LA CADA Facility Removal Action Work Plan

The project consists of implementing the Soil Removal Action Work Plan (RAW) to address arsenic on approximately 1 acre of land located at 10425 South Painter Avenue, Santa Fe Springs (Site), also known as the “Allen House”. The project activities include removing the existing asphalt pavement and installing new asphalt; excavating approximately 460 cubic yards (CY) of soil, disposing of the soil off-site, and backfilling with clean imported soil in landscaped areas. In addition, institutional controls, including a land use covenant, will be implemented to manage residual arsenic-impacted soil. The project is estimated to take approximately 5 to 9 days and require up to 88 truck trips. Background: The Site contains a single-story in-patient rehabilitation facility (11,042-square feet), parking lot, and playground on a parcel identified by Los Angeles County assessor parcel number (APN) 8011-014-024. The property is bordered by Painter Avenue to the east. The surrounding properties are commercial, retail, and light industrial businesses. On March 10, 2020, DTSC entered a Standard Voluntary Agreement, Docket No. HAS-FY19/20-097, with LA CADA to investigate and remediate the Site. The Site building was constructed in 1965 with remodeling and additions completed in 1967. Prior to construction of the Site building, oil wells may have been present on the parcel during the 1950s and 1960s. The Site may have also been used to store chemicals associated with a spray chemical manufacturer between approximately 1953 and 1961. Standard Oil (Chevron) likely occupied the Site or portions of it between 1963 to 1972. Standard Oil’s operations at the Site included the installation of a 12,000-gallon gasoline underground storage tank (UST) in 1976. The UST was located in the northwestern corner of the Site and used in the 1970s to fuel company trucks. The UST was removed in the late 1980s; no total petroleum hydrocarbons or benzene, toluene, ethylbenzene, or xylene (BTEX) compounds were detected in soil samples collected during UST removal. McFarland Energy occupied the Site from 1972 to 1998 and used it for administrative offices. The Site was purchased by LA CADA in 1998 and has been operated as an in-patient substance abuse treatment facility. The Site has undergone recent renovations and is currently occupied. Future possible occupants of the facility include women with children. Previous Investigations: Several rounds of Site assessments have been completed. Arsenic was identified in soil at concentrations (maximum of 650 milligrams per kilogram) exceeding the residential screening levels and/or the Southern California regional background. In addition, low concentrations of volatile organic compounds (VOCs) were identified in soil vapor. Two rounds of sub-slab vapor and indoor air sampling were conducted at the Site in October 2024 and May 2025. Results of the 2024 and 2025 sub-slab vapor and indoor air sampling and human health risk evaluation indicate that vapor intrusion risk is below the DTSC risk management range for the current Site building and residential scenarios. As such, potential exposures to VOCs are not evaluated in this soil RAW. Project Activities: Include soil excavation (typically to 18 inches below ground surface) using mini excavators and/or hand tools. The excavated soil will be moved to designated soil stockpile areas. Hand excavation will be conducted close to existing building, utilities, and mature trees. The bottom of the excavation will be covered with a bright orange demarcation fabric that will provide immediate visual evidence that impacted soil has been encountered during any future subsurface work in this area of the Site. The excavated area will be backfilled with imported clean soil. There will be a Soil Management Plan (SMP) that will address excavation requirements, including South Coast Air Quality Management District (SCAQMD) Rule 403 site preparation (e.g., signs, fencing, windscreens, etc.), notifications, and recordkeeping/reporting and SCAQMD Rule 1466 requirements. Perimeter air monitoring will be conducted by an environmental contractor to evaluate whether standard dust control procedures (e.g., soil wetting) are adequate, or engineering controls are required to mitigate potential exposures to arsenic in dust that may be emitted to ambient air during earthwork activities. Based on perimeter air monitoring results, the contractor will require to implement additional dust suppression efforts. Because residual arsenic in soil will not meet unrestricted land use criteria, restriction on land development and use is required. A Land use covenant will be placed on the property deed and recorded with the Los Angeles County Assessor’s office. The land use covenant shall specify that the areas (defined by legal description and exhibit) with arsenic in soil that exceeds the regional background concentration require additional investigation or remedy prior to redevelopment. Although not anticipated, in the event biological, cultural or historical resources are discovered in the course of project activities, work will be suspended while a qualified biologist, cultural or historical specialist makes an assessment of the area and arrangements are made to protect or preserve any resources that are discovered. If human remains are discovered, no further disturbance will occur in the location where the remains are found, and the County Coroner will be notified pursuant to the Health and Safety Code, Chapter 2, Section 7050.5.