High Island Lake Water Control Structure Replacement

Background

High Island Lake, located in south-central Minnesota, has long been a destination for boaters, fishers, ice anglers, and others. In 2018, the lake partially drained when a leak developed under the existing water control structure. In March of 2019, the outlet completely failed.

The failure, while thankfully not a threat to human life or property, made the job of managing the lake much more difficult. The Minnesota Department of Natural Resources (DNR) had largely lost the ability to manage the lake’s water level, and nuisance aquatic species, including common carp that had been eradicated or reduced, had reentered the lake.

The DNR had initiated a project to repair or replace the existing structure after the initial leak was discovered in 2018. The failure in 2019 removed a repair from the options available to the DNR, and a full replacement of the water control structure was necessary.

The Project

HEI was retained to provide a recommended design for the replacement of the water control structure at High Island Lake.

The project team completed a siting assessment as well as an extensive hydrologic and hydraulic analysis. With this information and more, the team developed multiple water control structure options that would return water levels for the lake to typical elevations.

A fish barrier was included in the design of the new structure to prevent common carp from entering High Island Lake. Common carp are an invasive species that compete against desirable sport fish and stir up lake sediments, resulting in degraded water quality.

Construction was completed in 2022. The new outlet structure consists of a 120-foot sheet pile weir, 500 feet of earthen berm, and a 20-foot control section with stop logs and fish screens. The stop log structure allows the DNR to drawdown the lake to control invasive species per the lake’s management plan. After construction in 2022 and a successful winter drawdown, the lake was stocked with 100,000 walleye fry in the spring of 2023 to return sport fishing to the lake.