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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 4. Quality Assurance Project Plan This section describes the QAPP,which provides an appropriate level of QA and QC regarding the reliability and usability of the data generated during the DI.An integral part of the QAPP is proper field sampling and documentation procedures,which have already been described in Section 3 above and,thus,will not be repeated herein.This section sets forth the policies, procedures, and activities for the identification and documentation of the quality of the data generated during the performance of the DI. During the DI, a variety of data will be collected. Each sample collected may be analyzed for a number of different chemicals, depending on the rationale for sample collection. However, not all chemicals detected will necessarily be attributable to an onsite release, and not all of the data will necessarily be of acceptable quality. Data collected will be evaluated to determine which of the chemicals identified are likely to be Site-related and to assess whether the reported concentrations for these chemicals are of acceptable quality for use in the human health screening evaluation. 4.1 Data Quality Objective Process The project DQOs developed specifically for the planned sampling and analysis program have been determined based on USEPA's seven-step DQO process (USEPA 2000). The Project QA Manager will evaluate the project DQOs to determine whether the quantitative and qualitative needs of the sampling and analysis program have been met. The project definition associated with each step of the DQO process can be summarized as follows: • State the problem: The purpose of the sampling program is to determine whether the proposed Site is acceptable for an intended use scenario: The Site was developed in 1968 and operated as a dry cleaner from at least 1968 to 2005,according to city directories and the EDR reports.A total of 127 manifests for PCE waste was identified on the HWTS database from 1993 until 2005.A 30-gallon PCE release occurred due to power failure,which was reported to the San Joaquin County Emergency Services on May 2, 2001.Additionally, the boiler overflowed, and evacuation of the building was required.The historical dry cleaner operations utilizing PCE with a reported spill is considered a REC, and the release of chlorinated solvents may pose a risk to human health and the environment. Currently, the Site is operating as a commercial space and has been occupied by an insurance office and a massage parlor since 2010.The Site case is listed as open with vapor intrusion verification monitoring needed. Discovery sampling is necessary to determine if the former dry-cleaning facility released chlorinated solvents to the environment. • Identify the Decision:The data obtained from the sampling and testing activities will be used to evaluate whether releases of hazardous substances from historical uses have occurred at the Site.The data obtained will be further evaluated to determine to what extent any found contamination or naturally occurring constituent concentration will result in risk of exposure.The data results will be compiled and used to assess the relative threat associated with onsite constituent concentrations through screening risk evaluations performed in accordance with the procedures set forth in the Programmatic QAPP. Based on the screening risk calculations for the Site,the suitability of the property for its intended development will be determined. • Identify Inputs to the Decision: The investigation report will contain general descriptions of inputs to the decision. Inputs to the decision will include results of analytical testing of soil gas samples and/or groundwater samples from selected locations on the Site. Each matrix that is tested will be tested for the specified analytes discussed in Section 3, and the results will be presented in investigation report.An example table and figure are included as Table 4 and Figures 6A and 6B in this work plan. • Define the Study Boundaries: The boundaries of the field sampling and analysis program will be the perimeter of the Site as defined by the Phase I Report conducted by AECOM (AECOM 2023)and per site access.The depth will be limited to 16 feet bgs. Soil gas will not be conducted during inclement weather or for 5 days following a rain event with greater than 0.5 inches of precipitation during a 24-hour period. Sampling will only occur Monday through Friday between 7am and 6pm. • Develop a Decision Rule: Decisions will be based upon laboratory results for the target constituents and presented in figures and tables similar to the templates in Figure 6 and Table 4,for each respective matrix Prepared for: Department of Toxic Substances Control AECOM 23