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Stabilizing Colorado’s Highway 119 with SignatureStone Gravity Walls​

Project Overview

  • Location: Colorado State Highway 119 (Between Boulder and Nederland)

  • Engineers: Yeh and Associates; Ground Engineering

  • Wall Type: Gravity Walls

  • Total Wall Face: 11,500 sq. ft (approx. 1,070 sq. meters)

  • Maximum Height: 18.5 ft (5.6 meters)

The Challenge:

The Colorado Department of Transportation (CDOT) faced a significant engineering hurdle on Highway 119—a critical link between Boulder and Nederland. To improve safety and road geometry, the highway required widening in a steep, mountainous canyon.

Traditional construction methods were complicated by several factors:

  • Tight Footprint: The narrow canyon provided very little room for excavation or massive reinforcement zones.

  • Environmental Sensitivity: The project needed to minimize the impact on the surrounding natural landscape.

  • Traffic Flow: Because this is a high-traffic mountain pass, the solution needed to allow for efficient installation to minimize road closures.

The Solution:

Working in conjunction with Yeh and Associates and Ground Engineering, a gravity wall system was selected as the optimal solution. This approach eliminated the need for geogrid or extensive tie-backs, which would have required significantly more excavation into the mountain.

Key technical aspects of the solution included:

  • Utilization of Massive Blocks: The project utilized large-scale precast blocks to provide the necessary mass for stability.

  • Optimized Wall Design: Dr. Sean Chiang and the engineering team designed several wall segments, including a primary wall reaching heights of up to 18.5 feet.

  • Aggregate Infill: To handle the specific drainage needs of the canyon environment, a 3/4-inch angular aggregate was used for infill.

The Installation:

The installation process was streamlined to meet the project’s demanding schedule:

  • Efficient Staging: Blocks were delivered and staged to allow for continuous installation.

  • Speed of Construction: By using a gravity system, the crew was able to install the blocks rapidly without waiting for the time-consuming process of geogrid placement and compaction.

  • Tight Tolerances: The system successfully navigated the curves and elevation changes inherent in the canyon highway.

The Outcome:

The project was completed successfully, providing the structural integrity needed to widen Highway 119 while maintaining the aesthetic harmony of the canyon.

  • Structural Success: Over 11,500 square feet of wall face now provide long-term stabilization for the highway.

  • Safety Improvements: The widened road allows for safer travel for thousands of commuters and tourists daily.

  • Professional Recognition: The project stands as a benchmark for using gravity wall systems in challenging, high-altitude environments.

“We used a massive amount of backfill on this, 3/4-inch angular stone, as well as interesting things like switching from fill to and an coarser aggregate backfill, working with the Redi-rock blocks, and complicated wall over-lay requirements.” — Don Dodge, Flatiron Construction

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