Portland Harbor: Remediation of a Superfund Sediment Mega Site
The Portland Harbor Superfund Site has become one of the largest and most complex remediation efforts of its kind. It is commonly referred to as a sediment "mega site," and contamination in the Willamette River was detected as early as the 1920s. An investigation of river sediments, conducted in 1998 under the joint purview of the U.S. Environmental Protection Agency (EPA) and the Oregon Department of Environmental Quality (DEQ), revealed a host of embedded pollutants in the lower Willamette River that included the pesticide DDT and other hazardous and potentially carcinogenic compounds. Three years later, as a direct result of the 1998 study, EPA added a 10-mile stretch of the river near Portland’s north side to its list of national Superfund sites. CDM Smith has been providing EPA with technical support services since 2007 as the agency works with state and federal natural resource groups, 120 potentially responsible parties (PRPs), and six federally-recognized tribal governments to agree on individual remediation designs and action plans for the target areas.
The lower Willamette River is a migratory corridor and rearing habitat for multiple endangered species of fish, including Chinook salmon and Steelhead trout. The region also plays a key role in serving cultural, economic, and recreational needs. Because of the potential impacts of the pollutants on the river’s natural resources, EPA declared the site in need of “immediate and intense” attention and a national advocacy group named the Willamette one of the top 10 most endangered rivers in the U.S.
The official site is composed of approximately 2,200 acres of river over a 10-mile reach, 365 acres of which is contaminated sediment requiring remedial construction in one of the busiest shipping lanes in the United States. Starting in the middle of the 19th century, the harbor has served as the state’s major industrial corridor. Starting at Waldo Lake in central Oregon, the Willamette travels through Eugene, Salem and Portland, effectively linking together the state’s major population centers. Just before it empties into the Columbia River, on the border of Washington State, the Willamette winds around Portland’s highly industrialized northwest shoreline, which supports a mix of active commercial enterprises, from manufacturers to foundries, fuel oil dealers and beyond. It’s here where a diverse mix of public and private entities have come together to solve the area’s legacy of sediment contamination.
The reduced risk and exposure to toxins within the sediment will make the surrounding communities a safer and cleaner place to live, work and play in.
From the beginning, EPA understood the inherent challenges to performing an accurate and useful site feasibility study within such densely populated and highly trafficked boundaries. Site feasibility studies involve careful evaluation of waterway use, the extent of contamination, chemical fate and transport, source consideration and a complete characterization of sediment chemistry and toxicity. In Portland Harbor, contamination originated from a mix of direct discharges, as well as releases and spills from commercial operations over many years. Activities along the shoreline contributing hazardous compounds included ship building, wood treatment, lumber milling, bulk fuel storage, manufactured gas production, chemical manufacturing, metal production and recycling, smelting, and electrical production and distribution.
Following several years of preliminary investigations, EPA enlisted CDM Smith to help with technical support for the site’s feasibility study, which included detailed review and oversight of all groundwater, stormwater and riverbank studies. As part of the review, the CDM Smith team of sediment specialists has:
- assessed contaminant distribution and identified critical areas of contamination
- integrated upland source control evaluations and designs with sediment remediation activities
- reviewed, evaluated, and tested early action remedial options to ensure the proposed approaches would be successful in preventing upland sources from further contaminating water sediments
- worked with EPA and U.S. Army Corps of Engineers to develop and implement a remedial technology assignment approach based on site-specific physical, chemical, land, and water use characteristics
EPA released a comprehensive feasibility study, followed by a draft of the cleanup plan, public hearings, and an official Record of Decision in 2017. The remedy is expected to cost $1.05 billion dollars over 13 years and includes dredging and capping contaminated soil along a 10-mile stretch of the Willamette River combined with monitored natural recovery, a remediation tactic that relies on natural and ongoing deposition of cleaner sediments to reduce toxicity levels. This combined approach is expected to reduce cancer risk from exposure to contaminated sediment by 100 times the current level.
“The reduced risk and exposure to toxins within the sediment will make the surrounding communities a safer and cleaner place to live, work and play in,” said CDM Smith project manager Scott Coffey.
CDM Smith continues to support EPA as the agency develops remedial design guidance for the harbor that will inform critical design elements and ensure consistency sitewide.