Americana Motel Property Removal Action Workplan

Americana Motel Property Removal Action Workplan

The Department of Toxic Substances (DTSC) approved the Americana Motel Property (Project Site) Removal Action Workplan (RAW) to address the impacts of the chemicals benzene, bromodichloromethane, chloroform, dibromochloromethane, ethylbenzene, naphthalene, tetrachloroethene (PCE), trichloroethene (TCE), total petroleum hydrocarbons as gasoline (TPH-g), toluene, and/or xylenes in soil vapor, and dieldrin and arsenic in the soil at the Project Site. The cleanup decision document, referred to as a RAW, specified the removal action objectives, identified the contaminants of concerns (COCs), and evaluated alternative remediation proposed for the Project Site. The approved remediation activities consist of Excavation and Off-Site Disposal of the contaminated soils and the installation of a Vapor Intrusion Mitigation System (VIMS). The VIMS is fundamentally incorporated into the physical design and will be installed as part of the construction process for the proposed residential development. The removal action will consist of the following components: • Excavation of approximately 4,130 cubic yards of arsenic impacted soil and 725 cubic yards of dieldrin impacted soil. • Approximately 4,855 cubic yards of clean fill will be imported to the Project Site. The VIMS will have the following major components according to the RAW: • A sub-slab vapor barrier including the following components from bottom to top: o Base membrane to limit damage to the overlying geomembrane by providing high impact strength. o Either a spray-applied geomembrane or single sheet membrane located beneath all slabs and footings to prevent vapor intrusion. o Protection geotextile to provide protection to the vapor barrier from potential punctures that could occur during construction of the building foundation and slab. • A passive ventilation system that generally includes a perforated Schedule 40 polyvinyl chloride (PVC) vent piping network embedded in sand and located beneath the sub-slab vapor barrier. The vapors captured in the perforated PVC are directed into vent risers that terminate above the roofline of the structures. • Utility and/or conduit seals for conduits that penetrate the slab foundation to reduce the potential for the migration of volatile organic compounds (VOCs) into indoor air. • Subsurface trench cut off for utilities that extend beneath the slab in order to prevent VOCs from migrating through permeable trench backfill into the structure. • An optional active ventilation system may be implemented via the installation of mechanical blowers if deemed necessary.

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