Portage/Base Line Lakes
The Washtenaw County Water Resources Commissioner’s Office operates Flook Dam, just downstream of Portage and Base Line Lakes, as part of a legally established lake level. The dam, constructed in 1965, controls water levels in the lakes through the use of 5 radial gates separated by concrete piers.
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Flook Dam Informational Meeting
Since the last update...
Please note that we will be lowering the lake to winter levels starting on November 21, 2023.
This will involve placing boards upstream of two more gates, with the result that 4 of the 5 bays will be offline at least through the winter months. The middle gate will be used to adjust the lake elevation, which is our normal procedure each year.
Thank you to all the residents for providing input on possible sources of white oak lumber. This will be necessary to help provide a safe working environment in each bay as the gates are removed and replaced. Our office is happy to report we have found a lumber mill to fabricate these boards and expect to take delivery in early December.
Since the last update…
- Our office has been in conversations with various milling operations to fabricate oak boards.
- These boards will be used to stop the flow of water through the bays when the gates are removed for replacement. They can also be dual-purposed during winter water levels to help prevent the existing gates from icing or further deterioration.
- After the repairs are complete we will be able to continue to use these boards for yearly dam operations.
- We conducted a public informational meeting to discuss the history of the dam, status of the gate failure and repair, the assessment district, and the assessment process.
- Formalize a contract with Spicer Group Engineering to have dam gates replaced and concrete work performed.
- Initiate steps to review and revise the assessment district and the properties contained within it.
Since the Last Update...
- Our consultant has created a two-phase detailed task outline with steps necessary to complete repairs and rehabilitate the dam.
- This list will serve as a checklist to ensure we do not overlook any items needed for a safe and complete conclusion to the dam project.
- The Livingston County Board of Commissioners is meeting this week to discuss a resolution to exceed the $10,000 annual maintenance limit.
- We are planning on having an informational meeting later this fall to provide updates to all interested parties about the legal process, the work completed to date, and the timeline for the repairs.
- Stay tuned for that announcement and mailings to all property owners liable for assessments on the lake level.
Since the Last Update...
- On August 2nd, The county Board of Commissioners passed a resolution allowing our office to exceed the annual $10,000 spending limit for lake-level operations.
- Our office met with our project engineer and our local fabricator to discuss some design options to temporarily remove some of the bays from service while they are being repaired.
- The engineering firm, Spicer Group, also met with a regional dam repair firm to obtain price estimates to replace the gates used in each of the bays.
- We will continue to collaborate with Livingston County on creating a comprehensive map of the assessment district for the lake level.
- We continue to collaborate with Livingston County to present their Board of Commissioners with a similar resolution allowing their county to also exceed the annual $10,000 spending limit.
- We will continue to operate the dam as necessary to keep the established lake level at its summer level.
Since the Last Update...
- We met with the state’s dam safety unit, along with a structural engineering expert, at the dam site last week.
- Regulatory guidance and suggestions for securing the dam gates until they can be permanently repaired were offered.
- A preliminary review has indicated that each of the five radial gates used to regulate the flow through the downstream ends of Portage and Baseline Lake need to be replaced due to overall loss of structural integrity.
- A two-staged approach will be used to correct this issue, but it appears we will be able to maintain court-mandated lake levels throughout the repair operations.
- The first stage will be to remove some of the gates from active service and take the corresponding bays offline. This will involve the use of additional boards or metal sheeting to restrict lake discharges to the active bays.
- We have requested the Washtenaw County Board of Commissioners to pass a resolution allowing our office to exceed the annual $10,000 spending limit for lake-level operations and maintenance. If passed, this will allow us to formally institute permanent repairs on the dam structure.
Next steps for the coming weeks:
- Fabricate reinforced boards or metal plating to place in the bays and remove further bays from service. The ability to adjust lake levels should not be affected by these measures.
- The Board of Commissioners' resolution will be discussed at the August 2nd meeting.
What has happened?
- Although routine inspections have indicated the overall structural stability of the dam is satisfactory, our office contacted a consultant with engineers that specialize in structural elements of waterway dams in April of this year to further analyze the integrity of the gate apertures and concrete abutments.
- While preparing to conduct an inspection one of the control arms on an outer gate failed, rendering the bay inoperable.
- We stabilized the situation by taking the control gate offline, and as a result of the subsequent inspection, also cordoned off another gate bay as a precautionary measure.
What does this affect?
- While the lake level can still be controlled through the use of the remaining three operational gates, please be advised that there may be somewhat longer periods of time following significant rain events to lower water levels to the legal standard.
- While we are diligently working with our engineering partner to prepare a final recommendation report and plan of action to renew the dam’s operations, we do not currently know the extent of repairs required nor do we know the timeframe in which to fully restore the dam’s capabilities.
- We request your patience and understanding as we work through these issues, and will continue to provide updates as they become available.
Lake Levels Reports
Portage and Base Line lakes are located in Dexter and Webster Townships. The Lake Level District includes lands in both Washtenaw and Livingston County. Washtenaw County includes approximately 545 parcels in the assessment district. The Water Resources Commissioner’s Office actively monitors the level of the lake.
Established Lake Levels
Daily weather conditions affect the lake level and a 1-3 inches fluctuation outside of the established level is common. Low inflows from the watershed into the lakes are a result of minor drought conditions, while an increase of water into the lakes comes from quick or heavy rain. Any fluctuations outside of this norm are addressed within hours of notification.
The Portage Base Line Lake sensor gauge is located near the Flook Dam. This gauge is monitored by a Dam Operator 24/7. It is common to see higher lake levels upstream of this point during the wet seasons.
The lake level is drawn down each winter to reduce the ice damage to the shoreline. Lowering of the lake level is scheduled in coordination with the closing of the Department of Natural Resources boat launch on Portage Lake. Typically, the drawdown to the winter level begins mid-November.
Raising the lake level is dependent on the weather. The water must be free of ice cover and weather must remain consistently above freezing. Typically, the change to the summer level begins in late March or early April.
- The legally established summer lake level is 851.54 feet.
- The legally established winter lake level is a range between 850.04 feet and 850.29 feet.