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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 3. Sampling and Analysis Plan A sampling and analysis program will be conducted to evaluate the potential presence of chemical constituents in subsurface soil vapor, indoor and ambient air, and groundwater if encountered.The Discovery Investigation will consist of a soil gas survey including active sub-slab vapor sampling as well as indoor and ambient air sampling, and groundwater sampling if encountered during the subsurface soil vapor sampling.The DI will be designed to assess environmental conditions at suspect areas identified during the preparation of this Work Plan. The USEPA-approved methods will be used for sampling and analysis,wherever possible. Figures 4A and 4B show the proposed sampling locations. Figure 5 presents the preliminary conceptual site model (CSM).All field work will be done in accordance with the Site-specific addendum to the Programmatic HASP presented in Appendix A. The following sections describe the recognized environmental concerns, sampling strategy, rationale, investigative methods and procedures,sample analysis program,sample handling, decontamination procedures, and management of investigation-derived waste (IDW). 3.1 Recognized Environmental Concerns The following potential sources of hazardous materials contamination have been identified at the Site: • Bobson Cleaners Inc.—Dry-cleaning operations from at least 1969 to 2005 may have resulted in the release of chlorinated solvents. • Former Manteca Equipment Rental—This business operated onsite.The facility had a LUST case opened with CRWQCB in 1991. Remediation was completed onsite in 1997, and the case was closed in 1999. • Manteca Ford—This facility is south and upgradient of the Site.This facility reportedly has two inactive 1,000- gallon LISTS for waste oil and gasoline, plus an AST of unknown contents or capacity. • Delta National Bank—This facility is west and cross-gradient of the Site.This facility reportedly has one or two inactive LISTS of waste oil and/or petroleum. • Manteca Tire—This facility is west and cross-gradient of the Site.This facility is listed as a chemical storage facility and has had several violations from the local regulatory agency for its hazardous materials business plan (HMBP)and emergency response plans. Reportedly,two 200-gallon ASTs containing oil and waste oil each plus two 55-gallon drums containing new and waste antifreeze each were discovered onsite and not entered into the HMBP inventory, resulting in a violation in 2015. 3.2 Sampling Strategy, Rationale, and Approach All engineering or geologic work, performed as a portion of the DI,will be performed or supervised by a registered PE and/or PG in compliance with the requirements of the Professional Engineers Act, Business and Professions Code Sections 6700-6899 and 7838,and the Geologist and Geophysicists Act, Business and Professions Code Sections 7800-7887. The field discovery investigation will consist of the collection of soil gas,sub-slab soil gas, indoor air, and ambient air, samples to assess environmental conditions at the Site. If site conditions warrant the collection of groundwater samples,the sampling will be conducted concurrently with the soil gas survey. Subcontractors will be selected for conducting the soil gas survey and for collecting groundwater samples as specified in this Work Plan.AECOM will be responsible for utility clearance and obtaining any required agency permits prior to initiating the subsurface investigation. Soil gas and groundwater samples will be analyzed by Eurofins Air Toxics Laboratory, a State-certified laboratory in Folsom, California. 3.2.1 Soil Gas and Sub-Slab Soil Gas The purpose of the soil gas survey is to assess potential presence of volatile organic compounds(VOCs)in the subsurface.The soil gas survey will be conducted in accordance with the Programmatic QAPP that was developed in accordance with current DTSC Advisory-Active Soil Gas Investigations (DTSC 2015). Prepared for: Department of Toxic Substances Control AECOM 10