A New Drain in an Old Pond: Creative Solution to Infrastructure Management
The Michigan Association of County Drain Commissioners (MACDC) recently presented Evan Pratt, P.E., the Washtenaw County Water Resources Commissioner, with an Innovation and Excellence Award for the Tyler Dam Drain Project.
Newly reconstructed Tyler Dam Drain channel.
A Combination of Issues
On the eastern edge of Washtenaw County, in Ypsilanti Charter Township, are two now-defunct factories that once churned out automobile parts and B-24 Liberator bombers during WWII. The Willow Run Creek meanders between these properties, and in the 1940’s, a dam was built along the creek to create a stormwater impoundment pond in a natural ravine.
This impoundment was called Tyler Pond and provided water for the factories to fight fires. When the plants closed, the Tyler Dam was passed to Ypsilanti Charter Township.
Spanning the width of Tyler Pond were two sanitary sewer mains built in the 1970’s that were supported by a timber trestle bridge. The 24-inch gravity sewer and a 36-inch force main connect to a pump station along Airport Road in Ypsilanti Charter Township and a nearby wastewater treatment plant. The Ypsilanti Community Utilities Authority (YCUA) owns and operates the sanitary sewer lines and the wastewater treatment plant.
Spicer Group was hired by YCUA to conduct a structural analysis of the aging trestle bridges and developed several different options to replace or repair the trestle structure. Around the same time, safety inspections of the Tyler Dam identified potentially costly repairs that were needed to bring the dam up to safety standards.
Ypsilanti Charter Township had also begun investigating removing or decommissioning the dam structure to prevent long-term maintenance costs and decided to permanently dewater the impoundment through a pipe under the dam, leaving the dam in place. This solution allowed the dam to be decommissioned, minimizing future maintenance costs, and did not require full dam removal, which would have been a significant additional expense. After Tyler Pond was dewatered, the natural channel would be restored to the ravine.
Reconstructed and armored storm sewer outfall.
Partnering for a Solution
To aid in the completion of both projects, Ypsilanti Charter Township contacted Evan Pratt, P.E., Washtenaw County Water Resource Commissioner (WCWRC) to follow the procedure of establishing the Tyler Pond as a new county drain, the Tyler Dam Drain, in Washtenaw County, as laid out in the Michigan Drain Code.
After receiving an application and petition from the Township to establish a portion of the Willow Run Creek as a county drain, the WCWRC office held a Board of Determination Hearing. Spicer Group presented the history of the Tyler Pond and the engineering observations on decommissioning the dam and establishing the new drain.
The Board then found it necessary to proceed with establishing this portion of the creek as a new county drain. Petitioning the WCWRC to establish this portion as a county drain facilitated the necessary permitting and funding to be in place to make these projects a reality.
Beginning the Transformation
The WCWRC hired Spicer Group to design improvements that would transform Tyler Pond into a county drain. Spicer Group created a solution that incorporated the decommissioning of the dam, drawing down Tyler Pond, and replacing the failing utility trestle.
“Preliminary design had already been started on stream restoration,” Evan Pratt, P.E., said. “We and the Township were both thrilled that the Spicer team found over $750,000 worth of value-engineered savings from existing estimates.”
Due to different funding streams being used, the three different projects were bundled together.
“This was a situation where it was a real benefit to have one consultant managing all of the overlaps between design, permitting, and developing contracts to make it easier to assign costs to different funding sources,” Pratt said. “EGLE was also very accommodating by taking time to work together on the best permitting process for the big picture. It also helped that a single contractor won all divisions.”
In order to construct within the original Tyler Pond area, a cofferdam was constructed around the Tyler Dam to allow crews to draw the water down six inches per day, as dictated by the permit issued for the project, which took several months to complete.
The trestle was replaced with a nearly 18-foot-high berm and large-diameter arch culvert structure that stretched over the newly established drain and was used to bury YCUA’s sanitary sewer pipes above the drain safely. This saved a considerable amount of money compared to boring or constructing a new trestle.
The embankment around the culvert was armored to allow for short-term re-watering of the impoundment during extreme rain events. Large amounts of heavy riprap and fabric were used, and the existing clay material from areas around the drain were used to stabilize the embankment under the utility lines.
The newly-exposed ravine was then reconstructed into a natural two-stage channel county drain by excavating a new channel through the sediment, which had accumulated in the pond bottom.
To prevent erosion and promote the overall drain health and water quality, biodegradable contour wattles were used after the drain banks were constructed, and substantial riprap was put into place.
Additionally, more than a dozen outfalls from nearby residential and commercial areas were extended outwards into reinforced and armored channels. French drains were also implemented to reinforce the channel’s drainage capacity and prevent soil erosion. Heavy riprap was then placed along the drain bank for reinforcement. Live staking was placed along the banks, and various seed mixtures were used to preserve their shape and protect against erosion.
Benefits to the Environment
The newly-established Tyler Dam Drain carries stormwater from upstream lands, which are a mix of roadways, residential, and commercial uses, into the Willow Run Creek and ultimately into Belleville Lake.
Before this project, the only improvements that had been made to the area was a dredging of the pond to remove contaminated soils by the Environmental Protection Agency in the 1990’s. The existing stormwater outlets were in poor condition and undersized for flow now coming through them.
Spicer Group designed this project to create a free-flowing drain with a two-stage channel that allows for improved water quality downstream and an environment more conducive to native wildlife.
Crews placed more than 1,160 square yards of heavy riprap on the newly-formed drain banks for reinforcement. This helped stabilize the channel in areas of steeper slopes and protected the banks against the high-velocity water that flows into the drain from the extended and reinforced outfalls.
The drain center was also designed to follow the naturally-formed ravine, and a meandering low-flow channel was designed to reduce overall sediment transport into Belleville Lake.
More than 5,000 live stakes and plant plugs were installed along the drain banks to reduce the risk of severe erosion. These plant plugs take root and help protect and stabilize the drain banks. A riparian seed mix was also used, which takes root and grows better under wet soil conditions.
Funding the Fix
Developing the Tyler Pond into the Tyler Dam Drain allowed the WCWRC to use Special Assessment funds to facilitate the necessary drain work needed. This made the project of decommissioning the dam and building the culvert over the drain cost-effective.
Funding for the overall project was a mixture of State Revolving Funds for the utility culvert and associated utility work, Township funding for some limited work on the dam, and Special Assessment funds for the drain work. Due to sound legal advice in 1980 when the upstream Beyer Dam was accepted by Washtenaw, a strong negotiating position allowed for contributions from a redeveloped industrial site to offset property owner costs. Because the district is the largest low-income part of the County, Pratt said it was very helpful going into the Hearing of Necessity knowing that the project would be funded with no drain assessments to property owners.
Now that the project is finished, this area will cost less for the WCWRC to maintain, the Township will not have to expend funds to maintain the dam, and the buried utility lines across the culvert are easier and safer for YCUA to maintain.
Finished Tyler Dam Drain bed with live-stake growth.