Cass County Bridge No. 9
Cass County Bridge No. 9

Location:  Cass County
Client:  Cass County

Background

In recent years, residents of Maple River Township found a regular route across the Maple River inaccessible due to a bridge closure. Flooding in 2009 and 2010 damaged the bridge and with slope failures at the site from poor soil conditions, the bridge was deemed unsafe. While there are other routes across the river, they require long detours, costing local residents and farmers both time and money. A subsequent FEMA inspection determined that funding would only allow for the repair of one abutment. With the bridge in poor condition, the repair of a single abutment would not restore its integrity. Cass County then faced the challenge of replacing the entire structure with limited funding available.

The Project

The County enlisted Houston Engineering, Inc. (HEI) to help restore access to the area by designing a new crossing over the Maple River. In the interest of creating a reliable structure, but with the available FEMA funds taken into consideration, HEI designed a new low water crossing, a low-maintenance, low-cost solution for the County with flood protection in mind. This type of structure is rarely utilized in the area. This option eliminated the hefty costs of a new bridge, but still provided reliable service to local residents.  

The approaches to the culvert and the inslopes of the roadway were protected with concrete and riprap to prevent erosion and damage to the site during flooding or overtopping, thus decreasing the likelihood of erosion and slope deterioration. The erosion and slope deterioration previously had contributed to the prior bridge’s unsafe condition. In fact, the slope erosion and poor soil conditions at the original location mandated that HEI move the crossing a short distance upstream, requiring 1,700 feet of roadway realignment and construction. The crossing’s design and overtopping area will decrease headwater levels for major flood events, keeping the farmstead high and dry.

The crossing’s innovative use and design garnered the praise of The North Dakota Ready-Mix & Concrete Products Association, which awarded HEI and Cass County its Gold Star Award in the category of Design Innovation.

By creating this low water crossing in lieu of a new bridge, HEI eliminated roughly $200,000 from the project’s total estimated costs, making the crossing not only a safe and reliable travel option for local residents but an affordable one, as well.