Spillway collapse at Erity Dam results from unattended dam safety needs

On June 22 after unusually higher than normal seasonal amounts of rain, according to local officials, the right spillway of Erity Dam collapsed. Erity Dam is a 102-year-old concrete gravity dam on the River Rouge in Beverly Hills Village, Mich., a suburb of Detroit.

Inspection reports dating back to 2007 from both the Michigan Department of Environmental Quality (DEQ) and private engineering firm Hubbell, Roth & Clark gave no specific time period, but they indicated Erity Dam’s level of disrepair and lack of maintenance would lead to a structural failure.

No injuries resulted from the failure, but locally published reports said the spillway collapse caused the loss of several trees, “severe” erosion below the spillway and slight damage to nearby Evergreen Road.

DEQ and private sector engineers estimate costs to repair and maintain the dam range from US$250,000 to 3 million, according to Chris Wilson, village manager.

Additionally, Wilson said he has concerns that large amounts of water are passing underneath Evergreen Road, and the flow will likely undermine the road’s “safety and viability.”

In his 2009 report to the Beverly Hills Village council, Wilson wrote that the DEQ notified the village in December 2007 that the dam contained some structural deficiencies.

After being hired by Beverly Hills Village, in its May 2013 report to the village council, HR&C stated, “If left in their current state with no maintenance or dam removal, the structures will ultimately fail.”

Immediately after the collapse, Wilson said, “The DEQ had just come out earlier in the month [June 2015] and told us failure of the dam was imminent.”

Erity Dam is a gravity dam 16 ft in height and has a length of 240 ft. The dam creates Rouge River Pond, a 27-acre catchment area that has a 200 acre-feet maximum capacity. From it, the dam has a maximum discharge is 2,550 cubic feet per second.
 

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Gregory B. Poindexter formerly was an associate editor for HydroWorld.com.

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