DENVER - The Colorado Department of Transportation has picked a partnership of companies that will complete the enhancement of U.S. Highway 36 between Denver and Boulder.

Plenary Roads Denver - a partnership led by Plenary Group Inc., a privately held international infrastructure business - has been hired for the second phase of the project, which will add express lanes between 88th Avenue in Westminster and Table Mesa Drive in Boulder. As with the express lanes extending north of downtown Denver on Interstate 25, carpools, buses and solo drivers who pay a toll will be able to use the lanes.

Aurora-based Ames Construction and Denver-based Granite Construction are the Plenary partners that will build the lanes, and Denver-based HDR Engineering Inc. and Transfield Services (ASX: TSE) of Australia will be responsible for maintaining them. Goldman Sachs is the partnership's financial adviser.

Construction is expected to start later this year on Phase 2 and be completed by the end of 2015.

Phase 2 is CDOT's first public-private partnership. About two-thirds of the cost will be funded through private-sector equity and loans, said CDOT spokeswoman Mindy Crane, adding that the project's price tag has been estimated at $113 million although costs are still being negotiated.

CDOT and the High Performance Transportation Enterprise announced the selection Friday. April 5.

"We are extremely excited to have a partner on board to complete the final phase of the U.S. 36 improvements that will address the needs of this vital corridor and support continued economic growth in the area," said Mike Cheroutes, HPTE director, in a press statement. "We wouldn't be here today without the dedication and hard work by our local, state and federal stakeholders."

CDOT and HPTE will enter into a 50-year agreement with Plenary Roads Denver. Besides completing the express lanes, the partnership will rebuild two general-purpose lanes in each direction between 88th and Table Mesa, widen the highway to accommodate 12-foot-wide inside and outside shoulders, replace the bridge over Coal Creek and widen two other bridges. Bus Rapid Transit improvements will include new electronic display signage at stations and bus priority improvements at ramps. The improvements also will allow buses to operate on the shoulders of US 36 between interchanges to decrease bus travel time. Intelligent Transportation Systems will be installed for tolling, transit and traveler information as well as incident management. A separate commuter bikeway will be installed, and the Regional Transportation District station at McCaslin Boulevard will be improved.

The partnership also will operate and maintain the entire U.S. 36 corridor between I-25 and Table Mesa, as well as the I-25 express lanes between downtown Denver and U.S. 36 - including removal of snow and ice.

About two-thirds of the Phase 2 project costs are funded through private-sector equity and non-recourse debt, according to the CDOT press statement.

Phase 1 of the project already is under way. The Ames-Granite joint-venture team was named design-build contractor for the $312 million project and began construction in July. That phase, scheduled to open to the public in January 2015, includes rebuilding and widening U.S. 36 between from Federal Boulevard and 88th Street, and adding express lanes in each direction for Bus Rapid Transit, high-occupancy vehicles and tolled single-occupancy vehicles.