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Lac qui Parle Dam Emergency Spillway; Watson, Minnesota

Published April 16, 2020
Updated: April 16, 2020
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 over topping 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 7 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 rip rap on the downstream side to reduce scour. The bituminous surface of County Hwy 33 makes up the top of the spillway.

While the spillway has experienced overtopping events in 1997, 2001, 2009, 2010, 2011 and 2019 the spring flood of 2019 was the longest duration event. The result is that the grouted rip rap failed by water entering cracks along the road shoulder and eroding the road shoulder and supporting soils under the rip rap.

Status

The St. Paul District developed a scope of work for an Architect and Engineering (A-E) firm to evaluate the options for the project and recommend alternatives. The second phase of the project will be to utilize an A-E firm to develop the plans and specifications and subsequently advertise the project for construction and award a project. As a result of the fact that the spillway was constructed by the WPA and is eligible to be listed on the National Register of Historic Places, State Historic Preservation Office coordination is required.

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.

FY 2020:
Alternatives Analysis/Design                          $315,000

FY 2021:
Design (est)                                                       $132,000
E&D/S&A (est)                                                   $148,300
Construction Contract (est)                         $2,500,000