Likely point of closure for the millrace (also known as the headrace or canal) at Argo Dam. (Photo by the writer.)

As part of an intro to an interview with the chair of the Ann Arbor Park Advisory Commission, Scott Rosencrans, which The Chronicle published on Aug. 25, we reported that a letter from the Michigan Department of Environmental Quality had been sent to the city of Ann Arbor. The MDEQ letter included an order to close the millrace at Argo Dam.

The communication from the state agency didn’t come out of the blue – it was a reply to a request sent to MDEQ by the city of Ann Arbor asking for an extension to a July 31, 2009 deadline for action on Argo Dam.

With the text of both letters now available, we take a look at those communications, after briefly considering some historical context. That context dates back to a 2004 letter from the MDEQ about toe drains in the earthen berm next to the dam, and includes formation of a study committee, a public engagement process that extended over most of the first half of this year, recommendations from the city’s Park Advisory Commission and Environmental Commission, and a city council work session.

A key date from the most recent MDEQ letter is Nov. 1, 2009, by which time it has ordered the city of Ann Arbor to close off and drain the millrace. But it leaves both the dam-in and dam-out options available to the city. On a dam-in scenario, the MDEQ wants the toe drains in the earthen berm repaired by Dec. 31, 2010. On a dam-out scenario, the MDEQ wants the removal completed by December 2012. Either way, the city is supposed to have its study of options completed by April 30, 2010.

Based on a Tuesday phone conversation with Matt Naud, the city’s environmental coordinator, one possible timeline for next steps would have the city council conducting a mid-September work session on the topic, with clear direction coming at the council’s second meeting in September. Whatever that direction from council is, said Naud, it’s going to start costing money to implement the next steps – on the order of five-figure dollar amounts at least.

Background

The following timeline is not meant to be exhaustive, but does convey at least that the issue with the toe drains in the earthen berm (headrace embankment) adjacent to Argo Dam has been of concern to the MDEQ for a long time and that the city of Ann Arbor’s response has unfolded in the form of a task force, public engagement, and consideration by city commissions and the city council.

The two basic scenarios under consideration are these: (i) Dam-out – find an alternative venue for the rowers who use Argo Pond and remove Argo Dam, or (ii) Dam-in – repair the toe drains in the earthen berm adjacent to the dam and develop a program for maintenance of Argo Pond.

• 2001 Inspection report from MDEQ notes problem with toe drains in earthen embankment.
• Nov. 18, 2004 A letter from the MDEQ references the 2001 inspection report that first pointed out problems with toe drains: “The inspection report for the Argo Dam identifies problems that may threaten its safety. Specifically, the toe drains along the downstream side of the raceway canal embankment are failing. The toe drain failure is complicated by the dense growth of trees and brush on the raceway embankment and by the inability to block the flow of water into the raceway during an emergency. The toe drain system should be repaired immediately, and a means of blocking flow into the raceway canal should be devised as soon as possible.”
• March 2006 The city’s Environmental Commission creates the Huron River and Impoundment Management Plan (HRIMP) committee
• Sept. 12, 2007 The assessment of the dam’s condition and recommendations in the dam safety report includes: “The principal spillway and main embankment of the Argo Dam are in good condition. However, the headrace embankment is in poor condition. The dam has adequate spillway capacity to pass the design flood. The following recommended actions are listed by priority. (1.) Submit a copy of the contingency plan to block off flow from the millrace by February 29, 2008. (2.) Remove overhanging and dead trees from the headrace embankment by July 31, 2008. …”
• Dec. 26, 2007 A letter from the DEQ includes the following: “The headrace embankment of the Argo Dam is in poor condition, and the toe drains are not totally functional. This has been described in past reports, and you have received a permit to perform repairs to the toe drain system. It is our understanding that this work has not been done yet, and discussion is ongoing regarding the future disposition of the dam.”
• March 24, 2008 A letter from the DEQ includes the following: “One of the recommendations of this report was that a contingency plan be developed to rapidly shut off flow to the headrace in the event of concerns over the headrace. You provide this contingency plan to this office in your letter of February 21, 2008. The contingency plan lacks detail on how an actual or impending failure of the headrace embankment would be determined. … [P]lease be reminded that this headrace contingency plan is intended to be a short term plan to alleviate potential impacts caused by a headrace embankment failure. It does not address the significant structural concerns with the headrace embankment.”
• January-February 2009 City staff conduct a series of public meetings. [Chronicle coverage of a public meeting at Forsythe Middle School.]
• April 28, 2009 The final version of HRIMP report is finished. Key conclusion: “The decision at the Argo area comes down to one of community preference. Both options will require significant investment of capital and operation and maintenance dollars in addition to staff time.”
• May 19, 2009 The city’s Park Advisory Commission recommends on a narrow 1-vote margin to retain the Argo Dam. [Chronicle coverage of PAC Argo Dam discussion.]
• May 28, 2009 The city’s Environmental Commission recommends removal of the dam. [Chronicle coverage of EC Argo Dam discussion.]
• June 15, 2009 At a work session conducted by the city council, the apparent consensus was that staff should be directed to identify questions that would need to be studied for dam-in and dam-out scenarios and to ask DEQ for additional time.
• July 16, 2009 Ann Arbor sends a letter to MDEQ outlining specific areas of study for the dam-in and dam-out options, and asks for an extension of the deadline until April 2010.
• Aug. 6, 2009 MDEQ sends a letter in reply granting the extension, but ordering the closure and dewatering of the headrace.

