Looking southwest from US 36, the 120th Avenue Connection will cross this field.

The Colorado Department of Transportation, Broomfield and the Federal Highway Administration are funding the $23 million design-build project that is being handled by a team headed by Edward Kraemer & Sons and HNTB. The construction period is about 18 months.

The parties are holding a groundbreaking ceremony Thursday morning at the site.

The traffic problem exists there primarily because the Boulder Turnpike, which is U.S. 36, cuts diagonally right through the area where Wadsworth Parkway on the south, CO 128 on the west, U.S. 287 on the north and 120th Avenue on the east converge. You can read about the history of the Boulder Turnpike here.

It forces all sorts of maneuvers that traffic engineers call “out of direction turns,” through which drivers have to zig-zag out of their direction of travel in order to keep going the way they were headed.

The problem is made worse by growth in traffic over the years that overwhelms the road network.

The first part of the 120th Avenue Connection project will design and build the new roadway, in red, and the local streets running north-south, in dark blue. A later phase will complete the tie-in to 120th Avenue on the east, in light blue on the right.

This initial phase of construction will build the major elements, including a new bridge curving over the turnpike about four-tenths of a mile southeast of the Wadsworth Parkway bridge. It will allow east-west traffic to bypass the worst of the congestion.

But this first phase won’t complete the roadway connection on the east side. Because the new curving roadway must bridge over the Burlington Northern Santa Fe Railway tracks, cut a swath through some developed private properties and require extensive realignment of the current local streets including turning some into cul-de-sacs, neither CDOT nor Broomfield has the estimated additional $40 million this later phase will cost. Much of that cost will be for acquiring the right-of-way.

In that later phase, the connection would be made to existing 10th Avenue at Teller Street. That would give the complete new roadway a length of about 1.2 miles.

It’s a lesson in how sometimes, the funding situation in transportation forces agencies into breaking up projects into segments that can stand alone and provide some relief to safety, mobility or other issues without yet completing the whole project. Building serviceable segments in stages when they can be paid for makes sense, while planning for funding for the remainder.

But for now, traffic on the east will connect to 120th by turning onto an extended Commerce Street.

You can read here the 2005 Environmental Assessment document that studied the project and other alternatives.

Design-build is a method of project delivery that combines final design with the construction process, taking the owner’s performance requirements and allowing the contracting team the ability to achieve potential cost and schedule savings by blending the design-construction process in real time.

This was the process used by CDOT and RTD on the successful T-REX highway and transit project on Interstates 25 and 225, which was completed in 2006. CDOT is using it for several other multi-faceted road projects, and RTD intends to use in to try to cut costs on its remaining FasTracks transit corridors.