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Record of Decision System (RODS)



City & State:  MARYSVILLE  WA  98270
EPA ID:  WAD980639256
EPA Region:  10
NPL Status:  Deleted from the Final NPL
ROD Type:  Record of Decision
ROD ID:  EPA/541/R-98/063
ROD Date:  09/29/1998
Operable Unit(s):  01
Media:  Groundwater, Leachate, Other, Sediment, Soil, Surface Water
Contaminant:  Base Neutral Acids, Dioxins/Dibenzofurans, Inorganics, Metals, PAH, PCBs, Pesticides, VOC
Abstract:  Please note that the text in this document summarizes the Record of Decision for the purposes of facilitating searching and retrieving key text on the ROD. It is not the officially approved abstract drafted by the EPA Regional offices. Once EPA Headquarters receives the official abstract, this text will be replaced.

The Tulalip Landfill occupies approximately 147 acres and is located on a low-lying island (commonly referred to as North Ebey Island) in the Snohomish River delta. This island is within the floodplain of the Snohomish River. Located within the bounds of the Tulalip Indian Reservation, the landfill lies generally between Marysville and Everett, Washington.

Prior to landfilling activities, the land on which the landfill is located consisted of relatively undisturbed intertidal wetlands, and reached heights of about 3 to 6 feet above mean sea level (MSL). Today, the landfill reaches heights of about 12 to 20 feet above MSL. The landfill is bounded by a perimeter berm that is approximately 15 feet high. During landfilling operations, barge canals were cut into the island to allow water barges bearing refuse to transport waste into the landfill. Initially, waste was removed from the barges and placed directly on top of adjacent wetlands. During later operations, wetlands adjacent to the canals were dredged prior to placing the waste into dredged areas. In general, these barge canals were deeper than other parts of the landfill and are now filled with waste. The average depth of fill throughout most of the landfill is about 17 feet; in the old barge canals the fill depth reaches about 30 feet. Three to four million tons of mixed commercial and industrial waste were deposited in the landfill during its period of operation from 1964 to 1979. The waste is covered with silt, silty sand, clay, and medium sand, and demolition and construction debris at depths of up to 11 feet.
The results of the Remedial Investigation (RI) indicate that there is a mound of contaminated groundwater (landfill leachate) within the landfill waste. This leachate mound is fed by precipitation, and its height varies between approximately 10-16 feet above MSL. Because the mound is considerably higher than the mean sea level and the ground water level surrounding the landfill, the weight of this leachate mound drives landfill contaminants out and away from the landfill. Some of the leachate (approximately 5-35%) is pushed out of the outer edge of the perimeter berm and flows onto wetlands and into tidal channels surrounding the landfill. Most of the leachate seeps occur outside of the landfill berm, but one seep that was sampled during the RI (SP-01) originates on the landfill surface. The remainder of the leachate (approximately 65-95%) is driven downward by the weight of the leachate mound into ground water beneath the landfill, where it migrates outward and is discharged to waterways surrounding the landfill.

Groundwater beneath the site is brackish and therefore unusable as a potable water source. Site studies indicate that contaminated groundwater from the landfill migrates to the wetlands and sloughs surrounding the site and does not pose a threat to ground water drinking water sources located across the sloughs. The areas surrounding the landfill have significant aesthetic, environmental, economic, and recreational value. The landfill is located within the Puget Sound Estuary, one of 28 estuaries in the country that have been targeted for protection and restoration under the National Estuary Program. The State of Washington has classified the surface waters surrounding the site as 'Class A' waters of the State, which are characterized as generally 'excellent' waters, where water quality meets or exceeds the requirements for all, or substantially all, designated uses. The tidal mudflats and marsh habitats surrounding the landfill are natural resources that provide spawning and foraging areas for wildlife species. The Snohomish River delta is designated as a Washington Shoreline of Statewide Significance by the Washington State Department of Ecology, and designated as an Area of Major Biological Significance (AMBS) for American shad and English sole by the U.S. Fish and Wildlife Service.
The landfill is surrounded on all sides by environmentally sensitive wetlands, including an area of approximately 160 acres of salt marsh and mudflats located immediately west of the landfill. Because of ongoing environmental problems associated with the landfill operations, the landfill was closed in 1979. In April 1995, with the support of the Governor of the State of Washington, the Environmental Protection Agency (EPA) published the final rule adding the site to the National Priorities List (NPL). In August 1993, EPA signed an Administrative Order on Consent with several Potentially Responsible Parties to conduct a RI and Feasibility Study. In March 1996, EPA published the Record of Decision (ROD) for the Tulalip Landfill interim remedial action. A ROD was issued in September 1998.
Remedy:  The final on-source remedy is the interim remedy documented in the March 1996 Record of Decision (ROD). With the finalization of this remedy, no further remedial action is necessary for the on-source area. The selected remedy for the off-source area (wetlands) is institutional controls. This selection assumes the completion of the on-source remedy. Institutional controls would protect human health by warning of the potential dangers associated with the eating of fish and shellfish from the affected area. In addition, the potential for this type of exposure is relatively low given the site setting and access difficulties. Natural attenuation of contamination in the tidal channel sediment would protect the marine receptors. This alternative consists of maintaining existing signs, and as necessary, posting new signs along the perimeter of the sloughs and landfill warning of the potential risk from harvesting and eating fish and shellfish. Signs would be located approximately every 300 to 600 feet along Steamboat Slough and Ebey Slough. The Tulalip Tribes or the potentially responsible parties (PRPs) would be responsible for installing any required new signs. Following construction of the on-source cover system, natural recovery would reduce the concentrations of organics and inorganics. Inspections of the site would be performed to ensure the warning signs were still in place and readable. The Tulalip Tribes would be responsible for maintenance and enforcement of the signs. Periodic monitoring of the impacted sediment and seep soil is already required by the interim remedial action ROD. Monitoring would ensure the contaminants were attenuating and not migrating or increasing in concentrations.

Estimated Capital Cost: $15,410
Estimated Annual O&M Cost: Not Documented
Estimated Present Worth Cost: Not Documented
Text:  View full-text ROD [ 77K ]
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