This Programmatic Environmental Impact Statement (PEIS) has been prepared for the Puget Sound Confined Disposal Site Study, an interagency effort led by the U.S. Army Corps of Engineers (Corps) and the Washington Departments of Ecology (Ecology) and Natural Resources (DNR). Other participating state and federal agencies and organizations include Puget Sound Water Quality Action Team (PSWQAT), Washington Public Ports Association, and Region 10 of the U.S. Environmental Protection Agency (EPA).
The objective of this PEIS is to provide a broad initial environmental review and cost analysis of major alternatives for the confined disposal of contaminated sediments dredged from Puget Sound, Washington. Pending the outcome of this evaluation of disposal alternatives, a site-specific EIS in support of a specific confined disposal alternative may be pursued in that region of Puget Sound that might benefit most from such an effort. The long-term goal of this effort is to address the regional need for confined disposal of contaminated sediments that require dredging and disposal. The alternatives evaluated at a programmatic level include the following:
Authority and Jurisdiction
This PEIS was prepared pursuant to the National Environmental Policy Act (NEPA) and the Washington State Environmental Policy Act (SEPA) to support federal, state, and local decision making in regards to the confined disposal of contaminated sediments. The Corps, Seattle District, is the NEPA lead agency for this project, and Ecology and DNR are the co-lead SEPA agencies.
The Corps has regulatory authority over many activities affecting the waters of the United States. This authority is derived from both Section 10 of the Rivers and Harbors Act of 1899 and Section 404 of the Clean Water Act (1977). A Section 10 permit is required for dredging operations of any kind whether for navigation or environmental cleanup. A Section 404 permit is required for discharges of dredged or fill material into waters of the U.S. including wetlands. This includes upland disposal environments when there is return flow (e.g., runoff) to the waters of the U.S.
For any federally permitted project that requires a Section 10/404 permit, Ecology has authority through Section 401 of the Clean Water Act to issue a water quality certification. A Section 401 certification is a precondition to receiving a Section 404 permit and is designed to ensure that the proposed action does not violate any applicable federal and state water quality criteria.
The dredging and confined disposal of contaminated sediments in Puget Sound also would need to comply with other state and local laws and regulations. In addition to the other agency study members (EPA, DNR, and PSWQAT), participating agencies and groups that might have authority over activities described in this PEIS, depending on the disposal alternative and geographic location, include the following:
Purpose and Need
The dredging of sediments from shipping channels and berths to maintain or deepen navigable water depths, from waterfront development and habitat restoration projects, and from aquatic site cleanup projects, results in a need to safely handle and dispose of dredged material that is unsuitable for unconfined, open-water disposal. These contaminated sediments require confined disposal to eliminate or minimize the risk of short- and long-term contaminant release to the environment.
To date in Puget Sound, dredging and disposal of contaminated sediments have been done on a project-by-project basis. The contaminated sediment dredging and disposal process can be time-consuming, expensive, uncertain, and often controversial for dredging proponents, regulators, and the public. Efforts to clean up contaminated sediments have also been hindered by the lack of viable confined disposal options and the time required to obtain project approval from permitting agencies. Thus, the overall goal of the Puget Sound Confined Disposal Site Study is to find environmentally sound and affordable solutions for the confined disposal of contaminated sediments.
Based on existing information, the volume of contaminated sediment in Puget Sound that will require confined disposal over the next 15 years, is projected to be between about 6 and 14 million cubic yards (cy). Subtracting the volume of sediment that will likely be cleaned up before a multiuser site could become available, from 4 to 10 million cy of contaminated dredged material from Puget Sound will require confined disposal. These estimates include sediment from contaminated site cleanup projects, navigation and maintenance dredging, waterfront development, and habitat restoration projects.
The majority of the contaminated sediments are located in Puget Sound’s south-central urban/industrial embayments. Considering all existing sites, about 44% of the contaminated sediment volume is located in the Elliott Bay/Seattle/Lake Washington area (including the Ship Canal and Lake Union). Another 21% is located in the Sinclair Inlet/Bremerton area and 20% is found in Commencement Bay. About 10% is in the Bellingham Bay region and the remaining relatively minor volumes are found in Port Gardner (4%) and Budd Inlet (1%). Because the Sinclair Inlet area is geographically close to the Elliott Bay region, about two-thirds of Puget Sound’s contaminated sediments are situated in this central Puget Sound area. This is the region with the greatest contaminated sediment disposal need and the logical focus for a site-specific confined disposal EIS.
