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CSAH 112 Long Lake

CH 112, formerly STH 12, was originally constructed as part of the Minnesota’s trunk highway system. In the mid to late 2000s, MnDOT built the STH 12 bypass and returned jurisdiction of old STH 12 (Current CH 112/Wayzata Boulevard) to Hennepin County. The roadway was primarily designed for efficient traffic movement through the corridor and did not adequately address many local priorities such as pedestrian mobility and safety, parking, bicycle trail connectivity, and access.

Hennepin County retained SRF and Gale-Tec to provide design services for the four-mile-long corridor, including roadway and trail design, water resources design, traffic analysis, environmental documentation and permitting, right of way services, cost opinions, construction plans and bid documents.

Along with the standard storm sewer and culvert crossing design, the project had two unique water resources and geotechnical design elements:

  • Lake shore stabilization and Reinforce Soil Slope (RSS) wall design
  • Long Lake Creek Realignment

CH 112 runs adjacent to Long Lake for approximately 1,400 feet. The existing roadbed was undermined by wave action and erosion of poor soils. SRF performed wave run-up analysis and design revetment protection to integrate with the RSS wall design by Gale-Tec. The RSS wall allowed for removal of poor soils and reinforcement of the roadbed with geosynthetics layered in the lifts.

The road and trail improvements also required Long Lake Creek, the outlet of Long Lake, to be realigned over approximately 300 feet. The channel runs along the road embankment and weaves between a steep slope and homes. Design elements for the channel included a mix of bioengineering with live staking, geosynthetics, and hard armoring. Hydraulic modeling determined velocities at critical locations in support of shear stress calculations. This allowed for a refined design that provided a balance between stabilization and aesthetics.

Construction sequencing and maintenance of traffic within a narrow and confined corridor required staging to be a major focus and dictated the practical sequencing of some of the unique features of the project.

SRF continued our role on the project by assisting the County during the construction phase. Our role included providing shop drawing review, design support, and construction observation.

Hennepin County
Long Lake, Minnesota
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