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Cleanup in Vulnerable Communities'Initiative Discovery Project Reference:Favorite Cleaners and Enforcement Discovery Investigation Work Plan Project Number:60688620 • Temporary well screens should be approximately 6 to 48 inches in length. Screens measuring 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 volatile organic analysis(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)and existing grade. 3.2.5.5 Indoor and Outdoor 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 the Programmatic QAPP. Indoor and Outdoor Ambient Air Sample Collection Indoor air sampling, if performed to evaluate vapor intrusion from subsurface contaminants,will be performed in accordance with the Programmatic QAPP. For CVCI D&E Discovery Investigation-specific projects, passive indoor air samplers are recommended over the use of Summa®canisters for the collection of indoor air data. However, passive or canister sampling may be used as long as the sampling protocols are in accordance with the Programmatic QAPP. The Discovery Investigation will utilize active indoor air sampling using Summa®canisters per the Programmatic QAPP.Afield indoor air survey will be conducted prior to the indoor air sampling to characterize any chemicals or items that may impact the indoor air samples.Additionally, to evaluate potential preferential entry points for soil vapor, the building will be field-screened with a field PID capable of reading VOCs in the low parts per billion by volume range. Indoor air samples will be collected concurrently with sub-slab vapor samples. Sub-slab vapor samples will be collected shortly after indoor air samples to provide indoor air/sub-slab vapor data.This protocol will minimize the potential for VOCs to be released to indoor air during sub-slab vapor sampling. Active indoor air samples will be collected in evacuated, individually certified clean, stainless-steel Summa®canisters per the DTSC Final Draft Supplemental Vapor Intrusion Guidance(DTSC, Cal EPA, SWRCB 2023).The samples will be submitted to Eurofins Air Toxics, Inc. in Folsom, California, an accredited analytical laboratory,for USEPA Method TO-15 SIM analysis.When collecting indoor air samples for the evaluation of potential impact of contaminant releases,the following should be considered: • Indoor air samples should be collected over a 24-hour period for residential structures, over an 8-hour period for nonresidential structures, and over a typical school day for students.After vapor intrusion is confirmed, additional sampling events should be conducted to produce representative concentrations of the monitored compounds over the anticipated daily exposure period for building occupants. • Floors, including the basement, of a residential structure potentially subject to vapor intrusion should be sampled for indoor air quality. Based on site-specific conditions, it may be necessary to sample additional units of an apartment building. Sampling devices should be located in the breathing zone, approximately 3 to 5 feet off of the ground for adults and at lower sampling heights if the receptors of concern are children as in a daycare center or school. Samples should be collected in the center of the room, away from doors.At a minimum, it is recommended that sampling points include the primary living area and likely locations for subsurface vapor entry(typically the bathroom or kitchen). • When sampling commercial or industrial buildings,the number and locations of samples should be based on site-specific conditions. Samples should be collected from primary work areas and near the points of vapor entry to help define the potential routes of entry such as sumps, elevator shafts, or floor drains. For the initial indoor Prepared for: California Department of Toxic Substances Control AECOM 17