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DocuSign Envelope ID:6CF06457-7118-4304-9934-67C64310797A <br /> Proposal for RI—Additional Groundwater, Landfill Gas and Soil Characterization <br /> ANEW <br /> Hillsborough Dump <br /> ID No. NONCD0000483 <br /> Task Orders 483DP-15, 16, 17 and 18 <br /> S&ME Project No. 4305-17-061 F <br /> quality control (QC) duplicate samples (one for VOCs/methane and one for hydrogen sulfide)will be collected <br /> concurrently. <br /> Sample trains will be used that include Teflon tubing, rotometer,valves,gauges,tubing fittings,flow control valve <br /> and sample canisters. After each sampling train is connected,a leak tightness check will be conducted prior to <br /> sample collection. <br /> Vacuum- Leak Tightness Check: <br /> Close the valve at the top of the PVC landfill gas probe. <br /> Ensure that all connections are made,and valves are in correct positions to allow flow from only the <br /> sample train into the sample canister.There should be no flow from the landfill gas probe or from <br /> ambient air sources. <br /> Open the valve to the sample canister to allow flow to the canister only(there should be no flow, as the <br /> valve to the landfill soil gas probe remains closed). <br /> Record the vacuum pressure on the gauge on the sample canister for at least three minutes. <br /> If a change of vacuum is recorded at more than +/- 5 mm of mercury, stop the leak check and check all <br /> fittings and adjust as needed. <br /> Recheck and readjust as needed to ensure that the sample train has no leaks and vacuum pressure <br /> changes are within +/- 5 mm of mercury or less. <br /> Collection of Landfill Gas Samples with Silonite and Summa Canisters: <br /> Batch-certified six-liter sample canisters under approximately 28—30 inches of mercury(Hg)vacuum will <br /> be provided by a North Carolina certified laboratory for sample collection. The laboratory will provide a <br /> pressure gauge and flow controller for each canister, and Swagelok type fittings with Teflon tape will be <br /> used.The flow controller will be set by the laboratory to collect landfill gas into the canisters at <br /> approximately 25 milliliters per minute(ml/minute). (A collection rate of 200 ml/minute or less is <br /> recommended to limit stripping of VOCs from the air samples). <br /> The canister valve and the valve at the top of the PVC soil gas probe will be opened to ensure that air flow <br /> is from the landfill soil gas probe (or flux chamber) into the sample canister only. It will take about three to <br /> four hours to sufficiently fill the sample canister. <br /> The sampling parameters will be recorded (e.g.time, rate, begin pressure, end pressure, etc.). <br /> When the sample canister is full,the valve on the canister will be closed and disconnected from the <br /> sampling train.The sampling train will also be removed from the landfill gas probe and a PVC cap will be <br /> replaced on the gas probe to close the probe. <br /> The Silonite and Summa canisters will be shipped under standard chain of custody to the laboratory for <br /> hydrogen sulfide analysis by EPA Method 15 and VOC analysis by EPA Method TO-1 5. <br /> Field Screening of Landfill Gas <br /> Upon completion of landfill gas sampling, S&ME will field-screen GP-6 for the presence of landfill gas. Prior to <br /> screening, S&ME will gauge depths to water(if any) in the probe. Portable meters will be used to collect the <br /> following parameters: <br /> December 17, 2020 4 <br />