GeotechnicalEngineering FoundationDesign SubsidenceMitigation

Geoengineering Resilience: Building a Fire Station Over an Abandoned Mine in Colorado

*The Frederick-Firestone Fire Station No. 5 in Colorado was built over an abandoned coal mine. Source: Structures Magazine*

The Frederick-Firestone Fire Station No. 5 in Colorado stands as a remarkable case study in geoengineering. Constructed over an abandoned coal mine, the project faced significant subsidence risks—a challenge that required advanced geotechnical solutions to ensure safety and longevity. Through an innovative floating foundation, modular structural design, and strategic material selection, engineers have successfully built a resilient fire station capable of withstanding future ground movement.

Mitigating Subsidence Risks with Smart Geoengineering

Building atop a historically mined site presents unpredictable ground conditions due to subsurface voids left behind by room-and-pillar mining. These voids increase the risk of differential settlement, ground collapse, or structural damage. To counter these hazards, engineers implemented proactive geotechnical measures:

Segmented Structural Design: Instead of a single, rigid structure, the fire station comprises three independent buildings, minimizing the impact of uneven settlement.
Shallow Raft Foundation: A floating foundation was chosen to allow the structure to adapt to minor ground shifts, reducing stress on critical load-bearing elements.
Flexible Material Selection: Cold-formed steel (CFS) infill walls provide ductility and seismic resilience, while a concrete masonry veneer ensures durability and impact resistance in high-use areas.

By incorporating these elements, the design allows for controlled deformation, ensuring that minor subsidence does not compromise the station's operational integrity.

Segmented structure: Instead of a single large building, the station consists of three separate structures, reducing stress from uneven subsidence. Source: Structures Magazine

Innovative Structural Engineering for Long-Term Stability

Beyond the foundation, the superstructure was engineered for adaptability. Steel moment frames were incorporated to provide both seismic resistance and flexibility, allowing the building to adjust to potential settlement over time. Key structural innovations include:

Expansion joints between structures to allow for controlled, independent movement.
Flexible utility connections designed to withstand ground shifts without damage.
Controlled veneer cracking to accommodate minor deformations while maintaining structural integrity.
Deep reinforcement within the raft foundation to distribute structural loads efficiently.

These geotechnical strategies ensure that even in a worst-case subsidence event, the fire station remains operational—a critical factor for emergency response infrastructure.

A Model for Building in Challenging Geological Conditions

The Frederick-Firestone Fire Station No. 5 is more than just a firehouse—it is a benchmark for resilient construction on geotechnically challenging sites. By combining modern geoengineering techniques with adaptive foundation and structural solutions, this project sets a precedent for future developments in subsidence-prone areas.

As urban expansion continues into areas with historic mining activity, this station serves as proof that geotechnical foresight and innovation can overcome even the most unpredictable terrain challenges.

Source: structuremag.org