Ann Arbor reaches partial agreement with state over Argo Dam concerns

This aerial photo shows the earthen embankment that extends to the east from the concrete portion of Argo Dam.

City officials met earlier this week with the Michigan Department of Natural Resources and Environment to discuss vegetation concerns that were first raised by the MDNRE in a safety order last August. The city has been disputing the state's claims and recently hired a consultant to conduct a study that concluded there was no threat of failure, contrary to what was suggested by the MDNRE.

City officials said the brush being removed consists primarily of non-native invasive species.

"These deep-rooted woody plants obscure the toe drains and embankment, making routine inspections difficult," the city stated in a press release. "The root systems of the plants also cause a shift in the groundwater flow in and through the embankment, potentially compromising the stability of the embankment. Because of this, the MDNRE asserts that earthen embankments must be free of woody vegetation."

The city also must develop a vegetation management plan that will include both short- and long-term strategies for managing all of the woody vegetation on the embankment.

The city plans to submit a draft plan to the MDNRE in the next two weeks for review and approval. Negotiations on the remaining items in the dam safety order issued last August will continue once the city demonstrates substantial progress in removing the dead and overhanging trees and woody brush.

The city plans to have crews begin working on the embankment on Thursday, and needs to demonstrate substantial progress to the MDNRE within the next 30 to 45 days. 

Currently, the headrace remains closed, city officials said.

Ryan J. Stanton covers government for AnnArbor.com. Reach him at ryanstanton@annarbor.com or 734-623-2529.