In early 2019, heavy rainfall triggered a landslide on the steep hillside between CSAH 14 and CSAH 21 in Scott County. The slope, which rises approximately 80 feet, had been channeling runoff through an 18-inch culvert beneath CSAH 14, exacerbating drainage pressures and slope instability.
Hydraulic and Geotechnical Analysis
SRF conducted a full hydrologic and hydraulic analysis of the broader drainage system, including the existing storm sewer infrastructure. Findings were detailed in a hydraulic engineering report used to support alternatives development and regulatory permitting. Geotechnical partner Gale-Tec performed subsurface exploration, testing, and slope stability evaluation.
Four stabilization alternatives were identified. The preferred solution combined a two-tier reinforced soil slope (RSS) wall with upgraded storm sewer infrastructure to improve both slope resilience and drainage conditions.
Temporary Stabilization and Emergency Planning
To keep CSAH 14 open through winter, SRF developed a temporary stabilization solution and construction plan set in fall 2019. This interim fix ensured public safety while final designs were underway.
Additional Washouts and Rapid Response
Just one day before bid opening in July 2020, another severe storm caused further slope failure and expanded the project boundaries significantly. The SRF team mobilized immediately, revisited the site, and updated the construction plans and State Aid Project Memorandum within five weeks—doubling material quantities and project scale. Permitting was re-coordinated with USACE, MnDNR, and NPDES.
Funding and Environmental Compliance
The expanded project received FEMA disaster funding and required NEPA clearance in addition to local and federal environmental permits. Despite the added complexity, SRF’s quick response and multidisciplinary coordination ensured project success on an accelerated timeline.
Internal Category:
Water & Environment
Municipal Services
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Minneapolis, MN