Construction of the largest concrete arch in North America, a key part of the Hoover Dam bypass, is within about six feet of completion, a U.S. spokesman said.

The Federal Highway Administration showed off the 85 percent complete portion of the $114 million bridge at a media briefing Friday. The arch is the centerpiece of the bypass project, which will carry traffic on U.S. 93 between Arizona and Nevada without crossing the Hoover Dam.

The project should be finished by the end of 2010, project manager Dave Zanetell told the Las Vegas Sun.

Zanetell said after the arch is connected in two to three weeks, crews will work through September to remove equipment and temporary support towers and cable systems. Once the cables are removed and the arch is free standing, it will take about 11 months to complete the bridge.

The bridge will be 1,900 feet long. It is 1,700 feet downstream from the dam and 890 feet above the Colorado River.