Project History Corridor Selection Study (1970’s)


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Carson City Freeway








Project History

  • Corridor Selection Study (1970’s)

  • Carson City Endorses alignment in 1984 (“Edmonds” alignment, though center of valley)

  • Right-of-Way acquisition begins in 1986



Alignment Challenges

  • Clean Water Act of 1980 (Section 404 - Wetland Issues)

  • “Species of Concern” - The Carson Wandering Skipper Butterfly

  • Water Quality Issues (NDEP)





Floodplain Impacts

  • Floodplain Impacts

    • Alignment is at low point in Eagle Valley (45 sq. mi. watershed, 100-Year = 10,000 cfs
    • FEMA Floodplains / Floodways
      • Published in 1986
      • 18,000 feet of alignment is in within regulatory floodplain
      • 8,000 feet of alignment is in floodway






Freeway Design Effort

  • NDOT Begins Design in 1994

  • Recognized the necessity for complimentary City and State designs

  • Carson City and NDOT begin cooperative effort for Freeway and City Master Plan Drainage Design



Freeway Design Effort (cont.)

  • NDOT / City / WRC Studies

    • Hydrologic Analysis of Eagle Valley
    • Galena Creek Watershed Comparison Study
    • Hydraulic Alternative Development Report
      • Included Offsite Detention Alternatives (but only on Public Lands)
    • 404(b)(1) Alternatives Report (minimize environmental impacts)
    • Lompa Lane Groundwater Analysis




New Years Day Flood, 1997 a.k.a. “Then It Rained”

  • Significant event in Eagle Valley

  • Over a 100-Year event on Vicee Canyon

  • Major sediment loads





1997 Flood, continued

  • Could have been worse

    • Existing gravel pit on Vicee acted as retention basin
    • Roughly __ feet of sediment deposition


Inter-Local Agreement

  • 1997 event stressed the need for major, comprehensive flood control infrastructure

  • Through a Partnering Process, Carson City and NDOT cooperate to develop a regional flood control solution



Carson City Stormwater Master Plan



Northwest Alternatives Study

  • Watershed Area for Phase 1B

  • Existing Detention

    • Within Silver Oaks Development (Evaluation)
  • Detention and Conveyance Alternatives





Contributing Drainage Area



Northwest Alternatives Study

  • Goals and Purpose:

    • Regional Flood Control Planning
    • Integration of Regional Flood Control with Freeway Project
    • Reduction in Costs for Freeway
    • Reduction In Costs for Carson City
    • Reduction in Environmental Impacts
    • Significant Reduction in Floodplain Area


Northwest Alternatives Study

  • State/Local/Private Partnership

    • Nevada Department of Transportation
    • Carson City
    • Developers
  • Advantages



Project Features

  • Detention Basins

    • Shenandoah Heights (Carson City)
    • Eagle Canyon
    • Silver Oaks (3 Basins with Golf Course)
  • Conveyance Facilities

    • Channels
    • Culverts
    • Storm Drains


Project Features







Project Benefits

  • Reduction in Floodplain/Floodways

  • Reduction in Facilities Costs

  • Reduction in Utility Relocation Cost

  • Reduced Flood Risk to Public Facilities

  • Reduced Maintenance Costs



Erosion and Sediment Damages



Erosion and Sediment Damages



Conclusions

  • State/Local Partnerships Have Benefits

  • WIN - WIN For Everyone

  • Advanced Planning Is Valuable

  • Everyone Saves $$$

  • Maintenance is Reduced

  • Results in Significant Public Benefits




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