Argo Dam mill race, still draining - beware of thin ice
Now that cold weather has set in, most of the mill race below Argo Dam has frozen over. The water level is way down from its normal height, and the stop log put in on November 2 has done its job of helping the city comply with the DEQ's order to remove water from the headrace.
A drain, partly clogged with debris, drains the Argo Dam millrace.
Edward Vielmetti | AnnArbor.com
At the time, the estimate was that the stop log would cause the level of the head race to go down by 3 feet. The surprise is that it's two months later and the mill race is still draining, through a newly exposed and still partially clogged drain. I had seen this drain in earlier visits to the dam when it was just barely submerged, and a few quick swipes with one of the many dead branches near the shore were enough to get the water flowing again.
Reader Russ Miller had alerted me to this drain in his reading of the 1992 Argo Dam safety inspection report, where it refers to a 12" pipe that runs to the tailrace for circulation. Two larger pipes, which had originally carried water that was turned into power in turbines, have been capped with concrete.
That report also refers to the many dead trees on the mill race embankment, recommending that they be removed - a recommendation repeated by each of the subsequent inspection reports I've seen.
Be alert that the ice along the shore near the drain in some places is more fragile than it would appear; there's still a bit of open water, and anywhere that water is flowing you don't want to trust the ice nearby. The draining water has left at least an inch gap between the ice and the water level nearest the drain. I walked on the ice last weekend but only further upstream near the Argo Dam proper and only near enough to the shore that I could be sure I would be near a tree branch. There were ski tracks on the ice from someone who had been more adventuresome.
It's a really pretty walk.
Edward Vielmetti is still looking for a place to safely play pond hockey for AnnArbor.com. Contact him at edwardvielmetti@annarbor.com.
Comments
water
Mon, Jan 4, 2010 : 4:05 p.m.
The Huron River Watershed Council (HRWC), along with others, explored the issue of the direction of the river downstream of Argo dam years ago when the issue of dam removal was being introduced and discussed. The DTE site is one of the most contaminated sites in the Huron. HRWC does not want to see the river's course being changed to flow over the DTE property. The environmental engineers and scientists we consulted with advised us that removing the dam does not mean that the river will reoccupy the old channel and I question where the science is to support that claim. I could not find any back-up information on that assertion. Below the dam is a drop pool to help dissipate the flow/drop of the river. The pool sits below the 15 foot dam. Yet when/if we remove Argo dam the 15 foot grade will be "regraded" and dispersed over a larger area than the dam. Rock veins (rock structures) in the river are placed above and below the dam to even out the elevation drop where the dam used to be and catch and store sediment. When you distribute the drop over a larger section of the river, the flow or force of the water will be reduced substantially. Initial reviews suggest that the current retaining wall will not see more pressure after dam removal. Granted we need to do further studies. There were some models completed in earlier studies, but let's be clear that City council is looking at moving in one direction or the other and that regardless we need further analysis of both options. Additional armoring of the retaining wall is also another option.