Three Mile Lake work progresses as its water gains attention

With Three Mile Lake water being used by Southern Iowa Rural Water Association and the upcoming season for recreation, state officials are not expecting the lake to be less than desirable for all who use it as improvements are ongoing.

Iowa Department of Natural Resources Lake Restoration Program Coordinator George Antoniou said the state is continuing its diverse lake improvement project from shoreline to sediment flow.

“For a project for us at this scale, it seems like it’s been moving forward well. There are no big surprises for us,” he said.

Work started in fall 2023 with plan to be finished in spring 2025. Work includes improvements to 1.9 miles of shoreline, or 15 % of shore.

“That is critical, we have eroding banks of the lake that means a water quality issue from sediment,” he said.

The silt deck as part of the main arm that comes into lake will be raised to slow the flow of sediment into the lake.

“The upper area has served its useful life,” he said. Three Mile Lake has about a 20,000 acre watershed, meaning water from those acres eventually reaches the lake.

“That is a large drainage area into the lake,” he said.

Another planned project include jetty access work to help people get closer to the lake and improve fishing experience. Plans are to also improve fish spawning areas.

“Work is progressing, but the focus now is on the shoreline and we are about one-third done,” Antoniou said.

The work comes at an intriguing time as Three Mile Lake water is being used by Southern Iowa Rural Water Association at its treatment plant plus the time of year for more recreation at the lake.

“We are in periodic contact with SIRWA,” Antoniou said. “A few years back when this work was thought of, we knew of the city of Creston and SIRWA. We will keep open communication and milestone dates.” Last Friday’s heavy storms did not damage the DNR’s work at the lake. Union County Conservation is planning to build two, new cabins at the lake this year. That will not impede on the state’s work, Antoniou said.

Initially DNR wanted the lake lowered 11 feet for its work. Antoniou said further review showed most of the work could be done by only lowering the level 8 feet.

“In the fall we will come down another three. Some can’t be done until it’s down 11 feet,” he said.

Rains the past week have increased water level at Three Mile by about a foot, but Antoniou said the additional water is not a problem.

“Instead of opening the valve, we will let the lake naturally work its way with evaporation and SIRWA,” he said.

Antoniou said those who use the lake for boating and fishing should not have a different feel either.

“We will leave the main boat ramp accessible throughout project. We tell people to still watch knowing the water level. We still want people to access the lake.”

The state had done some work in fall 2021 including silt basins and stream enhancements.

“We were focused on making a good job for sediment retention and some stabilization streams were eroding,” he said.

In 2007, the lake itself was about 810 acres and had about 13,000 acre feet of water. An acre foot of water is the amount of water one foot in depth over one acre. When measured in 2019, it had reduced to 793 acres and closer to 12,000 acre feet of water because of the silt accumulation.