Additional Chronicle coverage: “Huron River of Data” and “Dam Questions Dominate Caucus.”

City’s Letter: July 16, 2009

Discussion at the city council’s June work session reflected the fact that from this point forward, the city would need to start spending money – either for additional study or to implement a solution. And money spent on additional study could be allocated most efficiently by electing to explore primarily either a dam-in or a dam-out solution. Otherwise put, continuing to consider both alternatives equally would not be as cost-efficient as making at least a preliminary decision one way or the other.

So in the city’s response to the DEQ, specific relevant areas of further study were identified for dam-in and dam-out scenarios. In some cases there’s overlap. For example, both scenarios see detailed bathymetry as helpful. But on a dam-in scenario, the idea of that analysis is to create a baseline model for future sedimentation modeling; on a dam-out scenario, the idea of the bathymetry includes a model of the shape of the new river channel after dam removal.

From the city’s July 16, 2009 letter to the DEQ, here’s a list of the dam-in areas of study:

Dam-In Areas for Further Study

Sediment analysis – The City plans to undertake a sediment study to determine the extent of sediment and estimate future sediment management costs if the impoundment is preserved.

Detailed Bathymetry – The City plans to undertake a detailed bathymetric analysis of the impoundment to create a baseline model of the impoundment for future sedimentation monitoring.

Hydropower Options – The Veterans Administration is evaluating reintroduction of hydropower at one or more Ann Arbor dam(s) and we would like time to see how their interest develops and whether this interest and investment affects the decision by City Council.

Environmental Consequences of Impoundment Preservation – The city plans to review the available data and obtain new data in key areas to create a baseline for monitoring the impoundment effects on river water quality and ecosystem services.

Economic Consequences of Impoundment Preservation – From these studies, the city will estimate long-term dam maintenance costs and develop cost-sharing plans.

Outside Funding Sources – City staff will evaluate alternate funding sources for rebuilding the millrace to remove the canoe portage. Due to current economic conditions, any decision will be based on our ability to leverage outside resources so identifying viable outside funding sources is critical to any City Council decision. Recent federal support for the Great Lakes is a $400 million opportunity that we need to evaluate.

River Flow Evaluations – Variations in flow at the USGS gauge at Wall Street are of concern to MDNR and the city is evaluating mechanisms to reduce the variability from Barton and Argo to better meet run-of-the-river conditions.

From the city’s July 16, 2009 letter to the MDEQ, these are the dam-out areas of study:

Dam-Out Areas for Further Study

Sediment analysis – The city plans to undertake a sediment study to determine the extent of sediment affected by dam removal and estimate sediment management costs as part of this analysis.

Detailed Bathymetry – The City plans to undertake a detailed bathymetric analysis of the impoundment to answer several questions including the shape of the new river channel.

