Gas Works Sediment Area
Floyd|Snider is assisting the City of Seattle, through Seattle Public Utilities, with environmental investigations and remedy planning for sediments in the Gas Works Sediment Area, located offshore of Gas Works Park. Gas Works Park is the former location of manufactured gas, tar refining. and fuel handling facilities, and is located on the north shore of Lake Union, a heavily developed urban lake north of downtown Seattle. This site is highly visible, with intense public and stakeholder interest, due to its location and use as a public park. Floyd|Snider is currently managing the technical consultant team and providing scientific and engineering expertise in support of the Remedial Investigation and Feasibility Study (RI/FS) for the 27-acre Western Study Area. Floyd|Snider is also providing technical review of Eastern Study Area RI/FS documents, sediment source control evaluations, support to PLP coordination activities, public involvement, and City management processes.
Before initiating the RI/FS, Floyd|Snider performed environmental investigations and advanced remedy planning for the Gas Works Sediment Area. Prior to the execution of an Agreed Order between the Department of Ecology, the City of Seattle, and Puget Sound Energy (PSE), Floyd|Snider worked with PSE’s consultants to compile existing sediment data, correct errors within Ecology’s SEDQUAL database relevant to site data, and delineate a technically defensible Area of Investigation offshore of the park. Floyd|Snider also supported City and PSE efforts to develop methods and strategies for coordinating technical work between the Eastern Study Area, which is led by PSE, and the Western Study Area, led by the City. The Agreed Order formalized this separation into two study areas.
Floyd|Snider developed a Current Situation Report and RI/FS Work Plan that identified data gaps and highlighted the technical and political complexities of the Western Study Area. These complexities include the presence of free-phase tars in the sediments, overlapping sediment impacts from adjacent facilities, and intense public interest due in part to the site's central location and use as a park. Floyd|Snider provided oversight for implementation of the RI/FS Work Plan in Summer 2005. The sediment investigation included 16 surface grabs, 22 environmental cores, and geotechnical sampling and testing. Floyd|Snider then produced a Data Report for submittal to Ecology. Floyd|Snider just completed a screening level evaluation of Gas Works Park conveyance systems. This evaluation included a video survey of all accessible conveyance structures within and adjacent to the Park, and sampling of available and accessible catchbasin solids. Current work on the Western Study Area RI/FS is projected to continue into the Fall of 2009.
- Remedial Investigation/Feasibility Study
- Contaminant Fate and Transport Analysis (DNAPL)
- Source control
- Agency coordination and negotiation
- Remedy design and remedial cost estimation
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