Portland Harbor Source Control

The City operates multiple stormwater conveyance systems that discharge into the Portland Harbor Superfund Site in the lower Willamette River. Drainage areas for these systems include industrial, commercial, residential, and municipal properties, as well as open space. Some types of land uses can contribute chemicals to stormwater runoff, which discharges to the Willamette River.

GSI helped the City implement a stormwater source investigation program to identify and address stormwater issues on properties within its stormwater basins. Working closely with City staff and the Oregon Department of Environmental Quality, GSI helped identify properties that contribute unacceptable contamination to the City’s stormwater conveyance system. GSI provided technical support to ensure that problems at the identified properties were properly documented and plans were developed to control contaminant releases to the City’s stormwater system. This source control investigation work has helped regulators identify what source control actions (best management practices and engineering retrofits) are needed at upland sites.

GSI’s work has involved:

• Determining the configuration of stormwater collection systems and identifying connections to the City’s conveyance system based on engineering drawings and as-builts.
• Assessing whether pipes could receive groundwater inflow based on stormwater pipe invert elevation, as-built drawings, and local groundwater conditions.
• Evaluating upland site activities and environmental data to trace chemical sources of contaminants detected in the City stormwater system.
• Providing regulatory analysis.