The Vermillion River flooded CSAH 50 in Dakota County at the 10-year frequency, which was significantly below the acceptable level of service. In addition, the river is a designated trout stream, with trout habitat located within the affected reach. SRF provided final design services to upgrade the four-mile segment of roadway linking the communities of Lakeville and Farmington. We used the HEC-2 model and existing data to perform a detailed hydraulic analysis that balanced the proposed bridge opening with weir flow over the roadway. A variance was obtained from the Minnesota Department of Transportation to allow the new roadway to overtop at a frequency greater than the 25-year frequency. In addition to the waterway analysis for the river crossing, SRF’s water resources services included designing the following:
- Storm sewer within the urban segments of the project integrating water quality treatment prior to discharging to the river, which is a trout stream
- Cross culverts in rural areas to accommodate growth
- Box culvert in Lakeville to provide flood protection via roadway overtopping for the existing condition, while also providing hydraulic capacity through the culvert for the future condition
- Wetland mitigation site, receiving water from a detention basin and located adjacent to the Vermillion River
The project also involved coordination with communities to preserve and enhance trout habitat. Throughout the project, SRF worked with the Cities of Lakeville and Farmington to accommodate their plans future growth.