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Record of Decision System (RODS)

PACIFIC SOUND RESOURCES

Abstract

Site Name:  PACIFIC SOUND RESOURCES
Address:   
City & State:  SEATTLE  WA  98126
County:  KING
 
EPA ID:  WAD009248287
EPA Region:  10
 
NPL Status:  Currently on the Final NPL
 
ROD Type:  Record of Decision
ROD ID:  EPA/541/R-99/083
ROD Date:  09/30/1999
Operable Unit(s):  02
 
Media:  Groundwater, Liquid Waste, Sediment, Soil
 
Contaminant:  Base Neutral Acids, Dioxins/Dibenzofurans, Metals, PAH, PCBs, Pesticides
 
Abstract:  The Pacific Sound Resources (PSR) facility, formerly known as the Wyckoff West Seattle Wood Treating facility, was located on the south shore of Elliott Bay in Puget Sound at 2801 S.W. Florida Street, Seattle, Washington. Wood-treating operations were conducted at the site from 1909 to 1994. The wood-treating facility occupied approximately 25 upland acres. The southern portion of the facility (10 acres) was used primarily for treated wood storage, and the northern portion of the facility (15 acres) was used for processing. All retorts, product storage tanks and piping were located on the northern portion of the facility. The wood-treating chemicals used at the PSR site included creosote, pentachlorophenol, and various metals-based solutions. Soil, groundwater and off-shore marine sediments have all been impacted by the facility's operation.

The wood-treating plant started as a pile-supported facility over the Duwamish River estuary. The shoreline and intertidal area was filled in at various times throughout the last 100 years, and the facility was eventually entirely located on fill-material that created an upland. This in-filling resulted in the border between the upland and off-shore area being a steep riprap bank. The site is located in an industrial area on the south shore of Elliott Bay.

EPA conducted two phases of early cleanup actions on the upland portion of the site. The first phase focused on site stabilization and demolition of on-site structures. The second phase focused on controlling on-going sources to Elliott Bay, addressing contaminated soil, and preparing the site for reuse by the Port of Seattle (Port). During the first phase in 1995, the entire wood treatment facility was demolished and approximately 4,000 cubic yards of highly contaminated soil and process sludge were removed from the site. During the second phase, which began in 1996, a subsurface physical containment barrier (slurry wall) was installed to prevent light non-aqueous phase liquid (LNAPL) migration to Elliott Bay, and to reduce the influence of tidal fluctuation at the site. The slurry wall is 1,200 feet in length and it extends from the ground surface to a depth that averages 40 feet below ground surface. An LNAPL recovery trench was installed in conjunction with the barrier wall to intercept any LNAPL. In addition, a low-permeability asphalt cap was constructed over a layer of clean fill placed at the site. This cap was designed to prevent direct soil exposure to on-site workers, prevent runoff of contaminated soil to Elliott Bay, and minimize infiltration of storm water to groundwater. The cap was completed in 1998.

The Upland Unit remedial investigation/feasability study (RI/FS) began in 1994 and focused on groundwater, including non-aqueous phase liquid (NAPL) contamination. The Marine Sediments Unit RI/FS began in 1996 and focused on marine sediment contamination. Human health and ecological risk assessments were conducted for both the upland and off-shore areas. The PSR site was added to the National Priorities List in May 1994.

A Record of Decision addressing both units was signed in September 1999.
 
Remedy:  The selected remedy includes finalizing the early actions taken at the Uplands Unit. Early cleanup actions were completed to address threats posed by contaminated soil and groundwater and shallow non-aquious phase liquid (NAPL) in the Upland Unit. Included in these actions were the installation of a subsurface containment wall and light NAPL(LNAPL) collection trench along the northern site perimeter and the placement of a low-permeability surface cap over the Upland Unit. The subsurface slurry wall was designed to minimize flow of contaminated groundwater and LNAPL to Elliott Bay and reduce tidal influence on contaminant movement below ground surface. The purpose of the cap was to isolate contaminated soil and reduce groundwater recharge (and associated contaminant mobilization). Early actions were completed prior to the remedial investigation/feasibility study (RI/FS) process.

Two general response actions were considered for subsurface containment: hydraulic containment and physical containment. Physical containment was selected primarily because LNAPL seeps to Elliott Bay could be prevented. Three types of physical containment technologies were evaluated: sheetpiles, slurry walls, and grout curtains. Grout curtains were eliminated on technical feasibility concerns; the integrity of curtains in heterogeneous fill conditions and high groundwater tables is uncertain. Slurry wall technology was selected rather than sheet pile technology due to its lower cost. The final remedial action selected was the implementation of an upland hanging slurry wall.

PSR groundwater meets cleanup requirements under the National Contingency Plan (NCP) and threshold requirements for cleanup actions under the Model Toxics Control Act (MTCA) without implementation of additional engineered remedial measures. What was selected as an early action is the final action, and the development and detailed evaluation of a series of cleanup alternatives was not required for the Upland Unit. Requirements to ensure Upland Unit actions remain proactive include engineering controls, institutional controls, and monitoring.

The Selected Remedy for the Marine Sediments Unit is:

Confinement (through capping) of contaminated marine sediments that exceed the cleanup screening level (CSL) for polycyclic aromatic hydrocarbons (PAHs) for the sediment quality standard (SQS) for polychlorinated biphenyls (PCBs). The sediment quality standard (SQS) for pentachlorophenol (PCP) will be used to trigger cleanup for sediment at depths equal to or shallower than -10 feet mean lower low water (MLLW). The capped area will encompass approximately 50 acres of contaminated sediment.

Dredging of approximately 3,500 cubic yards of contaminated sediment from the area to the north of Crowley Marine Services. The purpose of dredging this material is to maintain current navigational depths and access to Crowley Marine Services. The dredged material will be disposed of in an established upland solid waste landfill. Unused pilings throughout the Marine Sediments Unit will be removed prior to capping. The pilings will be cut at the mudline and clean cap material placed over the portion remaining in the sediment.

The clean capping material used will be at least as clean or cleaner than the SQS and will be obtained from routine maintenance dredge projects in local rivers. In addition, capping material will be selected and placed in such a way as to provide appropriate habitat for the marine organisms natural to this area.

The entire capped area will be designated as a "no-anchor" zone. The no-anchor designation will apply to commercial vessels using the large "whale-tail" type anchors that have the capacity to break through the cap and expose contaminated sediment.

Estimated Capital Cost: Not Documented
Estimated Annual O&M Cost: Not Documented
Estimated Present Worth Cost: $7,600,000
 
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