Detailed HEC-RAS model – The city plans to use the detailed bathymetry to develop a detailed HEC-RAS model to answer several outstanding questions including how the floodplain may change.

Rowing – Because the rowing community is most adversely affected by dam removal, City staff will be evaluating two alternative rowing venues to determine if they are viable sites for rowing. We believe that it will take some time to work out the details at one or more sites.

Environmental Consequences of Dam Removal – The city plans to review the available data and obtain new data in key areas to better understand the changes in river water quality and ecosystem services.

Economic Consequences of Dam Removal – Develop more detailed economic analysis of dam removal including new recreation opportunities and costs and reallocation of existing funding to other projects.

Outside Funding Sources – City staff will evaluate alternate funding sources for dam removal. Due to current economic conditions, any decision will be based on our ability to leverage outside resources so identifying viable outside funding sources is critical to any City Council decision. Recent federal support for the Great Lakes is a $400 million opportunity that we need to evaluate.

River Flow Evaluations – Variations in flow at the USGS gauge at Wall Street are of concern to MDNR and the city is evaluating mechanisms to reduce the variability from Barton and Argo to better meet run-of-the-river conditions.

MDEQ’s Letter: August 6, 2009

In the letter from MDEQ, dated August 6, 2009, the state agency orders the city of Ann Arbor to do the following:

1. On or before November 1, 2009, completely shut off the flow from the impoundment to the headrace and dewater the headrace. The headrace shall remain dewatered until the headrace embankment deficiencies have been corrected in a manner approved by the LWMD or the dam has been removed. The City shall continue to monitor the seepage emanating from the embankment at least monthly and notify this office if it worsens or is found to transport solids. This monitoring may be discontinued upon approval by this office, if the seepage ceases upon dewatering of the headrace.
2. On or before April 30, 2010, complete an evaluation of the options to address the deficiencies of the headrace embankment of the dam.
3. If the decision is made to keep the dam in place, all work to correct the headrace embankment deficiencies in a manner approved by the LWMD must be completed by December 31, 2010.
4. If the decision is made to remove the dam, the removal shall be completed by December 31, 2012. The City shall complete all necessary engineering design work for the removal and submit and application for the removal to this department by February 1, 2011.
5. The City shall submit reports on its progress to comply with this order annually by August 15 of each year until the deficiencies with the headrace embankment have been corrected.

The Nov. 1 deadline for closing the millrace (headrace) comes after the last date indicated on the city of Ann Arbor’s website for canoe rental from the city’s liveries, which is Sunday, Oct. 25, 2009. Through what little remains of this season, then, there might be little impact on the revenues about which Scott Rosencrans had expressed concern in his Aug. 20 interview.

Based on The Chronicle’s telephone conversation with Naud, closing off the millrace is fairly straightforward – a metal plate gets slid into place. But draining the millrace – or “dewatering” it, in the parlance of the MDEQ – is something that’s somewhat more complex, Naud said. The fact that the resulting empty millrace could pose a potential hazard to the public was, said Naud, “not a new thought.” Naud characterized how to deal with that – possibly through fencing it off – as a still-outstanding question. If a decision were made to fence it off, Naud said, it’d be a straightforward matter to calculate how much fencing was required and to price it out.

Naud sketched out one possible timeline for decision-making that would start the city in one direction or the other – at least in terms of what study options were pursued – on the dam-in dam-out question. That sketch would see the city council conduct a work session in mid-September on the dam question. Then at their second September meeting (Sept. 21) they might give some clear direction, say in the form of a resolution authorizing an expenditure.

If the city council does take up the topic of the dam at a September work session, it will need to add the dam to a joint work session already planned with the city’s planning commission to discuss zoning revisions (A2D2). At the city council’s last meeting, the idea of adding a discussion of council rules and ethics to the work session’s agenda was rejected.

Millrace at Argo Dam looking downstream from the point where the millrace allows canoeists to exit Argo Pond. (Photo by the writer.)

View from east to west. Canoeists currently paddle down the millrace from the right, and take their boats out of the water and down the steps indicated by the sign at the left. (Photo by the writer.)