Figure 02. Several sinkholes give the name to Pothole Valley, east of Buford, Colorado, on the North Fork of the White River. Photo credit: Colorado Geological Survey.

Collapsible Soils

Another type of ground subsidence that commonly occurs in Colorado is the settlement and ground collapse that occurs in certain types of geologically recent, unconsolidated sediments — usually referred to as soils by engineers and contractors. This group of soils those that can rapidly settle or collapse the ground are known as collapsible soils.

Collapsible soils are a major geologic hazard for land development in many locations across the state. This particular hazard manifests itself as ground settlement, which can be damaging to overlying structures if the soil problems are not mitigated or if the structure is not engineered properly. Ground settlement can cause severe damage to man-made structures such as foundations, pavements, concrete slabs, utilities, and irrigation works. Although not of the severity of damage related to swelling soils and heaving claystone bedrock, ground settlement has resulted in hundreds of millions of dollars in damage. As growth pressure increases in many places in Colorado, more areas susceptible to soil collapse are considered for development. The best illustration of this geologic hazard’s potential liability was the case of townhomes damaged by collapsing soils in a Glenwood Springs development built in the early 2000s. The court case resulted in a $12 million payment by the developer and his engineering consultants to the townhome owners.

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