Lac qui Parle Dam Emergency Spillway; Watson, Minnesota

U.S. Army Corps of Engineers, St. Paul District
Published April 16, 2020
Updated: March 22, 2022
Purpose

The Lac qui Parle dike and emergency spillway is designed to retain the Lac qui Parle Reservoir during times of flood but is designed for overtopping during extreme events. The overtop elevation of the spillway is 940.75 feet.

Location

The Lac qui Parle Dam is located on the upper Minnesota River 30 miles east of the South Dakota border. The dam is about seven river miles upstream of Montevideo, Minnesota. The dike and emergency spillway is adjacent to and west of the dam between the dam and County Hwy 75. The damaged area of the spillway extends approximately 2,500 feet from the dam.

Description

Like the rest of the Lac qui Parle flood damage reduction project, the dam and spillway construction was performed by the Work Progress Administration (WPA). Operation of the project was transferred from the state of Minnesota to the U.S. Army Corps of Engineers in 1950. The original authorized purposes were water conservation and flood control, but it is currently operated to include recreation, fish and wildlife, as well as water supply.

The dike and emergency spillway is a 2,500 foot earthen structure with a concrete I-wall on the upstream side to control seepage and hand-laid grouted riprap on the downstream side to reduce scour. The bituminous surface of County Hwy 33 makes up the top of the spillway.

While the spillway experienced overtopping events in 1997, 2001, 2009, 2010, 2011 and 2019, the spring flood of 2019 was the longest duration event. This resulted in deteriorating grouted riprap because of water entering cracks and eroding the road shoulder and supporting soils under the riprap.

Status

The spillway is eligible to be listed on the National Register of Historic Places and coordination with the State Historic Preservation Office is ongoing.

The St. Paul District awarded an Architecture and Engineering (A-E) Services contract to Stanley-Stantec JV to develop the plans and specifications.  The district will award a construction contract to repair the spillway in late 2022.

Authority

The dam is part of the Lac qui Parle Project authorized by the Flood Control Act of 1936 (Public Law 74‒738).

Funding

This project is funded with 2019 Emergency Supplemental Funding and fiscal year 2021-2022 work plan funds.

Design (est)                                   $600,000

E&D/S&A (est)                               $850,000

Construction Contract (est)     $7,100,000