As existing contaminated areas (which can be sources of contamination to adjacent areas) are cleaned up and as improved source control efforts continue to be implemented throughout Puget Sound, it is reasonable to assume that the input of contaminants to Puget Sound will decrease over the study’s planning horizon. Natural processes such as sedimentation (burial) and chemical and biological degradation should also reduce contaminant levels in surface sediments over time. Consequently, a long-term decrease in contaminated sediment disposal needs may be observed as the contaminated volumes identified above are addressed. Alternatively, delays in on-going cleanup actions and/or the adoption of more restrictive sediment cleanup standards could increase long-term contaminated sediment disposal needs.
Alternatives
Seven alternatives (including no-action) for the confined disposal of contaminated sediments from Puget Sound were identified by the study team. The major features of each alternative are described below. The constructed alternatives for multiuser disposal sites (MUDS), [level bottom capping and contained aquatic disposal, nearshore and upland confined disposal facilities (CDF)s] and the use of existing solid waste landfills are defined in the PEIS in sufficient detail to allow evaluation and comparison of their potential environmental impacts and cost elements. Much of this detail was based on information provided by the Corps’ Waterways Experiment Station for this study (Palermo et al. 1998a).
To allow evaluation of the constructed alternatives in this programmatic EIS, it was necessary to make assumptions about the design, shape, layout, capacity, and operational life of each alternative. For each constructed alternative, a conceptual design was developed and both 500,000-cy and 2,000,000-cy facilities were considered. Also, each facility was assumed to be operational (i.e., accept contaminated dredged material) for a 10-year period. It is important to note, however, that other realistic design and operational options exist. For example, a MUDS could have more than a 2,000,000-cy capacity and be in operation for more than 10 years. So while this PEIS presents and evaluates plausible scenarios for a Puget Sound MUDS, other reasonable scenarios could emerge during site-specific efforts.
No-action
Under the no-action alternative, no multiuser disposal site would be established. Contaminated sediment cleanup and dredged material disposal would continue as it is currently done. Confined disposal facilities would be developed by individual users on a project-by-project basis, some contaminated dredged material would likely be disposed in existing landfills, and some contaminated sediments would be left in-place and exposed to the environment until remedial action or dredging was required. These actions would likely be conducted under the existing framework of regulations and options. In addition, changes to existing policies or regulations might be pursued (i.e., even in the absence of additional confined disposal studies) to facilitate contaminated sediment disposal or cleanup. Examples of such changes are discussed briefly under the no-action alternative.
The following three alternatives are considered the main constructed alternatives because they include disposing of contaminated sediments in a constructed confined disposal facility (Figure S-1). For environmental impact evaluation, feasibility, and costing purposes, it is assumed that each constructed facility would have a 10-year operational life and both 500,000- and 2,000,000-cy capacity sites are considered.
Level Bottom Capping (LBC) and Contained Aquatic Disposal (CAD)
LBC and CAD are two types of underwater sediment disposal that are discussed as one alternative because they have similar features and potential environmental impacts. LBC is the placement of contaminated material in a mound on an existing flat or very gently sloping natural bottom and covering the mound with clean sediments. The cap isolates the marine environment from the contaminated material and minimizes the potential for contaminant migration. Biological communities recolonize these areas following final cap placement.
CAD is similar to LBC but includes some form of lateral confinement (e.g., placement in natural or excavated bottom depressions or behind berms) to minimize spread of the materials on the bottom (see Figure S-1). CAD is generally used where the bottom conditions (e.g., slopes) require lateral control measures to limit the spread of the contaminated sediments.
Both LBC and CAD include dredging of contaminated sediments from one or more locations, transportation to the disposal
site, and accurate placement of the contaminated materials at the site. LBC sites have been successfully constructed
on relatively flat bottoms (0-1%) in depths up to about 200 ft (Wiley 1995, SAIC 1998). CAD sites are generally
constructed in water depths less than or equal to 100 ft, but can be constructed in areas with slopes up to 6%.
Given the relatively steep slopes that are characteristic of the shallower depths in much of Puget Sound, the CAD
option was considered a more likely aquatic disposal scenario and was therefore developed as the aquatic alternative
conceptual design in this PEIS. However, this does not preclude consideration of a LBC design as part of future
site-specific confined disposal efforts if suitable site conditions exist.
The dredging, disposal, and monitoring technologies associated with LBC/CAD facilities are well-established. The effectiveness of an LBC/CAD facility in avoiding or minimizing environmental risks is a function of appropriate site location, design and construction, technology and operational controls, and effective short- and long-term monitoring and site closure. Two successful CAD projects have been completed in Puget Sound. In others areas of the U.S. and throughout the world, numerous effective CAD and LBC sites have been constructed.
For this PEIS, the conceptual design for this alternative consists of series of CAD pits that are excavated, backfilled with contaminated sediments, and capped with clean sediments (one CAD pit per year over the 10-year operational life). Cost estimates for disposal at the conceptual CAD site described in this PEIS range from $13/cy to $17/cy (exclusive of dredging and transport costs to the CAD site and land acquisition costs).
