Geologists begin mapping work for dam bypass

Geologic mapping and geotechnical assessment by AMEC's Earth and Environmental operations have begun for the Hoover Dam bypass project.

The four-lane divided highway and 1,900-foot bridge will bypass the heavily congested U.S.

Highway 93 road across the dam.

AMEC's Phoenix office belongs to the consulting group selected for the project by the Federal Highway Administration.

HDR Engineering leads a group of 19 companies that will provide comprehensive engineering and architectural design services for the $198 million project.

Since Sept.

11 terrorist attacks on the East Coast, trucks, RVs and trailers have been banned from the dam crossing.

Vehicles are checked on each side to avoid any danger to the dam.

The trucks are diverted onto State Route 68 through Laughlin where the cross the Colorado River.

The Arizona Department of Transportation has taken steps to make the steep grades of Route 68 safe for the truck traffic that crossed Hoover Dam prior to Sept.

11.

The 6 percent grades require trucks to use brakes and slow on the downhill runs.

Regular truck inspections are being conducted and drivers advised of the steep grades.

Hoover Dam has been the main vehicle crossing of the Colorado River since the dam was constructed in the 1930s.

The first task for AMEC is geologic mapping of the bypass route about 1,500 feet downstream from Hoover Dam and 840 feet above the river.

Laser and visual inspection of the geologic and seismic evaluation of the canyon site, will map the area.

AMEC staff will rappel down the vertical Black Canyon walls reminding engineers of the methods used when Hoover Dam was constructed.

Hoover Dam was designated one of the marvels of engineering constructed in last 2000 years by the American Society of Civil Engineers.

"Our geologists have years of experience and probably were not as active rappelling as shown in the videos of Hoover Dam construction," AMEC Communications Manager said.

In addition to the main bridge, the 3.5-mile project will include approach bridges, a tunnel in Nevada, interchanges with current highways and several wildlife structures.

Preliminary design work will follow the geologic work with construction to begin late in 2002.

"Construction will take about five years and is anticipated to be completed in 2007," Dave Zantetell said.

He is the project manager for the Central Federal Lands Highway Division out of Denver.

He said the final design will be chosen after all the various groups involved have reviewed the options.

Hoover Dam is a National Historic Landmark and the selection of design will minimize adverse effects on the dam.

The bypass will relieve the congestion on the major route from Mexico through Arizona to Canada and take the traffic back off Route 68.

Hoover Dam will remain open to the public throughout construction although restrictions brought on by the Sept.

11 events have limited travel.

ADOT Kingman District Engineer Debra Brisk said Arizona would be responsible for construction of the roadway from the bridge to the end of the Lake Mead National Recreational Area.

ADOT has not begun design and the construction is not yet in the ADOT five-year plan.