whether to tear down the ninety-five-year-old dam or repair an old earthen embankment attached to it. According to Matt Naud, Ann Arbor's environmental coordinator, either way it's going to cost city taxpayers $250,000 to $500,000.
Engineers at the MDEQ Dam Safety Program aren't worried about Argo Dam itself, which they say is in good condition. The problem is a 1,450-foot-long earthen embankment built to divert water from Argo Pond to a hydroelectric plant by the Broadway Bridge. The plant no longer operates, but the millrace is used by canoeists to portage around Argo Dam, and joggers use a dirt path on top of the embankment to reach trails around Argo Pond.
MDEQ engineers say the city must clear the ten-foot-wide embankment of brush and trees and clean out or replace about sixty drainage pipes, called toe drains, which keep water from building up inside the embankment. Most of the toe drains are clogged, buried, or missing, according to Byron Lane, chief of the Dam Safety Program. Without functional toe drains, he says, the embankment is in danger of becoming saturated and collapsing, especially if a tree falls over and pulls a big chunk of dirt out with it.
"Our concern is that the dam could fail, releasing the entire contents of the impoundment pond in a flood wave downriver," Lane says. "In Ann Arbor's case, there are occupied buildings downstream from that dam. You're talking about a hazard that could affect people's lives and property."