Jan 30 2008
Grassy Island is located in the Detroit River near Wyandotte. For years, the U.S. Army Corps of Engineers used the island as a contaminated disposal facility. They constructed dikes and placed contaminated dredge from the River Rouge within the dike complex.
The island is closed to public access, but boaters do not always heed this rule. Also, fishermen and women and boaters are often in close proximity to the island. So, a health study was conducted and here is what was found, according to the Downriver News-Herald:
Grassy Island, a former diked disposal facility in the Detroit River near Wyandotte, apparently poses no health risks, provided some common sense precautions are taken.
The Army Corps of Engineers had built dikes around the island and placed dredged material there from the Rouge River from 1960 to 1982. As a result, the island’s soils contain elevated levels of polychlorinated biphenyls, polycyclic aromatic hydrocarbons and metals.
Public access to the island is prohibited, but as the report acknowledges, trespassers occasionally go there. Government officials continue to discourage boaters from trespassing on the island, but findings indicate that the island’s near-surface soil does not pose a health hazard.
“There is an overflow weir on the northeast end of the island that poses an attractive nuisance and possible drowning hazard for children. The slopes of the dikes are steep, which may cause people walking on them to slip and fall. The riprap on the shore makes disembarking treacherous for boaters who might dock at the island.”
Here is the full News-Herald story:
Here are some interesting Grassy Island tidbits that I found while scanning the full document:
In the past, pesticide and PCB residues have been detected in the flesh of waterfowl sampled from the island. There are no plans to develop wetland or waterfowl habitat on the island. Until contaminant concentrations in resident deer are known, consuming venison taken from the island, if the herd is thinned, should be prohibited.
Lastly, the dikes enclosing Grassy Island were constructed without engineering controls considered standard today. The integrity of the dike walls is questionable. Inspection and mitigation plans should be in place to prevent a failure of the dikes.
It should be noted that the Grassy Island facility, the first diked disposal facility operated by the COE in the Great Lakes, was built without engineered dikes and did not incorporate the features (liners, caps, riprap protection, etc.) of later structures (Best et al. 1992). Rather, the original six-foot dike was river bottom material composed of uncompacted clay, sand, and gravel (Manny 1999a).
In 1971, the COE increased the capacity of Grassy Island by constructing a 20-foot dike within the perimeter of the original six-foot dike. The COE stopped using the island for disposal following a 1982 rupture in the south dike wall. The COE repaired the rupture and reinforced the dikes along the navigation channel (east side of the island) with filter cloth and riprap to prevent further failure.
Here is the link for the entire document: