AZ/NV HOOVER DAM: Toll bridge studies for US93

Arizona DOT is calling bids for financial feasibility studies of a toll bridge over the Colorado River or Lake Mead for US93 near the Hoover Dam. At present US93 uses the 2-lanes on top of the dam and generates an ugly mix of tourists looking at the dam and through traffic. US93 is the major commercial corridor between AZ, NV, and UT and is designated a NAFTA route between Mexico and Canada.

A draft environmental impact statement has just been released. The project is on a fast track after years of dither.

Fast track

As many as 35k veh/day creep their way back and forwards across the dam in peak tourist times generating backups for miles on each side. The dam and its surrounds straddle the states of AZ and NV and are parts of the Lake Mead/Grand Canyon national park complex, one of the world’s premier tourist attractions.

The Fed Hwy Admin is managing a three-gov assessment of alternates. One of its documents states: “The traffic congestion caused by the inadequacy of the existing highway across the dam imposes a serious economic burden on the states of Arizona, Nevada, and Utah. Other alternative four-lane commercial routes between AZ, NV, and UT are through Calif, an additional 400km. The traffic volumes, combined with the sharp curves on US93 in the vicinity of Hoover Dam, create a potentially dangerous situation. A major catastrophe could occur, involving innocent bystanders, millions of dollars in property damage to the dam and its facilities, contamination of the waters of Lake Mead or the Colorado River, and interruption of the power and water supply for people in the Southwest. By developing an alternate crossing of the river near Hoover Dam, through-vehicle and truck traffic would be removed from the top of the dam. This new route would eliminate the problems with the existing roadway—sharp turns, narrow roadways, inadequate shoulders, poor sight distance, and low travel speeds. Ultimately, this project will:

• Remove a major bottleneck to interstate and international commerce in the West

• Replace an inadequate federally owned highway river crossing

• Significantly reduce traffic congestion and accidents on a major commercial route between Phoenix and Las Vegas

• Protect the dam, its facilities, and the waters of Lake Mead and the Colorado River from potential spills of hazardous cargo

• Enhance the visitors’ experience in the Hoover Dam area”

The Hoover dam is one of the most spectacular and productive public works of the Depression era. It was built in just 2 years, opening 1935. Containing 2.5m cub m of concrete, it soars 221m high and is 380m long at the top by 13.7m wide with 2 roadway lanes and sidewalks. It has a base 200m wide. The reservoir which supplies Las Vegas, Los Angeles and much farm land with water is 175km long and contains 28m acre-ft when full, making it the largest manmade lake in the US. Turbines generate some 2m kW of electricity and it can serve to alleviate flooding downstream. (Environmentalists want it removed!)

TEA21 provided $41m of fed-$s for the Dam Bypass Bridge project and three alternates have been identified — see map and table. Estimated cost of the project ranges between $133 and $147m, so major toll financing is needed to top up TEA21 monies. Steel arch truss bridges are the most economical at the contemplated spans and have become almost a western tradition. In our opinion the furthest southerly alternate, a decent distance downstream from the dam wall is likely to be the only acceptable one. The other two encroach too much on the dam and the lake. Both are clumsy and intrusive.

93-pike?

The whole 400km of US93 between the outskirts of Las Vegas and the Phoenix area will have to be upgraded soon to 2x2-lane motorway standard since this old 2-laner links two rapidly growing metro areas totalling over 4m pop. North on I-15 through Salt Lake City and Butte MT it forms a route into Calgary Alberta. South on I-10 and I-19 to Nogales, or through El Paso it represents a major trade route into Mexico.

US-93 in AZ would seem to be a major toll road prospect in itself since except for a section it shares with I-40, it is the only 2-lane stretch in these parts between the Canadian and Mexico borders. But there may be plenty of TEA21-$s. (Contacts Terry Haussler, FHWA 303 716 2116 haussler@road.cflhd.gov; Bill Hayden, financial ADOT 602 255 7524; good website www.hooverdambypass.org)