Lower Heart Levee Project Anticipated to go to bid as Early as Fall 2025

Nov. 26, 2024 —Mandan City Commissioners recently approved acceptance of a Federal Emergency Management Agency (FEMA) grant for phase I of the Lower Heart Flood Risk Reduction project. This phase of the award provides funding for the completion of final engineering and designs plans, final benefit cost analysis, and any environmental compliance/permitting required for the final project.

Phase II will be the construction phase of the project, and additional federal funding will be approved for that phase at a later date. Groundwork cannot begin until Phase I has been completed and Phase II is officially approved by FEMA.

Background. A 2012 study performed by FEMA shows the Heart River levee system is insufficient for continued accreditation in the event of an ice jam during a 100-year run-off event. A follow-up study conducted in 2018 by the Lower Heart Water Resource District (LHWRD) and approved by FEMA significantly reduced the required remedial work, but did not eliminate all of the necessary improvements. The levee system runs from the second railroad bridge west of Mandan through the city to where the Heart River connects with the Missouri River.

This project includes replacing a concrete floodwall, raising the top of the levee in certain reaches, extending a stability berm, seepage remediation and incorporating interior drainage improvements. The benefitted areas of this project are almost entirely within the city of Mandan and its extra territorial jurisdiction. Several critical infrastructure features are included in the protected area, such as Mandan police and fire stations, city administration, public works facility, wastewater treatment plant and many more. Therefore, the project will provide benefits to the entire community by assuring the uninterrupted services of these infrastructure facilities.

Cost. Total project cost is estimated at $24.5 million. The estimated federal funds going towards the project is $13.8 million. The state of North Dakota is also putting $5.1 million towards the project, and the local share is $5.5 million.

In 2022, the City Commission approved a city-wide special assessment for this project. Both commercial and residential properties are included in the district in two different tiers:

• Tier 1 is the area that would be inundated in a potential flood from the Heart River (anticipated assessment for commercial $2,200; residential $1,700 per property)
• Tier 2 is the rest of the city (anticipated assessment for commercial $529; residential $423 per property)

The estimates above are from when the anticipated local share was $7.7 million. Since then, the City and LHWRD has been able to obtain additional grant monies and the local share has decreased to $5.5 million. City staff anticipates the special assessment costs for commercial and residential properties in both tier 1 and tier 2 to decrease by about 20%. The special assessments would be payable over a 15-year period (ex: amount assessed divided by 15 years = cost/year).

Timeline. In Feb. 2022, the assessment district was created; the bid package is anticipated to go out in the fall of 2025 or spring of 2026; construction would take place in 2026 and 2027; and the project would wrap-up in 2028. If the project follows this timeline, property owners would see special assessments on property tax statements in late 2028.

A potential impact for Mandan could be on Mandan Municipal Golf Course, specifically along hole four (on the west side of the course). LHWRD, City and Park District staff are working on identifying steps to be the least impactful to the golf course while providing this critical flood protection to the community.

Lower Heart History. The Lower Heart levee system was installed by the U.S. Army Corps of Engineers (USACE) and is managed by the LHWRD. The levee dates back to 1949 and has provided flood protection during numerous flood events. A persistent issue Mandan has faced is ice jams, which can unexpectedly and rapidly raise the water surface elevations of the river and induce flooding that would not normally occur.

The LHWRD is a board appointed by the Morton County Commission that manages 12,200 acres with 45% of its acreage in Mandan, 25% in the extra territorial jurisdiction and 30% in Morton County. The funding for the LHWRD is provided each year through Morton County and has a maximum allocation of four mills annually.

More info. Additional information on this project will soon be available on the project website at mortonnd.org/lowerheartwaterdistrict.