I-25 Colorado Springs Metro Interstate Expansion Project (COSMIX) Colorado Springs, Colorado

Rockrimmon Constructors and Colorado Department of Transportation

The COSMIX project is a design-build project involving widening and improvements to I-25 from Colorado Street to North Academy Boulevard. The project includes 12 bridge structures some are multi-span and multi-bridge structures, numerous retaining walls, culverts and noise barriers.

The geotechnical conditions along the alignment vary from deep man-made fills to shallow highly expansive bedrock to wet alluvial sands overlying claystone bedrock with coal seams. Foundation types considered have included shallow spread footings, short drilled shafts for lateral support and deep drilled shafts for lateral support and heavy foundation loads.

Yeh and Associates was requested to provided design recommendations for the retaining wall and bridge foundations, design parameters for the walls, culverts and barriers and design drawings and specifications for several of the retaining walls. Recommendations for retaining walls have considered aesthetics and constraints for tie-back and/or reinforcement elements.

As part of our work on the project, we performed supplemental geotechnical investigations to provide the required subsurface information in areas of the project not fully covered by the CDOT investigations. The work is currently on-going and Yeh and Associates is providing construction observation and materials testing services during construction. Construction testing has included dynamic load testing of drilled shafts and cross hole seismic evaluation of the constructed shafts for defects.

Yeh’s key personnel who worked on the project included Shan-Tai Yeh as the project principal and QA/QC reviewer, Paul Macklin was the project manager and geotechnical lead for the design build. Bob LaForce was the materials manager during construction.