136th Ave. and I-25 Interchange

Submitted by SEMA Construction Inc.

The new interchange at 136th Avenue and Interstate 25 will provide much needed access to the North Denver area and was designed to alleviate traffic congestion at 120th Avenue and I-25.

This highly visible project consisted of new exit ramps at 136th Avenue, an extension of 136th Avenue, new bridges over I-25 and Big Dry Creek and intersection improvements at Huron and Washington streets. Two underground pedestrian crossings were built on each side of I-25 for future development.

The unique use of 12,700 sq ft of Colorado native stone landscape walls and extensive landscaping highlight this new gateway to the cities of Westminster and Thornton.

Construction challenges encountered during this project were threefold. First, to attain the desired strength, the landscaped walls were designed with stone masonry and incorporated an MSE grid system, thus keeping the stone wall appearance.

Secondly, the ornamental pedestrian bridge rail was designed with a steel truss system attached to the railing. This low-tolerance system mandated the installation of several embed bolts and plates, installed with precise field quality control. The integrated rail and truss systems connected not only to each other, but also to the other bridge components. Additionally, most of this work had to be done over I-25 at night with lane closures.

Finally, a red-tailed hawk was found nesting within the project limits at the start of construction, placing the project on hold for two months. With over 225,000 cu yds of embankment to be placed in this area, diligent scheduling of labor and equipment was required to keep the project on track.

Through the combined efforts of the city of Westminster, the city of Thornton, Felsburg Holt & Ullevig and SEMA's team, the envisioned preconstruction concepts were delivered before the project's grand opening on July 21.

Project Team

Owners: the city of Thornton and the city of Westminster
Designer: Felsburg Holt & Ullevig
General Contractor: SEMA Construction Inc.
Major Subcontractors: DKS Enterprises, Premier Paving and Aquatic & Wetland Co.

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