A complete retooling of U.S. 36 from Denver to Boulder begins this summer as the 60-year-old Boulder Turnpike is widened to accommodate those who travel by bus, car and even bicycle.

Earlier this week, the Colorado Department of Transportation picked Ames/Granite Joint Venture team as the design-build contractor for the $311 million in improvements along the stretch of highway from Federal Boulevard to 88th Street in Boulder County.

The project — which will generate nearly 3,500 construction-related jobs — will reconstruct the existing U.S. 36 pavement and widen the highway to add one express lane in each direction.

It also includes other improvements along U.S. 36 from Federal through the Interlocken Loop interchange.

This is considered the first phase of the long-awaited widening and modernizing of the 24-mile turnpike, which started as a toll road in 1952 and was considered of the largest projects of its kind in Colorado.

Officials say the eventual $450 million transformation of U.S. 36 — including a second phase from 88th Street to Table Mesa Drive in Boulder — will again rival anything else in the state, or maybe the country.

“This will turn U.S. 36 to a multi-modal, innovative corridor,” said Audrey DeBarros, executive director of the 36 Commuting Solutions, a nonprofit group aiming to reduce congestion and improving transportation along the highway.

The highway is already operating at 90 percent of its capacity, with 80,000 to 100,000 daily vehicle trips. Traffic conditions will only get worse if forecasts of a 53 percent increase in employment and a 28 percent population hike by 2035 come true.

“I can imagine that the only people shouting for joy over this project other than the people who commute on this route every day are the bus drivers who have to drive those buses during rush hour,” said Westminster Mayor Nancy McNally.

She is among a core group of mayors, city council members and county commissioners who began lobbying for U.S 36 improvements nearly 15 years ago. The highway galvanized even those on different ends of the political spectrum.

Boulder County Commissioner Will Toor, a Democrat and former Boulder mayor, says he and former Broomfield Mayor Bill Behrens, a Republican, disagreed on several issues.

“But Bill Behrens and I walked in shoulder-to-shoulder to an RTD meeting several years ago and said this is what we want for U.S. 36,” Toor said. “We just decided that if we keep arguing amongst ourselves, we won’t get anything done. So together, let’s see what we can do.”

The first phase of the project — from Federal to 88th Street — includes:

• Adding an express lane in each direction of U.S. 36, where bus rapid transit and high-occupancy vehicles can travel, free of charge. Solo drivers also will be able to use the express lane by paying a toll, the cost of which will vary by the time of day.

• Reconstructing existing pavement on U.S. 36 and widening the highway to accommodate 12-foot inside and outside shoulders.

• Replacing the Wadsworth Parkway, Wadsworth Boulevard (at West 112th Avenue) and Lowell Boulevard bridges over U.S. 36.

• Installing a separate commuter bikeway along much of the corridor.

Ames-Granite also agreed to extend the terminus of the project from Interlocken Loop west to 88th Street in Lousiville and Superior.

There will be several other improvements, including new electronic display signage at stations and bus-priority ramps and the reconstruction of bridges over U.S. 36 at Sheridan Boulevard and over the Burlington Northern Santa Fe Railway.

Funding for the first phase of the project comes from a hodgepodge of sources, including $120 million in RTD sales-tax revenue, $44 million in Denver Regional Council of Governments federal funds, a $52.9 million loan from the U.S. Department of Transportation Infrastructure Finance and Innovation Act, $46 million from the Colorado Bridge Enterprise and a $10 million grant from the American Recovery and Reinvestment Act.

“It took a lot of partnerships and a lot of funding sources to assemble a project of this size,” said DeBarros. “I think the way we handled this is the wave of the future.”

The design-build team includes Ames Construction Inc., from Burnsville, Minn., which has an office in Aurora. Granite Construction is based in Watsonville, Calif; HDR Engineering Inc., is based in Omaha; and Michael Baker Corp is from Pittsburgh. HDR Engineering and Michael Baker also have offices in the metro area.

It’s hoped the new express lanes will be open to the public by Dec. 31, 2014.

Project planners — CDOT, the Regional Transportation District and the Colorado High Performance Transportation Enterprise — want to finish the second phase of the highway improvements at roughly the same time, although funding has not been secured.

Still, Toor is looking forward to extending the improvements to Boulder. The second phase of the project is expected to begin in winter 2013.

“I’m very hopeful we’ll get those rapid- transit bus lanes here,” Toor said.

Monte Whaley: 720-929-0907 or mwhaley@denverpost.com