Carson City FreewayCarson 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 HistoryProject 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)

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

Alignment Challenges (cont.)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 1986• 18,000 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 EffortFreeway 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.)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 QualityBasin

Open Channel

Collector Channel

Detention Basinat Gravel Pit

Collector Channel

Multi-Cell RCB

Multi-Cell RCB

Single-Cell RCB

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

Significant event in Eagle Valley

Over a 100-Year event on Vicee Canyon

Major sediment loads

1997 Flood, continued1997 Flood, continued

Could have been worse – Existing gravel pit on Vicee

acted as retention basin– Roughly __ feet of sediment deposition

Inter-Local AgreementInter-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 Carson City Stormwater Master PlanStormwater Master Plan

1994 Master Plan

401b Alternatives Analysis

Northwest Alternatives Analysis

Northwest Alternatives StudyNorthwest Alternatives Study

Watershed Area for Phase 1B

Existing Detention – Within Silver Oaks Development (Evaluation)

Detention and Conveyance Alternatives

Watershed Map

Contributing Drainage AreaContributing Drainage Area

Northwest Alternatives StudyNorthwest 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 StudyNorthwest Alternatives Study

State/Local/Private Partnership– Nevada Department of Transportation– Carson City– Developers

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

Project FeaturesProject Features

Detention Basins– Shenandoah Heights (Carson City)– Eagle Canyon– Silver Oaks (3 Basins with Golf Course)

Conveyance Facilities– Channels– Culverts– Storm Drains

Project FeaturesProject Features

Pre-Project Flood Limits

Post-Project Flood Limits

Project BenefitsProject 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 DamagesErosion and Sediment Damages

Erosion and Sediment DamagesErosion and Sediment Damages

ConclusionsConclusions

State/Local Partnerships Have Benefits

WIN - WIN For Everyone

Advanced Planning Is Valuable

Everyone Saves $$$

Maintenance is Reduced

Results in Significant Public Benefits