Lower Duwamish Waterway
Source Control Investigation

Click on map to view larger size.West Riverside Drive
River Mile 2.2 to 3.4

Site Background 

The Riverside Drive source control area is located along the western side of the Lower Duwamish Waterway (LDW) Superfund Site between RM 2.2 to 3.4 as measured from the southern end of Harbor Island.
 
The aerial photograph shows the area of interest. Properties from RM 2.2 to 2.6 West include the Douglas Management Company and Boyer Towing/Logistics.  These were discussed in the EAA-2 Supplemental Data Gaps Reports for each facility. For the purpose of this report, the Riverside Drive source control area includes adjacent and upland properties from RM 2.6 to 3.4 West.
 
There are 68 upland properties that could potentially affect sediments in the RM 2.6 to 3.4 West source control area. Residential properties are located adjacent to the LDW from RM 3.1 to 3.4 West.  Facilities in the 8th Avenue S CSO basin are another potential sediment recontamination source.

Contamination

Sediments in the Riverside Drive portion of the LDW have been affected by chemical contaminants from various sources. Before reaching the LDW sediments, the contaminants first affected upland media including surface water, groundwater, soil, and air.
 
The following chemicals are contaminants of concern in the Riverside Drive source control area because they could possibly recontaminate Lower Duwamish Waterway sediments after cleanup.

Metals Organics
Mercury Polychlorinated biphenyls (PCBs)
  Polynuclear Aromatic Hydrocarbons (PAHs)
  Dioxins/Furans  
  Pesticides
  Phthalates
  Other semi-volatile organic compounds

Source Control

Ecology is the lead for source control for the LDW Superfund site. Source control is the process of finding and then stopping or reducing as much as possible releases of pollution to the river.  Potential sources of sediment recontamination associated with the Riverside Drive source control area include SDs, CSO outfalls, and discharges from adjacent and upland properties. Transport pathways that could contribute to the recontamination of sediments associated with the Riverside Drive source control area following remedial activities include direct discharges via outfalls, surface runoff (sheet flow) from adjacent properties, bank erosion, groundwater discharges, air deposition, and spills directly to the LDW. 

Source Control Action Plan

Ecology developed a Source Control Action Plan for the Riverside Drive source control area. This plan describes the source control actions that are necessary to reduce the potential for sediment recontamination. As part of the Source Control Action Plan, Ecology hired a contractor to produce a Summary of Existing Information and Data Gaps report.

Related Information

Additional Resources