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
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
define a firm schedule for project delivery.
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
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.
the proposed alignment here.
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
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.
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
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.
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.
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