Quick answer: According to the Colorado Geological Survey, expansive soil is the most significant geologic hazard in Colorado, causing more property damage statewide than floods, earthquakes, and tornadoes combined. Colorado Springs sits directly on some of the Front Range’s most problematic clay formations, primarily the Pierre Shale and adjacent claystone units.

A volume increase of just 3% or more is generally considered potentially damaging to a structure, and CGS puts swell pressures in these formations as high as 30,000 pounds per square foot. Site development here has to plan around that reality from the start, not react to it after a foundation cracks.

Why This Region Specifically

Colorado Springs sits at the transition zone between the Pikes Peak massif and the high plains, which produces a genuinely varied soil profile across a single metro area: granular alluvial deposits along Fountain Creek, weathered granite colluvium near the foothills, and, across large portions of the developed area, expansive claystone tied to the Pierre Shale formation.

That Pierre Shale connection isn’t unique to Colorado Springs. It runs the length of Colorado’s Front Range corridor, through Denver Metro, Colorado Springs, and Pueblo, and it’s specifically why this region shows up repeatedly in state and federal geologic hazard research on expansive soils. The Colorado Geological Survey has published research specifically on this city’s risk pattern: MS-32, “Map of Areas Susceptible to Differential Heave in Expansive, Steeply Dipping Bedrock, City of Colorado Springs”, which maps where this specific hazard concentrates within city limits.

The Scale of the Problem, in Real Numbers

The Colorado Geological Survey’s own hazard assessment puts the scope in perspective:

• Expansive soils cause more damage nationally each year than floods, hurricanes, tornadoes, and earthquakes combined
• One in five Coloradans is affected by expansive soil damage over time, compared to one in ten affected by flooding
• Of new homes built on expansive soils, roughly 60% see only minor damage, but 10% see significant damage, some of it beyond repair
• A volume increase of 3% or more is generally considered potentially damaging and requires a specifically engineered foundation response

The clay minerals responsible, primarily smectite (including montmorillonite) and bentonite, are what make Pierre Shale and related formations behave so differently from ordinary soil. These minerals absorb water into their molecular structure and expand, then release it and shrink as conditions dry out, and that swell-shrink cycle repeats every time moisture conditions change seasonally.

What Swelling Clay Actually Does to a Site

The mechanism is straightforward, even if the consequences aren’t: when these clay minerals get wet, they expand, sometimes by 20% or more in volume, exerting pressures the Colorado Geological Survey puts at 20,000 pounds per square foot or greater, up to as much as 30,000 psf. When conditions dry out, the same soil shrinks, pulling away from whatever it was pushing against.

That cycle, repeated over years, is what produces:

• Cracked foundation walls and slabs
• Differential movement across a structure’s footprint, since swelling rarely happens evenly across a site
• Buckled pavement and cracked concrete flatwork
• Ruptured underground utility lines, where rigid pipe can’t accommodate the ground movement around it
• Damage to bridge approaches and other civil infrastructure where differential settlement affects the transition between structure and ground

Why This Matters More for Some Structures Than Others

Not every structure on expansive soil experiences the same risk. Heavily loaded structures with deep, well-engineered foundations, downtown high-rises, for example, generally carry enough weight and foundation depth that expansive soil movement doesn’t produce meaningful damage.

The structures most at risk are lightly loaded ones with shallow, minimally engineered foundations: single-family homes, and public buildings like schools built on constrained budgets. That’s a direct function of load and foundation design, not luck, and it’s part of why site-specific geotechnical evaluation matters more here than in a region without this hazard.

How This Shapes Grading and Site Development

Expansive soil conditions change how a site gets developed well before a foundation is ever poured:

• Moisture control during and after construction becomes a central design consideration, not an afterthought, since uncontrolled moisture change is what actually triggers swell and shrink cycles
• Grading and drainage design has to actively direct water away from foundations and slabs rather than allowing it to pond or infiltrate near structures
• Foundation type selection on known expansive soil sites often shifts toward deeper, more heavily engineered systems designed to resist or accommodate soil movement, informed by site-specific swell testing
• Utility trenching requires backfill and bedding practices that account for the same seasonal ground movement affecting the soil around the structure

The standard testing methods used to characterize this risk on a specific site are the consolidation swell test, used for building foundation design, and the California Bearing Ratio (CBR) swell test, used for road and pavement design. Both require site-specific soil sampling, since swell potential varies meaningfully even across a single development, depending on which clay units are present at a given location and depth.

What This Means for Planning a Colorado Springs Project

Given how variable expansive soil conditions can be even within a single site, a geotechnical investigation early in project planning isn’t a formality here. It’s the difference between a grading and foundation plan built around actual site conditions and one built around an assumption that turns out to be wrong once excavation starts.

For civil construction and site development work specifically, that means grading design, drainage planning, and utility installation all need to be coordinated with what the geotechnical data actually shows for that parcel, not a generic regional assumption about “Colorado Springs soil.” This is a routine part of how 633 Construction approaches grading design on Front Range sites, coordinating drainage and moisture control with the actual soil conditions found on each parcel rather than a citywide assumption.

Key Takeaways

• The Colorado Geological Survey identifies expansive soil as Colorado’s most significant geologic hazard, causing more damage than floods, earthquakes, and tornadoes combined.
• Colorado Springs sits on Pierre Shale and related claystone formations that run the length of the Front Range corridor.
• A volume increase of 3% or more is generally considered potentially damaging; CGS puts swell pressures in these formations as high as 30,000 pounds per square foot.
• Lightly loaded, shallow-foundation structures (homes, budget-constrained public buildings) carry the most risk; heavily loaded, deep-foundation structures carry the least.
• Site-specific geotechnical testing, not general regional assumptions, should drive grading, drainage, and foundation decisions on any Colorado Springs site.

FAQ

Why is expansive soil such a significant issue in Colorado Springs specifically?

Colorado Springs sits on Pierre Shale and related claystone formations that run the length of Colorado’s Front Range, containing clay minerals like smectite and bentonite that swell significantly when wet and shrink when dry.

How much can expansive soil actually move a structure?

A volume increase of 3% or more is generally considered potentially damaging, and the Colorado Geological Survey puts swell pressures in Front Range clay formations as high as 30,000 pounds per square foot.

Does expansive soil affect every building the same way?

No. Heavily loaded structures with deep, well-engineered foundations are generally less affected. Lightly loaded structures with shallow foundations, including many homes and budget-constrained public buildings, carry more risk.

How is expansive soil risk actually tested on a specific site?

The consolidation swell test is used for building foundation design, and the California Bearing Ratio swell test is used for road and pavement design. Both require site-specific soil sampling rather than relying on general regional assumptions.

What can be done during site development to manage expansive soil risk?

Grading and drainage design that actively directs water away from foundations, moisture control during and after construction, and foundation systems designed around site-specific swell testing are the primary tools for managing this risk.

Plan Your Site Development Around Actual Soil Conditions

Expansive soil conditions vary across a single site, and grading decisions should be based on what the ground actually does, not a general assumption. Talk with our team about your project, or learn more about our civil construction and excavation and grading services.