Lower Duwamish Waterway
Source Control Investigation

West Restoration Areas
River Mile (RM) 4.2-5.8

SITE BACKGROUND

Click on map for larger size.The Restoration Areas source control area is located along the western side of the Lower Duwamish Waterway (LDW) Superfund Site between River Mile (RM) 4.2 to 5.8 as measured from the southern end of Harbor Island.

The aerial photograph shows the area of interest. There are twenty-four upland properties in the Hamm Creek drainage that could potentially affect RM 4.2 to 5.8 West sediments.  Properties adjacent to the waterway in this source control area include the Hamm Creek Restoration Area, Seattle City Light (SCL) Power Substation, Kenco Marine Restoration Area, Turning Basin 3 Restoration Area, Thales Avionics, Mellon Desimone Trust (MDT) Properties, Boeing D&SG Oxbow Site, United States Postal Service (USPS) Distribution Center, and North Wind’s Weir Restoration Area.

CONTAMINATION

Sediments in the Restoration Areas portion of the LDW have been impacted by chemical contaminants from various sources. Before reaching the LDW sediments, the contaminants may have affected other media including surface water, groundwater, soil, and air.

The following chemicals are considered to be contaminants of concern in the Restoration Areas source control area.

Metals Organics
Arsenic Polychlorinated biphenyls (PCBs)
Cadmium Polynuclear Aromatic Hydrocarbons (PAHs)
Silver Dioxins/Furans
Pesticides
Phthalates
Phenols
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 contamination associated with the source control area include discharges from adjacent and upland properties. Transport pathways that could contribute to the contamination of sediments associated with the Restoration Areas source control area 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 hired a contractor to put together a Summary of Existing Information and Data Gaps report.  Ecology and its contractor used the report to develop a Source Control Action Plan for the Restoration Areas source control area. This plan describes the source control actions that are necessary to reduce the potential for sediment contamination.

Related Information

Additional Resources