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Cleanup in Vulnerable Communities'Initiative Final Project Reference:Bobson Cleaners Discovery and Enforcement Discovery Project Number:60688620-5.1 Investigation Work Plan 5. Soil gas samples will be analyzed with method TO-1 5, modified for air analysis as indicated in Programmatic QAPP.TO-15 analysis will be NELAP certified, and Method 8260 will be certified for water.The laboratory protocols for Method 8260 and TO-15 should follow the recommendations in Appendix F of the 2015 Soil Gas Advisory and the guidelines in SW-846. 6. Summa canisters will be batch certified for cleanliness. 7. All syringes and bulbs used for Method 8260 analysis will be constructed of glass (no plastic). 8. The soil gas samples will be analyzed for the full suite of analytes including, but not limited to, benzene, toluene, ethylbenzene,xylenes(BTEX), naphthalene,freons, PCE,TCE, and their breakdown products. 9. Analytical reporting limits should not exceed 0.5 lag/m3. 10. Soil gas samples will not be collected within 5 days of a rainfall event of more than a'/2 inch of precipitation. 11. If the analytical results of the soil gas sampling are below vapor intrusion screening levels,then an additional round of sampling will be conducted before risk-based decisions are made.The additional round of sampling should be collected in the opposite season (rainy versus dry). 3.2.5.3 Soil Matrix Sampling No soil matrix samples will be collected for laboratory analyses for this project. 3.2.5.4 Groundwater Sampling Based on information provided by the SWRCB online GAMA database groundwater depth near the Site was at approximately 14 to 24 feet bgs in 2006(SWRCB 2023). More recent groundwater depths were not found during the Phase I ESA for the site, actual groundwater depths cannot be determined without further site evaluation. Groundwater samples will be collected following the HydropunchT"^sampling technique (or equivalent). When collecting groundwater grab samples for the evaluation of potential impact of contaminant releases,the following should be considered: • The uppermost section of the shallowest water bearing unit should be subject to grab sampling. • Temporary well screens should be approximately 6 to 48 inches in length. Screens of 48 inches should be considered if low hydraulic conductivity is anticipated. • Specific to the grab sampling event only, groundwater samples should be collected with a bailer rather than with a pump. Groundwater samples will be collected in appropriate containers that contain required preservatives. In the case of samples collected for VOC analysis, the collected groundwater will fill the VOA vial until there is no headspace, and then the vial will be tightly sealed as soon as possible.The vial will be inverted and checked for air bubbles to ensure zero headspace. If a bubble appears, the vial will be discarded, and a new sample will be collected.All sample containers will be labeled, placed in Ziploc bags, and delivered to the ELAP-certified laboratory for analysis in properly chilled coolers with the appropriate chain-of-custody documentation. All boreholes will be fully sealed with hydrated bentonite, or impermeable material that is acceptable to the permitting authority, after completion.The surface completion will match the surrounding material (e.g., concrete, asphalt). 3.2.5.5 Indoor and Ambient Air Sampling Protocols for collecting indoor air samples from structures that have indicated the potential for a vapor intrusion pathway to be completed are described below. Indoor air sampling, if performed to evaluate vapor intrusion from subsurface contaminants,will be performed in accordance with Programmatic QAPP. Indoor and Ambient Air Sample Collection Indoor air sampling, if performed to evaluate vapor intrusion from subsurface contaminants,will be performed in accordance with Programmatic QAPP. For CVCI-D&E-specific projects, passive indoor air samplers are Prepared for: Department of Toxic Substances Control AECOM 14