Closure Plan Approval and Closure Certification Acknowledgement for Southern California Edison Long Beach Generating Station

Closure Plan Approval and Closure Certification Acknowledgement for Southern California Edison Long Beach Generating Station

An Investigation performed at the surface impoundment including the associated piping detected elevated concentrations of heavy metals in the soil and VOCs in the ground water. The concentration of metals in the underlying soil was elevated above the ambient levels at the site (the site was built on materials dredged from adjacent channels in the early 1900's and does not have true background soils). The groundwater investigation detected VOCs during the first three years of quarterly sampling but VOCs were not detected after 1999. The concentration of metals detected in ground water was not elevated above the levels detected in the upgradient groundwater monitoring wells. The CDR closure plan activities performed by SCE included the following: - Removal and off-site transport of 25 cubic yards of contaminated soil; - Backfill and compaction of excavated areas with materials obtained from off-site sources; - Waste characterization of excavated materials; - Sampling of soil and ground water to verify that the residual contamination did not exceed the closure performance standard; - Leachate liner test and leachate risk assessment of the surface impoundment liner; - Health-Based Risk Assessment; - Ecological Screening Assessment. The removal action occurred because elevated levels of metal were detected in an area with dimensions of 20 feet in length, 25 feet in width, and 2.5 feet in depth in the northwest portion of the project area. This area was considered a "hot spot" or an isolated area where elevated levels of contaminants were detected. The "hot spot" was removed by excavation, confirmation samples analyzed, and the area backfilled with a cement slurry mix. Approximately 25 cubic yards of soil was removed and transported off site to an appropriate disposal facility. The cement slurry mix received from a commercial supplier consisted of portland cement and pozzolan. A health-based risk assessment (HBRA) was conducted. Because the site is zoned industrial and is continuing and is continuing to operate as a generating station, an industrial worker and construction worker scenario was assessed, rather than a residential scenario. The HBRA considered (1) soil, ingestion and dermal contact were the two exposure pathways considered to be complete; (2) air, inhalation of airborne dust and vapors was considered a complete pathway for future industrial and construction workers (inhalation was not considered to be complete for current workers because the soil beneath the surface impoundment area are covered); (3) ground water, no exposure pathways are complete because no consitituents of concern (COCs) were identified for ground water; and (4) surface water, the exposure pathways are incomplete because no surface water bodies are located on the site; the Back Channel is not used for recreation or construction, therefore, it does not have any human receptors. The HBRA risk assessment determined that the residual contamination in soil and dust and vapors in do not pose a risk to human health and the environment for an industrial/construction worker scenario, or ecological receptors at the site. The exposure pathways for human health and the environment and ecological receptors are incomplete or are complete but do not pose a risk, or have been mitigated. An ecological screening evaluation found no risks to potentially affected habitats for plants or terrestrial receptors in the surface impoundment and the Back Channel. The site offers poor habitat for special status or sensitive terrestrial wildlife. The generating station is paved with minimal vegetation of non-native plants. No plants are identified as receptors of ecological concern and no terrestrial receptors of concern are identified at the surface impoundment. The Back Channel may be a foraging area for the California Brown Pelican; however, the exposure pathway is incomplete due to the lack of COCs as a result of dilution. Aquatic receptors, fish and estuarine invertebrates in the Back Channel were identified as potential receptors of ecological, commercial or recreational concern. The exposure pathways for air, dust and soil at the surface impoundment are incomplete for the aquatic receptors, because of the absence of VOCs in subsurface soil. While the ecological exposure pathway for groundwater was evaluated as complete, exposure point concentrations (EPCs) did not exceed the water quality criteria when compared to water quality criteria protective of saltwater and freshwater life. The land use will be restricted to industrial use by a Land Use Covenant (LUC) recorded on the deed of the property. An Implementation and Enforcement Plan (IEP) included as an appendix to the CDR ensures compliance with conditions of the LUC. The LUC and EIP require: (1) written notification to perspective purchasers of a release of hazardous substances at the property; (2) require notification to contractors performing work who will be in contact with the subsurface soil of the presence of hazardous substances; and (3) annual inspections to ensure compliance with the requirements of the LUC.

Long Beach

Los Angeles