
Meadows Stormwater Flood Mitigation
The Meadows Stormwater Flood Mitigation project addressed complications resulting from years of severe flooding events in Sidney, MT.
The Meadows Subdivision is located at the downstream end of a large drainage basin of nearly 1,000 acres that produces a significant amount of runoff. Residents in the subdivision have experienced severe flooding caused by rapid melting. The large basin contributes increased runoff volumes during rain and snow storms that overwhelm the existing culverts and spread stormwater through the neighborhood.
The most severe flooding occurred on February 8, 2015. While only 0.37 inches of precipitation was recorded, which is less than a 2-year rain event, the rapid snow melt in the basin caused significant volumes of runoff that inundated the drainage infrastructure and roadside ditches. The upgradient detention pond exceeded its capacity and released peak flows to the Meadows neighborhood. The pooling runoff threatened several homes in the area when it could not pass through the outfall culvert, which was already operating at maximum capacity. Volunteers from the community and fire department were onsite sandbagging and pumping water to prevent homes from flooding.
To mitigate the potential damages caused by stormwater flooding in the subdivision, the City of Sidney partnered with Morrison-Maierle to complete preliminary design and obtain grant funding for the stormwater improvements project. The project design includes modifications to the regional detention pond to increase storage and attenuate peak flows, new storm inlets, and a large diameter stormwater pipe to safely direct runoff out of the residential area.
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BRIC application
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Grant administration
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Hydraulic modeling
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Private and federal easements
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Stormwater flood mitigation design
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Survey



Funding – Building Resilient Infrastructure and Communities
Morrison-Maierle helped the City of Sidney prepare an application to FEMA’s Building Resilient Infrastructure and Communities (BRIC) grant program. This program provides up to 75% funding for projects that help communities withstand natural hazards. The grant application included a preliminary engineered design, modeling of potential flood damages, and a benefit-cost analysis.
The city was awarded $1.3 million to fund the engineering and construction of the stormwater project. In addition, a 25% local match—$500,000—was obtained from the State’s Resiliency Fund. These awards allow the project to be 100% funded by state and federal grants.
Design – Complex Hydraulics, Limited Space, Water Quality
The final engineering design includes a model that simulates the complex hydraulics present throughout the contributing drainage. The model includes a series of farm ponds in the upper reaches of the catchment area that provide limited storage and split flows that weave through the residential area in open channels and culverts.
Limited space and existing utilities in the Meadows Subdivision prevent the new storm drain from being installed within the road corridor. To address this issue, the new pipe will be installed on the edge of the subdivision adjacent to a USBR irrigation canal and will require coordinating with the USBR and local irrigation district.
Further benefits of this project—in addition to increasing the storage capacity of the existing detention pond—included a bioretention cell and pretreatment forebay to treat stormwater. This feature will also decrease maintenance by trapping sediment and allowing small storm events to infiltrate.
This Meadows Stormwater Flood Mitigation project will better equip subdivision residents to deal with significant rain, runoff, and stormwater situations.
Learn more about our stormwater work