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Record of Decision System (RODS)
COMMENCEMENT BAY, NEAR SHORE/TIDE FLATS
Abstract
| Site Name: | COMMENCEMENT BAY, NEAR SHORE/TIDE FLATS |
| Address: | ADJ TO RUSTON WAY & TIDEFLATS IND. AREA |
| City & State: | PIERCE COUNTY WA 98421 |
| County: | PIERCE |
| EPA ID: | WAD980726368 |
| EPA Region: | 10 |
| NPL Status: | Currently on the Final NPL |
| ROD Type: | Record of Decision |
| ROD ID: | EPA/ROD/R10-93/062 |
| ROD Date: | 06/16/1993 |
| Operable Unit(s): | 22 |
| Media: | Soil, debris |
| Contaminant: | Metals |
| Abstract: | The 67-acre Commencement Bay-Nearshore/Tidefats site, a former lead and copper smelting facility, is part of the larger 950-acre property located in Ruston and Tacoma, Washington. Land use in the area is residential, including schools, playgrounds, and parks. The site also contains the Asarco smelter, inactive since 1985, approximately 4,000 residents, and part of a coastal zone. In 1890 lead smelting operations begam, but in 1912, Asarco converted the plant to a copper smelter. The smelting process specialized in processing ores with high arsenic concentrations and also recovered arsenic-trioxide and metallic arsenic as by-products. As part of the processing of copper from ores and concentrates, slag, a hard, glassy material containing elevated concentrations of arsenic, lead, and other metals, was produced. Smelter slag was used around the community for driveways, walkways, curbs, parking areas, and as backfill in utility trenches. In 1985, copper smelting operations ceased, and the arsenic production plant closed in 1986. As a direct result of 95 years of airborne emissions from smelting operations, historical studies throughout the 1970s and 1980s identified elevated contaminant concentrations in multiple environmental media, including soil, house dusts, indoor and outdoor air, and garden vegetables. Once copper smelting and arsenic processing ceased, ambient air concentrations of these metals were reduced by more than 90 percent. In 1985 and 1988, State investigations indicated that ingestion of contaminated soil was the primary route of exposure to arsenic. In 1989, EPA required Asarco to remove contaminated soil to a depth of three inches at the 11 nonresidential high-use properties, and to replace the excavated soil with 9-12 inches of imported soil. EPA has divided the Commencement Bay - Nearshore/Tideflats site into seven OUs for remediation; four of which are associated with the Asarco Smelter. Three previous 1998, 1989, and 1990 RODs addressed source and ground water contamination at the site as OUs 3, 1and 5, and 7, respectively. This ROD addresses the arsenic- and lead- contaminated soil and slag in the area surrounding the smelter, known as the Ruston/North Tacoma Study Area, as OU4. Future RODs will address the contaminated soil, sediment, ground water, and surface water at the site, as OUs 2, 6, and 7. The primary contaminants of concern affecting the soil, and slag/debris are metals, including arsenic and lead. SELECTED REMEDIAL ACTION: The selected remedial action for this site includes sampling individual properties to determine if soil exceeds the established EPA action levels of 230 mg/kg for arsenic and 500 mg/kg for lead, followed by excavation of any contaminated soil and slag to a depth of 18 inches;replacing theexcavated soil and slag with clean soil and gravel and re- landscaping; capping contaminated dirt alleys and parking areas with asphalt to provide an impermeable barrier to contaminants, or removing the soil and replacing it with gravel; disposing of the contaminated soil offsite; implementing a maintenance and monitoring program for the capped areas; placing a marker to clearly identify the base of the cap; fencing and planting lowlying shrubs in steeps contaminated areas where excavation is not possible; establishing a temporary staging area or transfer facility for excavated soil, if necessary; implementing safety measures, including air monitoring; developing a soil testing, collection, and disposal program to remove soil from residences; and developing and implementing institutional controls. The estimated present worth cost for this remedial action ranges from $60,000,000 to $80,000,000, which includes an O&M cost of $2,000,000 for 7 years. PERFORMANCE STANDARDS OR GOALS: Soil cleanup goals are based on reduction of the additional potential skin cancer risk of arsenic to no more than 5 in 10,000; a national goal of reducing lead levels in children's blood to no greater than 10 ug/dl; and EPA guidance for soil lead cleanup levels, including arsenic 230 mg/kg and lead 500 mg/kg. INSTITUTIONAL CONTROLS: Institutional controls will be implemented in the form of community protection measures to prevent or limit public exposure to soil contamination by establishing a community relations program, providing a means for notifying potential future property owners if contaminated soil remains at the property, controlling activities that intentionally disturb contaminated soil, providing guidelines or permit requirements for conducting those activities with the minimum amount of contact with or movement of the soil, ensuring the long-term integrity of the caps, and establishing a post-cleanup storage/disposal program for contaminated soil. |
| Remedy: |
The EPA has divided the Commencement Bay/Nearshore Tideflats Superfund site into seven operable units (OU's) in order to facilitate the investigation, analysis, and cleanup of this very large site. Four of these OU's are associated with the Asarco smelter: * OU 02 Asarco Tacoma Smelter * OU 04 Asarco Off-Property (Ruston/North Tacoma Study Area) * OU 06 Asarco Sediments * OU 07 Asarco Demolition The remedy described in this ROD addresses OU 04 and involves the cleanup of arsenic and lead contaminated soils and slag in the Study Area, the residential community surrounding the smelter. This remedy will address the principal threat posed by conditions at the site, which is the ingestion of contaminated soil and dust, and includes: * Designation of "action levels" or concentrations of arsenic or lead in soil. Engineering measures will address properties or areas that exceed action levels. * Sampling of individual properties to determine if soil exceeds the action levels. * Excavation and off-site disposal of contaminated soil and slag from properties that exceed action levels. Contaminated soil below 18 inches will not be excavated but will be capped. * Excavation of slag from all other properties. * Replacement of excavated soil and slag with clean soil and gravel. * Asphalt capping or soil removal and replacement with gravel of contaminated dirt alleys and parking areas. * Fencing and planting low lying shrubs in steep areas. * Soil collection program for soil above action levels that is not excavated during the cleanup (e.g., soil below 18 inches that is uncovered in the future). * The development and implementation of community protection measures (CPMs). CPMs are administrative requirements that will address soil that is not excavated but that contains concentrations of arsenic or lead that exceed either action levels or levels commonly found in urban areas. Statutory Determinations The selected remedy is protective of human health and the environment, complies with Federal and State requirements that are legally applicable or relevant and appropriate to the remedial action, and is costeffective. This remedy utilizes permanent solutions and alternative treatment technologies, to the maximum extent practicable for this site. However, because treatment of the principal threats of the site was not found to be practicable, this remedy does not satisfy the statutory preference for treatment as a principal element. Because the remedy may result in hazardous substances remaining onsite above health-based levels, a review will be conducted no less often than every five years after commencement of remedial action to ensure that the remedy continues to provide adequate protection of human health and the environment. Gerald A. Emison Acting Regional Administrator U.S. EPA Region 10 6-16-93 Date |
| Text: |
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