For the past 68 years, the Heart River levee system has fit the bill when it comes to protecting Mandan and a portion of its outskirts from flooding.
However, the Federal Emergency Management Agency recently ruled the levee falls short of its modified criteria in the case of an ice jam during a 100-year run-off event.
To ensure the levee doesn’t lose its FEMA accreditation, an estimated $36 million worth of improvements is planned, with construction tentatively scheduled to begin in 2021.
Without the improvements, significant portions of Mandan — both residential and commercial — would be placed in the 100-year floodplain, without levee accreditation, and flood insurance would be required for buildings with mortgages from federally regulated or insured lenders.
“This project will be cheaper for home and business owners than them having to pay for flood insurance,” said Bill Robinson, chairman of the Lower Heart River Water Resource District.
Potential improvements to the levee system, which stretches from the second railroad bridge west of Mandan through the city to where the Heart and Missouri rivers connect, include moving the embankment at the Youth Correctional Center side to the west and widening the path about 30 yards from the Highway 6 bridge to Sitting Bull bridge.
An overflow channel would then be built to bypass the trolley bridge and curved area south of the bridge for water to flow in the event of an ice jam.
The aim of the project, according to Robinson, is to maintain property values, eliminate the need for flood insurance, spur development and protect investments.
FEMA indicated that, if the project moves forward as planned, the levee, which is composed of three sections — the lower unit, the Mandan unit and the Sunny unit — will not lose its accreditation.
“FEMA has sort of paused and is giving us time and space to get this project completed as we sit right now,” said Robinson.
Without improvements, if a flood were to occur due to an ice jam, about 1,800 Mandan properties would be impacted, with damages to buildings, contents and inventory estimated at $218 million, according to city officials.
The LHRWRD is working with the State Water Commission for a cost-share program of about $15 million. In addition, $100,000 is being sought from FEMA. The remaining balance will be paid by stakeholders, Robinson said.