Riverbank collapse should be call to action

Sediment cleanup needs to be accelerated, say Ken Drouillard, Alice Grgicak-mannion, John Hartig, Joel Gagnon, Chris Weisener and R. Michael Mckay.

A portion of the riverbank at the former Revere Copper and Brass site collapsed Nov 27, releasing unknown quantities of aggregate and possibly contaminated soils into the Detroit River. The site was formerly listed by the U.S. Department of Energy (DOE) and the U.S. Environmental Protection Agency (EPA) as contaminated owing to past use of radiological materials for the Manhattan Project.

The site is now under lease by Detroit Bulk Storage, which uses the property to store aggregates and it was under its oversight that the shoreline collapsed.

The release of aggregates and adjacent soils from a hazardous site caused initial concerns about radiological contamination and threats to drinking water intakes downstream of the facility. Radiological assessments completed by DOE in 1989 did not show radiation above background and this was confirmed by Michigan Department of Environment, Great Lakes and Energy (EGLE), which sampled soils on location Dec. 6.

EGLE also collected water samples to determine other chemicals of concern, but not all the information from this sampling is yet available.

Another concern is the disturbance of contaminated sediments located underwater adjacent to the site. Rapidly sinking aggregates would have resuspended materials from the river bottom. This would further disperse contaminants downstream and lead to a greater spread.

Surveys by the Great Lakes Institute for Environmental Research, University of Windsor, revealed that sediments in this section of the river are highly contaminated with metals, polycyclic aromatic hydrocarbons and polychlorinated biphenyls.

There is an interpolation of contaminated sediments in the area of the breach. Some contamination indicates high probable toxicity to invertebrates (insects) living in sediments. In addition, contaminants at levels present are capable of promoting fish tumours and contributing to restrictions of fish consumption.

Surveys conducted by EPA and EGLE in 2013 confirmed contaminated sediments in this area. Indeed, the nearshore region surrounding the site, covering more than 570,000 cubic metres is designated by EGLE as one of nine priority areas in the Detroit River targeted for sediment cleanup.

There is no information on the impact of sediment disturbance or redistribution of contaminated particles that occurred due to this incident. In addition, ongoing salvage and reclamation efforts may further re-suspend sediments adding to contaminant mobilization.

Lastly, the delay by a week in followup water sampling after the breach is disconcerting. The water residence time in the Detroit River is less than 24 hours and any suspended particles would have been flushed downstream within minutes.

Given the predominant north to south direction of flow coupled with high flow rates, it is likely that much of the resuspended material would have moved along the U.S. shoreline potentially settling near the Rouge River outlet or downstream into Trenton Channel.

Although the likelihood of particles entering drinking water intakes from this location is low, had there been hazards caused by the incident, they would have not been detected during water sampling owing to delays in monitoring.

EPA and EGLE have done an exemplary job mapping contaminated sediment deposits and designating priority areas for cleanup in the Detroit River. However, the shoreline breach at the former Revere Copper and Brass Site highlights how vulnerable contaminated deposits are to shoreline activities and to human induced or other disturbances to the river bottom.

This incident should be a call to action to accelerate sediment cleanup at all designated areas in the Detroit River.

Ken Drouillard, Joel Gagnon, Chris Weisener and R. Michael Mckay are professors, Alice Grgicak-mannion is a geospatial learning specialist and faculty and John Hartig is a visiting scholar with the Great Lakes Institute for Environmental Research, University of Windsor.