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Design Activities

Project Overview

Design work for the Hoover Dam Bypass Project began in August 2001. The earlier studies and environmental evaluations had identified the Sugarloaf Mountain Roadway Alignment as the preferred alternative.  The new roadway alignment begins near the Hacienda Hotel and Casino on the Nevada side and follows a route just south of existing U.S. 93 to the Reclamation warehouse area. This alignment new alignment crosses over the existing roadway in a northeast direction, curves back around to the southeast and crosses back over to the south side of the existing roadway. The new alignment then proceeds in a southeast direction and cross the Colorado River approximately 1,500 feet downstream of the Hoover Dam. The new highway then proceeds past Sugarloaf Mountain and ties into existing U.S. 93 at about milepost 1.7 in Arizona. Construction of the bypass includes canyon crossing bridges, grade separation structures, wildlife crossings and the Colorado River crossing.  Several power line towers have also been relocated to make way for the new highway.

Now that the Bypass is completed the existing highway will remain in service but will not carry US 93 through traffic.  The existing roadway will continue to provide access to the dam and the Bureau of Reclamation facilities.  Also, the existing roadway will be needed to provide access for tourists visiting the Dam facilities.  The design team has provided visitor facilities, which will accommodate vehicular traffic, parking and pedestrian activities, both at the dam site and at the new bridge.

Concept Refinement/Preliminary Design Complete

The design team completed the process of refining the proposed alignment and preparing the preliminary roadway design.  The purpose of the concept refinement was to:

  • reduce construction costs while optimizing safety of the completed structure,

  • define a credible budget within the project funding limitations,

  • meet or exceed the environmental mitigation elements as described in the ROD/FEIS,

  • define a firm schedule for project delivery.

Rock Cut at Sugarloaf Mountain

Additionally the design team completed survey and mapping, geotechnical investigations, site specific seismic assessment, site specific wind loading assessment, consultation with land management agencies and natural resource agencies, consultation with Native American tribal representatives through government-to-government meetings and bridge type studies.  (Read about the results of the River Bridge Type Study below.) 

The project delivery team set a goal of reducing project impacts by improving upon the Phase B alignment. Through this process, many concept improvements were identified and implemented. The refined alignment greatly reduceds construction staging impacts, forgoes taking the BOR warehouse, eliminates the relocation of the BOR sewage treatment ponds, reduces the number of power transmission lines to be relocated, and generally minimizes the impacts of the roadway on the historic project site.

Additionally, in response to public comment during the EIS process, the design team was charged with implementing practical solutions to enhance visitor experiences and provide unique viewing opportunities of the Hoover Dam.  The final design includes a parking lot, a trail to the new bridge, a pedestrian plaza and a sidewalk on the bridge.  

View the proposed alignment here.

Or download a video animation of the proposed alignment here.
(Note: This animation is a 2.5 Meg file and will take several minutes to download without a DSL connection.)   

Colorado River Bridge Type Study Completed

 

A major project milestone was reached with the selection of the bridge type for the Colorado River Crossing. 

The type study for the Colorado River Bridge was developed by the Design Team comprised of CFLHD and the design consultant, and was guided by direction from the Federal Highway Administration, the Arizona Department of Transportation, the Nevada Department of Transportation, the Bureau of Reclamation, the National Park Service and the Western Area Power Administration.  Additionally the public had the opportunity to comment through this web site and by casting ballots at the visitor center at the Hoover Dam. Read about the preliminary design process here.

Public Input on Bridge Types

The type study considered deck arch solutions as recommended in the initial screening process.  The Type Study was completed and the Executive Management Committee selected a Composite Concrete Deck Arch Bridge. 

The composite solution was developed to address the specific design issues inherent to the Hoover Dam site.  It was recommended on the merits of cost, schedule, aesthetics and technical excellence.  The specific advantages of the concrete composite alternative include the following:

 

  • The concrete composite alternative blends the best of both concrete and steel, using concrete in compression for the arch, and lighter steel for the upper structure.  Concrete is used where it is most economical, and is efficiently placed using a form traveler system that is a proven construction technology for this type of work.

  • The concrete composite offers advantages for accelerated schedule, since the concrete arch can follow on an early foundation excavation contract without the wait for fabrication of arch steel.

  • The concrete composite alternative is the lowest projected cost for the favored solid rib alternatives, and the blend of concrete and steel design detail options allows the greatest flexibility to design for cost efficiency.

  • The composite distributes construction risks in terms of costs, quality control and schedule.  Concrete casting is completed in a confined form, and runs in parallel with steel fabrication.  The steel superstructure reduces the risk of delays and eliminates many quality control issues inherent with a cast-in-place concrete superstructure in the open environ over the gorge.  The composite structure utilizes concrete where it is most efficient and steel where it is most efficient.

  • The composite structure allows progress to occur in parallel on site during arch erection and in the shop for superstructure steel fabrication, with relative independence between these operations.

 

The selection of the composite alternative was influenced by a priority given to schedule, budget and compatibility with the Hoover Dam.  A design choice with the blend of steel and concrete also favors the composite as a single alternative with the greatest opportunity for cost control.  The construction schedule criteria favors the composite structure over the all cast-in-place concrete structure.

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Last Updated: 10/29/2010

 
 

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