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5.0 SOIL GAS SAMPLING Soil Gas Investigations! The sample tubing will be connected to the syringe via a three-way valve. Each sample will be injected into the gas chromatograph/mass spectrometer(GUMS) for analysis within 30 Partner will perform soil gas sampling of the existing,newly installed,and replacement probes to evaluate minutes of sample collection. current soil gas concentrations at the She. The SVE system has been turned off since December 20,2019 As part of the laboratory QA/QC protocol,the mobile laboratory will collect and analyze instrument and and will remain off until after the sampling has been performed. Replicate soil gas samples will also be collected for quality assurance/quality control(QA/QC)purposes. sampling blanks to evaluate the potential for ctosscll also a call from the laboratory equipment and/or sampling materials Duplicate or replicate samples will alsobecollettedaM analyzed each day to evaluate 5.1 Soil Gas Sampling Methodology the precision of the mobile laboratory analysis. Each soil gas sample and QA/QC sample will be analyzed Soil gas samples will be collected in accordance with the July 2015 DTSC and Los Angeles Regional Water for VOCs and fuel oxygenates in accordance with EPA Method 82608 by the on-Site mobile laboratory. Quality Control Board(IARWQCB)'Advisory—Active Soil Gas Investigations.'Partner will subcontract with 5.2 Regulatory Agency Guidance Jones Environmental,Inc.(1g)to provide soil gas sampling and on-and off-Site mobile laboratory services. The mobile laboratory will be calibrated at the beginning of each day prior to the first sample analysis Partner will utilize the following regulatory screening levels for comparison of sample analytical results.Given Prior to purging and sampling the sub-slab and shallow soil gas probes,a shut-in test will be performed to the existing and foreseeable future use of the Site as a retail shopping center,the applicable screening levels check for leaks in the above ground finings The shut-in test will be performed on the above ground (SU)on-Site are those associated with commercialpndusbial land use.The results from the off-Ste probes on apparatus by evacuating the line to a vacuum of 100 inches of water, sealing the entire system, and Scarlett Placewill be compared to the more restrictive and protective residential screening levels The screening monitoring the vacuum for at least one minute A vacuum gauge attached in parallel to the apparatus will levels,for selected media are described below. be used to measure the vacuum. If any loss of vacuum occurs,the fittings will be adjusted as needed until April 20/9 DISC Human Health and Ecological Risk Office, Human Health Risk Assessment Note the vacuum does not change. Number3 Following performance of the shut-in test,a shroud consisting of a plastic tote or an overturned plastic five- The analytical results of soil gas samples, specifically, VOCs, will be compared to the commercial or gallon bucket will be used to cover the sample tubing that protrudes from the seal. A leak test will be residential screening levels,as approriate,listed in the April 2019 HERO Note 3. If VOCs are detected that performed to evaluate the integrity of the borehole seal at each of the S-toot depth soil gas probes A are not included in HERO Note 3, the May 2019 EPA Regional Screening Levels (RSLs)will be used for tracer gas mixture of mpemare,n-hexane,and n-heptane will be placed around each probe at the ground comparison. surface while sampling to evaluate the potential for ambient air intrusion. The tracer gas Is included on the list of target analytes. May 2079 United States Environmental Protection Ageny Regional Screening Levels Soil gas samples will be collected with a gas-tight glass syringe at a flow rate of approximately 200 milliliters per minute(ml/min)to reduce compound partitioning during soil gas sampling. The May 2019 EPA RSLs presented 1n the Generic Tables are chemical-specific concentrations for irdiAdual contaminants in air, drinking water and soil that may warrant further investigation or Site cleanup. The Gas-tight syringeswill be used to qualitatively evaluate whether a high vacuum soil condition is present No analytical results of soil gas samples,specifically,VOCs,will be compared to the applicable May 2019 RSLs flow,conditions occurwhen a sampling rate greaterthan 10 ml/min cannot be maintained without applying if these constituents are not included In DTSC HERO Note 3. a vacuum greater than 100 inches of waterto the sampling train. The sampling train is left at a vacuum for no less than 3 minutes. If the vacuum does not subside appreciably after 3 minutes,the sample location will be designated as no flow. Soil gas samples will be collected and analyzed byJEI,underthe oversight of Partner. The collected samples Will be transported to/EI's on-Ste mobile laboratory for analysis under chain-of-custody documentation. The mobile laboratory will be calibrated at the beginning of each day prior to the first sample analysis. A shut-in test(as described above)will also be performed to identify potential leaks in the sampling train prior to purging and sampling each probe. Approximately three probe volumes will be purged from the soil gas probes prior to sample collection in accordance with the July 2015 DTSC and IARWQCB'Advisory—Active Wanplan for Additional Soil Vapor Investigation PARTNER Tracy for Additional Soil Vapor InvestigationPARTNER Tracy Coni Shopping Center Tracy Corners Shopping Center 322S North Tracy Boulevam 3225 North Tracy Boulevard Tracy,California 95376 Trry California 95376 Febmary 1,2020 Febmaryl,2020 Page 8 Page 9