Carson City Freeway Paul M. Frost, P.E. Principal Hydraulic Engineer Nevada Department of Transportation Mark E. Forest, P.E. Executive Vice-President WRC Nevada, Inc. Mahmood Azad, P.E. Development Services Manager Carson City

Carson Freeway Phase I - Red Phase II - Blue

Phase I - Carson 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 Wetland Issues) “Species of Concern” - The Carson Wandering Skipper Butterfly Water Quality Issues (NDEP)

“Thank you for visiting Carson City” Nevada Appeal, 1999

Alignment Challenges (cont.) Floodplain Impacts –Alignment is at low point in Eagle Valley (45 sq. mi. watershed, 100-Year = 10,000 cfs –FEMA Floodplains / Floodways Published in ,000 feet of alignment is in within regulatory floodplain 8,000 feet of alignment is in floodway

Floodway 100-Year Floodplain Zone B (Shallow) Carson Freeway

Floodway 100-Year Floodplain Zone B (Shallow) Carson Freeway

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

Water Quality Basin Open Channel Collector Channel Detention Basin at Gravel Pit Collector Channel Multi-Cell RCB Single-Cell RCB

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 1994 Master Plan 401b Alternatives Analysis Northwest Alternatives Analysis

Northwest Alternatives Study Watershed Area for Phase 1B Existing Detention –Within Silver Oaks Development (Evaluation) Detention and Conveyance Alternatives

Watershed Map

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 –Land Acquisition –Shared Costs –Regional Flood Control Measures Expedited

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

Pre-Project Flood Limits

Post-Project Flood Limits

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

Conclusions State/Local Partnerships Have Benefits WIN - WIN For Everyone Advanced Planning Is Valuable Everyone Saves $$$ Maintenance is Reduced Results in Significant Public Benefits