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US 550 South Connection

Durango, Colorado

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This $75 million project consists of 5.6 miles of new and reconstructed fout-lane roadway, including replacing a steep, narrow, curvy section of US 550 with a smooth, wide, four-lane roadway and a connection to the US 550/US 160 Interchange.
Our team was hired to take a fresh look at the US 550 project because the NEPA process had been at a stalemate for many years and had received numerous challenges from a ranch owner. CDOT maintained that a slight variation of the original Selected Alternative was still the Preferred Alternative, while the ranch owner’s engineering and legal team insisted that another solution along the existing alignment better met the Section 4(f) requirements.
Unable to break the stalemate, CDOT hired a team led by Wood and Muller to perform an Independent Alternatives Analysis. Our team was provided all previous studies and given free reign to do whatever we felt necessary to determine the best location for US 550.
To bring objectivity to the analysis, the Muller/Wood team stepped back to the fundamentals. We performed a detailed analysis of the US 550 corridor and site characteristics to determine the appropriate design speeds in the project area. Using new traffic projections created by a corresponding independent traffic projection study, we conducted traffic safety and traffic operations analyses.
The key to success was the stakeholder involvement program. The team embarked on a mission to meet with all key stakeholders to understand their needs and desires associated with the highway. We held both individual meetings and group meetings to identify common ground. We developed a new potential alignment in an attempt to meet the needs and desires of all stakeholders, and, at the same time, satisfy the requirements of the two driving NEPA requirements: Section 4(f) and the Clean Water Act.
A thorough evaluation was conducted of the impacts resulting from the ranch owner’s alignment, CDOT’s Supplemental EIS Preferred Alternative, and the Muller/Wood alignment. That evaluation determined that the Muller/Wood alignment best met the requirements of Section 4(f) and was also the Least Environmentally Damaging Practicable Alternative under the Clean Water Act.
A key element of the project was the introduction of a roundabout not previously part of the NEPA preferred alternative. The rugged terrain of the Florida Mesa created unique design challenges as the roundabout is situated adjacent to an existing bridge abutment, tucked into the edge of the mesa on a downhill retaining wall, and required 130-foot-deep cuts. At subsequent group meetings in late 2014, all key stakeholders, including the ranch owner, expressed their approval and support for the Muller/Wood alignment. As a result of the Independent Alternatives Analysis, CDOT and FHWA have updated the Supplemental EIS/Section 4(f) Evaluation, and a new ROD was signed on May 15, 2015.
Muller was a subconsultant to provide CDOT with design-build reference documents for procurement phase of the project. Muller’s responsibility was developing the conceptual and preliminary roadway design for the northern 1.5 miles, and drainage design for the entire corridor. We also led preparation of several chapters of the design-build reference documents, served on CDOT’s project leadership team, and are remaining on the team as owner’s representative for the related construction.


CDOT Region 5


Transportation Planning & Design
Traffic Engineering & ITS
Stormwater & Floodplain Management


2.6 Miles of Rural Roadway Miles | 1 Intersection | 1 Roundabout  

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