The COSMIX project, completed in December 2007, was the largest transport improvement project in Colorado Springs’ history.

This comprehensive $150-million design-build project rebuilt interchanges, reduced roadway curvature, improved storm drainage, mitigated roadway noise, and expanded Interstate-25 (I-25) to six full traffic lanes through northern Colorado Springs. CH2M HILL was the majority owner of the joint venture responsible for the design-build approach, which allowed work to begin on construction prior to 100 percent design completion. Benefits were gained when the design-build team found cost-saving ways to reduce lifecycle costs while enhancing the project. For example, the design shortened the storm drain system to minimize construction impacts to the historic 1930’s Work Progress Administration (WPA) wall and floodplain habitat at the Monument Valley Park. The project entailed 800,000 cubic yards (CY) of earthwork, 200,000 CY of concrete and 110,000 tons of asphalt paving. The scope of works included one major split diamond interchange including 12 bridge structures, widening of 12 miles of I-25 to six lanes, reconstruction of 16 bridges including interchanges with the Union Pacific Railroad, a wetlands mitigation programme with routine monitoring of an environmentally sensitive waterway and all whilst allowing the continuous use by 100,000 vehicles per day. Ultimately the project was completed one year ahead of planned Colorado Department of Transport (CDOT) schedule.

Key to success on the project was the way that the project was divided into four construction segments to allow concurrent design and construction of multiple elements. This was achieved by:

• An aggressive design and construction schedule that required early construction.
• Starting critical construction elements in segments 2 and 3 while design was ongoing.
• Splitting the four project segments into 14 design packages to optimize phasing.
• Designing, fabricating, and delivering long-lead materials to the project site on time.
• Conducting phased reviews of plans to allow early construction in each segment.
• Performing proposal-phase aerial photography and pre-award project mapping that provided a head start to our 18-month design phase.

Quality, safety and public information planning were fully integrated into these processes to ensure a comprehensive programme management approach. The project was delivered by a collaborative team comprising 180 staff from the joint venture and 45 staff from CDOT.

The successful approach was founded on design-build Building Information Modelling (BIM) based on Bentley software solutions. These were used to deliver the preliminary design for the initial proposals, the design deliverables driven by the construction schedule, ‘living’ plan documents and were able to integrate the efforts from multiple, and dispersed, designers providing relevant and timely electronic deliverables against a fast paced schedule.

The BIM technology (InRoads) was used to:

• Convert 7 different survey data areas, CAD/design data based on multiple software systems and 3 different centre line station bases into one complete project coordinate base and InRoads files.
• The use of Light Detection and Ranging (LIDAR) high-definition survey techniques to create 3D models of existing structures and topography which are integrated into the overall BIM model.
• Present preliminary designs, including alternative configuration concepts and the ability to quickly visualise and assess design alternatives, to CDOT.
• Develop project standard InRoads standards, file structuring and appropriate guidelines.
• Integrate the efforts of multiple designers.
• Align the design schedule with the construction schedule and provide access to the current status of plans for all members of the team through Bentley’s Digital I Plot and Digital Archive.
• Provide direct coordination of design data with field survey and construction crews ensuring accuracy and consistency as well as integrating the Quality Control systems with the BIM. Deliverables included 3D models which provided direct GPS control of plant and grading equipment.

The ability to deliver to requirement, on target for cost and one year early was based on:

• Time invested in initial planning and setup.
• Having a single BIM system to manage CAD setup and configuration and underpin the entire design and build process.
• Frequent sanity check reviews of the design process using the BIM model of the ‘living design’.
• A fully integrated team of designers, constructors, BIM support team and client.