SubsidenceMitigation GeotechnicalEngineering StructuralInnovation CoalMine

Innovative Foundations in Colorado: How Engineers Designed a Fire Station Over an Abandoned Mine

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

The construction of Frederick-Firestone Fire Station No. 5 in Colorado is a remarkable feat of geotechnical and structural engineering. Built over an abandoned coal mine, the project faced significant subsidence risks that required innovative engineering solutions. From a floating foundation to a modular structural design, the fire station is a testament to modern engineering resilience and adaptability.

Mitigating Subsidence Risks with Advanced Engineering

The site's history as a coal mining hub posed a serious challenge, as subsurface voids left by the mining process increased the risk of ground subsidence. The engineering team had to anticipate potential ground shifts and design a structure capable of withstanding future ground movement.

To address these concerns, the design incorporated:

A segmented structure: Instead of a single large building, the station consists of three separate structures, reducing stress from uneven subsidence.
A shallow raft foundation: This foundation system "floats" on the soil, providing flexibility to absorb minor shifts without causing structural damage.
Strategic material selection: Cold-formed steel (CFS) infill wall framing was used for its ductility and resilience, paired with concrete masonry veneer for durability and impact resistance.

These measures ensured that the station remains operational even if the ground beneath it continues to settle.

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 Solutions for Safety and Longevity

The superstructure was designed to be both durable and flexible. Steel moment frames were implemented to provide seismic resistance while accommodating potential subsidence-related movements. Additionally, expansion joints were strategically placed to allow independent movement between different sections of the building.

To further enhance resilience:

Utility connections were designed to be flexible, allowing movement without causing damage.
Controlled veneer cracking was integrated into the design to allow for minor deformations without compromising the building’s integrity.
Deep reinforcement in the foundation was included to distribute structural loads effectively.

Through these methods, the fire station achieves both safety and longevity, ensuring reliable emergency response services for decades to come.

A Modern Fire Station Built to Withstand Geological Challenges

Despite the geotechnical hurdles, Fire Station No. 5 was successfully designed to meet the growing demands of Frederick and Firestone’s expanding communities. By integrating cutting-edge engineering principles, the project provides a blueprint for building on challenging terrains, proving that strategic engineering can overcome even the toughest environmental constraints.

Source: structuremag.org