Record of Decision System (RODS)
COMMENCEMENT BAY, NEAR SHORE/TIDE FLATS
|Site Name:||COMMENCEMENT BAY, NEAR SHORE/TIDE FLATS|
|Address:||ADJ TO RUSTON WAY & TIDEFLATS IND. AREA|
|City & State:||PIERCE COUNTY WA 98421|
|NPL Status:||Currently on the Final NPL|
|ROD Type:||Record of Decision|
Site had heavy industry such as aluminum processing, chemical, pulp and paper, and primary smelting contamination of waterways and land areas of the tide flats. Was originally part of one site called Commencement Bay, which is now 2 sites. The Commencement Bay Nearshore/Tideflats Superfund site is located on the western shore of Commencement Bay in Tacoma/Ruston, Washington. It consists of 67 acres of property owned by Asarco Inc., and a 23-acre slag peninsula. The site began operation as a lead smelter in 1890. During the active industrial life of the smelter, the primary product was refined copper. By products of the copper smelting process included sulfur dioxide, arsenic trioxide, arsenic metal, and copper reverbatory slag. Copper smelting operations were discontinued in 1985, and the facility was taken completely out of production in 1986. Land use in the vicinity of the site is recreational and light residential.
The general area of the former Asarco Smelter consists of steep slopes extending down to Commencement Bay producing bluffs along portions of the shoreline. The adjacent slag peninsula is composed of different forms of slag (molten or granulated) that were poured or placed on many occasions between 1930 and 1970. The Tacoma Yacht Club building, a paved access road, and paved parking areas are located on the slag peninsula. An estimated 15 million tons of slag exist at the smelter property and slag peninsula.
Surface water features at the site include surface water in the cooling pond and south and east stack hill areas and a number of springs and seeps around the stack hill and arsenic kitchen areas. Surface water drains into one of four drain systems and then into outfalls at the site.
A complex pattern of groundwater flows through or beneath the smelter property, including through the slag into Commencement Bay. Three primary groundwater aquifers have been identified; two shallow aquifers and one deep aquifer. Because of the high degree of fractures in and porous nature of the slag, the tides bring seawater inland several hundred feet where it mixes with groundwater. The groundwater within each of the three aquifers is designated as either potential drinking water (Class IIB) or as non-potable water (Class III). Groundwater at or near the site is not being used as a drinking water source. Several small areas of the site have been identified as potential wetlands and if these areas are confirmed as wetlands and if remediation occurs in these areas, the extent of mitigation will be determined during remedial design.
Operable Unit 2 (OU 2) addresses the final cleanup remedy for soil, slag and surface water and disposal of hazardous soils, demolition debris, and residential soils. OU 2 is intended to be an interim action for groundwater.
OU 4 addressed arsenic and lead contaminated soils in residential yards and in public right of ways surrounding the former smelter facility. The Record of Decision (ROD) addressing this OU required excavation or capping of contaminated residential soil and by 1994, 75 private properties had been cleaned up and 269 yards had been sampled.
Operable Unit 6 addresses the Asarco sediments and groundwater. The former Asarco copper and lead smelter facility (the "Facility") is located within the municipal boundaries of Ruston and Tacoma, Washington. The site is located on the northeast side of the Point Defiance Peninsula and borders Commencement Bay. The general area consists of steep slopes extending down to Commencement Bay producing bluffs along portions of the shoreline.
The onshore portion of the Facility is approximately 67 acres in size. In addition, approximately 30 acres of offshore intertidal and subtidal lands are under Asarco ownership. The State also owns a portion of the offshore lands within OU 06. State-owned aquatic lands are managed by the Washington State department of Natural Resources.
The selected remedy for groundwater is Alternative GW-B. Alternative GW-B includes elements currently being implemented under the Operable Unit (OU) 02 Record of Decision (ROD) (EPA, March 1995) plus long-term monitoring and institutional control requirements addressed in this ROD. Together, these remedy elements comprise EPA's Selected Remedy for the Sediments/Groundwater Operable Unit. This remedy is being selected because evaluations conducted by the Asarco Sediment/Groundwater Task Force indicate that marine sediments and the waters of Commencement Bay will be protected by the remedial actions being implemented under the OU-02 cleanup. Combined with long-term monitoring and institutional controls being added by this ROD, the groundwater is expected to be permanent and to meet the Remedial Action Objectives.
The OU 02 remedy is in progress with substantial completion scheduled for 2003 and final completion expected in 2005. The OU-02 remedy elements applicable to groundwater and included in Alternative GW-B are source excavation and placement in the On-site Containment Facility, site capping and surface water controls, groundwater interception/treatment, and removal of leaking underground piping. Source control measures will reduce the volume of contaminants that are transferred to the groundwater. Capping, surface water controls, groundwater interception, and removal of leaking pipes is expected to reduce groundwater discharge to Commencement Bay by approximately 75 to 95 percent.
The selected remedy includes restrictions on groundwater use for domestic or industrial purposes. The objective of the prohibition is to prevent human exposure to contaminated groundwater. This will be achieved by prohibiting the drilling of water wells (other than for environmental monitoring or treatment) and prohibiting the use of groundwater as a drinking water source. Specifically, no water wells will be permitted in the shallow and deep aquifer systems. The prohibition on groundwater use is expected to be in force into perpetuity for shallow groundwater (slag, marine wand, and intermediate aquifers) because source materials (e.g., slag) will remain in place and in contact with shallow groundwater, under the terms of the OU-02 ROD. Therefore, these source materials will continue to be in direct contact with groundwater. This ROD will also implement a prohibition on use of deep aquifer groundwater until such time groundwater quality complies with applicable health-based criteria (e.g., Maximum Contaminant Levels). Prohibitions on groundwater use would only be rescinded or relaxed if groundwater contaminants no longer exceed acceptable levels as determined by EPA. The prohibition on groundwater use may be implemented through a combination of governmental controls (e.g., zoning restrictions or ordinances) and enforceable use restrictions that run with the land (e.g., a servitude or an easement that includes use restrictions and is properly recorded).
Long-term groundwater monitoring will occur on a regular basis after the remedial actions is complete. The objective of the monitoring program will be to assess the performance of the Selected Remedy over time and to verify that the remedy continues to be protective of human health and the environment. At a minimum, monitoring wells at the downgradient perimeter of the site (along the Commencement Bay and Yacht Basin shorelines) will be monitored. Monitoring wells upgradient of the site and near key source areas (or former source areas) will also be required. Monitoring nearshore surface water in Commencement Bay will be required to assess impacts that discharging groundwater may have on the bay water.
At a minimum, post-remedial action groundwater monitoring will include measurement of the static groundwater level, the general water quality parameters, metals, and organics.
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