Large transportation infrastructure projects led the list of top starts in the Mountain States region for 2014, as Denver and Salt Lake City officials are working to meet the needs of a fast-growing population in both metro areas.

Salt Lake International Airport's $1.5-billion Terminal Redevelopment Program topped the list. The TRP is building 4 million sq ft of new facilities at the airport, including a new terminal and concourse and a connecting parking deck. The project also will improve and rehabilitate other structures, roadways and overpasses. Construction is being led by a joint venture of Holder and Big-D Construction. Completion is expected in 2023.

In Denver, the Regional Transportation District is pushing ahead with work on its massive FasTracks transit program, which entails 122 miles of new commuter rail across the metro area. The FasTracks plan includes the 2014 start of the North Metro Rail Line. The $343-million project, being built by Regional Rail Partners, will run between Union Station in downtown Denver and 124th Avenue to the north. It is scheduled for completion in 2018.

Other transportation projects of note that started last year include the $98-million U.S. 6 Bridges design-build project, which aims to improve mobility through the Interstate 25/U.S. 6 interchange in west Denver. Contractor Edward Kraemer and Sons Inc. is replacing six older bridges with six new ones, adding new ramp structures and a bike and pedestrian bridge over U.S. 6 to connect Barnum Park North with Barnum Park South. The project will finish this fall.

The Colorado Dept. of Transportation has launched several initiatives to ease congestion, especially weekend traffic snarls, in the I-70 mountain corridor from Denver to Silverthorne. The Eastbound I-70 Peak Period Shoulder Lane project in Clear Creek County, led by Mountain Corridor Constructors, started in May. It is widening eastbound I-70 between Empire and Idaho Springs to create a third tolled express lane on the shoulder that will be used only during peak travel times. The $72-million project also will replace bridges over I-70 at exits 240 and 241 and construct retaining walls.

CDOT started a companion project in April 2014 to reduce traffic jams through the same I-70 corridor near Idaho Springs. The Kraemer/Obayashi JV team is widening the westbound side of the Veterans Memorial Tunnels to 53 ft, which will eventually accommodate a third lane along westbound I-70. Widening of the eastbound tunnel was completed last year.

The Utah Dept. of Transportation is extending the longest continuous express lanes in the country with the reconstruction of I-15 through Davis County. The $117-million project also replaces several bridges from North Salt Lake to Farmington and creates new interchange configurations at 2600 South and 500 South. Contractor WW Clyde & Co. will complete construction later this year.

UDOT is also reconstructing a seven-mile section of I-80 from Silver Creek to Wanship in Summit County, one of the most heavily traveled highways in Utah, using new concrete pavement. The $43-million project replaces the westbound bridge over Silver Creek. Contractor Geneva Rock will finish this fall.

The Idaho Transportation Dept. is replacing the I-84 Meridian Road Interchange and improving the interstate between Meridian and Five Mile roads. Concrete Placing Co. of Boise is leading the $50.8-million project.

Several education projects also made this year's list, including a $156-million expansion of the University of Colorado's Athletics Complex, the largest design-build sports project ever for Mortenson Construction. The work includes a 200,000-sq-ft expansion of CU's Folsom Field in Boulder; a 120,000-sq-ft, net-zero energy indoor practice facility; and a 550-stall parking garage.

Other education facilities that got underway in 2014: a $95.7-million renovation of Natrona County High School in Casper, Wyo.; the new $86.1-million Laramie High School in Laramie, Wyo.; CU Boulder's $66-million Sustainable Energy and Environment Complex; a new $56-million high school in Lehi, Utah; and the $56.7-million Weber State University Tracy Hall Science Center in Ogden, Utah, which includes 165,00 sq ft of teaching laboratories, research laboratories and classrooms.

Office, commercial and hospitality projects also made the list. PCL Construction's $89-million STRATA-Vail will replace the Lionshead Inn and Lionshead Inn Annex Hotels with new mixed-use space that includes 80 for-sale luxury condos. The $72.9-million CoBank Center in Greenwood Village, Colo., is an 11-story, build-to-suit office complex being built by Adolfson & Peterson Construction. GE Johnson is building 100 Saint Paul, an 8-story Class A office tower and three levels of below grade parking in Denver's high-profile Cherry Creek North neighborhood.