Nearshore Confined Disposal Facility
Nearshore confined disposal is the placement of contaminated dredged material at a site constructed partially or completely in water adjacent to shore, where the dredged material is contained by a dike or berm (see Figure S-1). Nearshore sites use the shoreline as part of the containment structure, with in-water dikes constructed out from the shoreline to complete the enclosure. Once the contaminated material filling the diked area reaches a specified elevation, it is capped with clean material. The clean capping material raises the elevation to just below or at dike level. The nearshore sites can be finished to grade to allow beneficial reuse or development of the created uplands after completion. Alternatively, they can be finished to grade in the intertidal zone to create intertidal or shallow subtidal habitat.
The construction, dredging, disposal, and monitoring technologies associated with nearshore disposal facilities are well-established. Three nearshore CDFs for contaminated sediments have been successfully constructed in Puget Sound in recent years. The effectiveness of a nearshore site in minimizing environmental risks is a function of appropriate site location, design and construction, operational controls, and effective long-term monitoring and site closure. The three Puget Sound CDFs, initially constructed in water, have become useful upland areas (e.g., container terminals) following final capping and closure.
The disposal cost estimates for nearshore CDF conceptual design described in this PEIS range from $27/cy to $44/cy
(exclusive of dredging and barge transport costs to the CDF).
Upland Confined Disposal Facility (including a Dewatering Facility)
The upland CDF alternative is the placement of contaminated sediments within a diked confinement structure. The contaminated sediments are covered with clean material to allow beneficial reuse after completion (see Figure S-1). Upland CDFs are designed to retain dredged sediment solids while providing acceptable suspended solids and/or contaminant concentrations in effluent for discharge to receiving waters. All dredged material at upland CDFs is placed above the water table.
Although there are currently no upland CDFs for contaminated sediments in the Puget Sound area, nationally, upland CDFs are one of the most common dredged material disposal methods. Upland CDFs are found throughout much of the country and are extensively used in the Atlantic and Gulf Coast regions of the U.S.
The technologies associated with constructing and disposing of sediments in an upland CDF are similar to solid waste landfill technologies (see below). In this PEIS, it was assumed that water content of the dredged sediments for disposal at both the upland CDF and solid waste landfill alternatives is reduced before disposal to minimize water management requirements at the facilities. The upland conceptual design includes dewatering of the contaminated sediments at a separate rehandling facility that is accessed from the water before transport and final placement at the upland CDF.
The dewatering facility is comprised of multiple cells where material can be actively disposed of, left for dewatering, rehandled for transport to the upland disposal site, or used to store excess sediments. Individual cells are lined or paved to control leachate infiltration into the groundwater, depending on regulatory requirements and the level of sediment contamination. Dikes of compacted soil or concrete provide the outside walls and separate the dewatering facility into individual cells. All water within the dewatering operations area is collected and treated to meet state and local water quality requirements before discharge back to surface waters.
The estimated costs for disposal at an upland CDF, including dewatering at specially established rehandling facilities, range from $47 to $63/cy (exclusive of dredging and transport costs to the dewatering facility).
Disposal in Existing Solid Waste Landfills
The solid waste landfill alternative is the placement of contaminated sediments within an existing upland solid waste landfill. Solid waste landfills in the state of Washington are regulated primarily by the Minimum Functional Standards For Solid Waste Handling (WAC 173-304), Criteria For Municipal Solid Waste Landfills (WAC 173-351), and the Resource Conservation and Recovery Act (RCRA) (Subtitle D). These regulations were established by state and federal governments to ensure protection of human health and the environment.
Sediments must be dewatered prior to transport to a landfill because of the water content in dredged material. Dewatering requires rehandling of the contaminated sediments at a facility that is accessed from the water and is typically included and permitted as part of a project dredging plan. Under this alternative, dewatering is done at a specially-constructed nearshore multiuser dewatering facility, as described in the upland CDF alternative.
The technologies for disposing of contaminated sediments in an existing solid waste landfill are well-established. The dewatered sediments are placed in lined containers for transport by truck or rail to a landfill. At the landfill, sediments are placed in an active cell for disposal or, if appropriate, used as daily cover material for other waste materials.
Private and public landfills currently operating in Washington and Oregon have accepted contaminated sediments for disposal. The two largest operating private landfills in the region are Roosevelt landfill in southern Washington, operated by the Regional Disposal Company of Rabanco, and Columbia Ridge landfill in northern Oregon, operated by Waste Management, Inc. In western Washington, county governments operate solid waste landfills for disposal of material generated within their jurisdictions. While many of these sites can accept dewatered contaminated sediments, the capacity of these landfills is limited. Because of the difficulty in siting new landfills near metropolitan areas, most Puget Sound basin jurisdictions are reluctant to accept a large volume of unanticipated material such as contaminated sediments.
