A.53 Ottawa River, Canada

A.53.1 Summary

Environment:	Freshwater
Scale:
Contaminants of Concern:	PCBs: Some samples were as high as 74,000 ppm and fish concentrations as high as 500 ppm.   About 1/2 of the 104 sediment samples from the 28 cores contained PCBs at <50ppm.   Less than 10% of the samples contained PCBs >10,000 ppm
Final Remedy:	Excavated material was transported to a staging pad for gravity dewatering then fed into a pug mill via track hoe.   14,975 tons of dewatered, stabilized material were disposed as TSCA waste at Wayne Disposal facility in Bellvue, MI. 881 Tons of soil were disposed as nonhazardous waste at Evergreen RFD in Norwood, OH.   The material was mixed with 8–10% of pozzament 100, a stabilizing agent, to reduce free liquid, cured, then sent to a landfill.

A.53.2 Site Description

Year: 1998

Contaminated sediment area is a tributary that is 975 ft long and 90 ft wide at its mouth, and tapering to a 10 ft width at the origin.

Tributary Sediment (soft, silty) and adjacent wetland soils

Water Depth: 0–40 ft

Target Volume:

6,500 yd³ of sediment (from the tributary)

Actual Volume Removed:

8,039 yd³ (in situ) sediment

1,653 yd³ of wetlands soil

A.53.3 Remedial Objectives

PCB <50ppm

Sediment thickness: 5–15ft. 1ft of sediment was proposed to prepare the area for use in staging sediment removal equipment activities.

Dredged depths: 5–15 ft

Conventional earth moving equipment was used.

A.53.4 Remedial Approach

Existing storm sewer pipes that drain into the tributary were re-routed into a newly constructed 660 ft long stormwater channel.

A.53.5 Monitoring

Resuspension:

To hydraulically isolate the tributary from the Ottawa River, 164 linear feet of steel sheeting was installed at the mouth of the tributary. Water was pumped out and treated on site. This eliminated the tributary from acting as any sort of surface water flow channel.

Residuals:

Dredging event Area 1 current Level: <0.1 ppm PCB

Dredging event Area 2 current Level: 4.6 ppm PCB

Dredging event Area 3 current Level: 0.6 ppm PCB

Dredging event Area 4 current level: 0.5-38 ppm PCB

The tributary was backfilled with clean fill to a final design grade, covering any residual materials with at least 5 ft of backfill.

A.53.6 References

U.S. EPA. Great Lakes Act Project to Remove Polluted Sediment. Jan 2010. http://www.epa.gov/glla/ottawa/ottawastart.pdf.

U.S. EPA. Great Lakes Legacy Act Ottawa River Cleanup Has Begun. No. 10-OPA056. May 2010. http://yosemite.epa.gov/opa/admpress.nsf/0/9cb5fd7102773a51852577290052cc1b?OpenDocument.

Major Contaminated Sediment Sites Database; Sept. 2004 as updated 2008. http://www.smwg.org/MCSS_Database/MCSS_Database_Docs.html.

Publication Date: August 2014