4.4 Soil Gas Sampling DP technology will be used to advance boreholes at 10 locations,to a maximum depth of 20 feet bgs. Figure 5 shows the locations of each soil gas well. Hand augers will be used for the first 5 feet,to clear the area of subsurface obstructions before drilling. 4.4.1 Drilling At each boring,concrete coring will be conducted(if required),to allow access to the subsurface. DP drilling equipment will be advanced to a maximum of 20 feet bgs. Continuous soil cores will be collected 4-2