The cost estimates for disposal at a solid waste landfill range from $48 to $65/cy. These estimates include dewatering, transport, and disposal at current landfill disposal costs for large quantities of material ( i.e., 500,000- and 2,000,000-cy), but are exclusive of dredging and transport costs to the dewatering facility.
Multiuser Access to Privately-Developed Confined Disposal Projects
This alternative calls for access to larger confined disposal projects by users other than the project proponent. Project proponents have been reluctant to provide multiuser access to their disposal projects because of the following concerns:
The environmental issues associated with multiuser access to a confined disposal project would be the same as for a multiuser facility of the same type (e.g., nearshore or upland). Some differences between the multiuser disposal alternatives and this alternative would be how long the site would be open for disposal to accommodate multiple users, how the liability would be managed for multiple parties, and how the site would be managed and operated. These issues would need to be addressed as part of a project- and site-specific environmental review.
Combination of Alternatives
A combination of two or more of the alternatives previously described is also an alternative. This alternative could be a hybrid composed of any of the action-based alternatives. For example, a CAD facility could be located adjacent to a nearshore CDF, or a location including both a nearshore and upland CDF could be developed. Siting and capacity criteria are critical elements in determining the feasibility of the combination alternative. Because a combination alternative would not be identified until after completion of the PEIS and initiation of the site-specific site selection process, the combination alternative is not directly evaluated in this PEIS. However, the environmental consequences and cost of any potential combination alternative can be assumed to be a composite of the consequences and costs of the individual alternatives.
Impacts and Mitigation
Table S-1 summarizes the potential impacts, mitigation, and unavoidable adverse impacts of each of the major alternatives. Impacts are associated with contaminant pathways and potential biological receptors. Mitigation involves controlling or minimizing the opportunities for contaminant release to the environment through effective siting, site design, technology and operational controls, site monitoring and management, and effective closure practices. Because the constructed alternatives involve the irretrievable commitment of aquatic, nearshore, and upland land resources to a sediment containment function, the siting process and decisions made during site-specific efforts will be critical in avoiding or minimizing significant impacts.
Conclusions
With the completion of this PEIS, the Puget Sound Confined Disposal Study will be at a critical decision point. The following issues will need to be addressed by the study team:
1) Based on the anticipated confined sediment disposal need, should the study team pursue one or more of the alternatives for Puget Sound and move forward with a site-specific confined disposal study in a selected region(s)? Based on existing dredging and disposal technology and regional and national experience in handling contaminated sediments and designing confined disposal facilities, which of the alternatives described in this PEIS are practicable?
2) In order to move forward with a preferred alternative or subset of alternatives, the advantages and disadvantages of each must be considered in a broader context that combines environmental impacts, cost, irretrievable commitments of public resources, ability to meet regional disposal needs, timing issues, policy and liability concerns, and public acceptability. Table S-2 summarizes some of the broader advantages, disadvantages, and areas of uncertainty for each alternative based on the information presented in this PEIS.
| Alternative | Potential Impact | Mitigation | Unavoidable Adverse Impacts |
| No Action |
|
|
|
| Contained Aquatic Disposal | |||
| CAD Cell Excavation and Contaminated Sediment Placement |
|
|
|
| Cap Placement |
|
|
|
| Long-term Containment |
|
|
|
| Nearshore Confined Disposal Facility | |||
| Site Preparation andCDF Construction |
|
|
|
| Contaminated SedimentPlacement and Redistribution |
|
|
|
| Cap Placement |
|
|
|
| Long-term Confinement |
|
|
|
| Upland Dewatering Facility and Confined Disposal Facility | |||
| Site Preparation andCDF Construction |
|
|
|
| Dewatering and Disposalat Upland CDF |
|
|
|
| Long-term Confinement at Upland CDF |
|
|
|
| Disposal in Existing Solid Waste Landfills | |||
| Dewatering and Overland Transport by Truck or Rail |
|
|
|
| Long-term Confinement at Existing Landfill |
|
|
|
| Multiuser Access to CDF |
|
||
| Combination of Alternatives |
|
| Alternative | Potential Advantages | Potential Disadvantages | Uncertainty/Controversy |
| No Action |
|
|
|
| LBC/CAD |
|
|
|
| Nearshore CDF |
|
|
|
| Upland CDF |
|
|
|
| Existing Landfills |
|
|
|
| Multiuser Access |
|
|
|
| Combinations |
|
|
|