Two shallow landslides have occurred on the west side of CSAH 17 north of the TH 12 bridge over the South Fork of the Crow River in Delano, Minnesota. The head scarp was only a few feet away from the curb and gutter section of the road, jeopardizing infrastructure and safety. Wright County hired the SRF/Gale-Tec team to perform a feasibility and alternative analysis for potential repair options.
Gale-Tec conducted Global Stability Analyses for various configurations, while SRF conducted hydraulic modeling, shear analysis calculations, and permit investigations. Early coordination with the regulatory agencies, and an understanding of permit requirements of each, helped to further inform the feasible alternatives. Three viable options were developed through an iterative process.
The County preferred an option that included a Federal Emergency Management Agency (FEMA) non-certified sheet pile wall with a concrete coping along the top. This option allowed for the protection height to be increased without having adverse impacts to the channel conveyance and FEMA floodplain. The sheet pile wall serves as slope stabilization and as a floodwater diversion. The sheet pile ties into a recently constructed berm adjacent to the failure site, creating a continuous flood protection barrier along the east embankment.
The SRF/Gale-Tec team developed construction documents and helped work through construction challenges, including high voltage overhead lines that impacted sheet pile placement. SRF coordinated with permitting agencies (DNR, USACE, and FEMA) to ensure final design details, configurations, and construction methods adhered to agency requirements, and successfully obtained all required permits, including a ‘No-Rise’ certification.