Drive east along Platte Avenue from the historic downtown core toward the Powers corridor, and you will cross a geological boundary that changes everything about how a hole in the ground behaves. On the west side, near the foothills, you are digging into weathered Pikes Peak granite—competent material that stands up well on its own. Push a couple of miles east, though, and the profile shifts to interbedded sands and silty clays over the Dawson Formation, where groundwater starts appearing at 15 to 25 feet. That transition, subtle from the surface, dictates whether a 30-foot excavation for a parking garage needs tieback anchors drilled into rock or a more flexible soldier pile and lagging system braced with internal struts. Before committing to a shoring layout, we routinely pair the excavation analysis with CPT testing to map the vertical variability across the site, because the stratigraphy here refuses to follow a neat textbook column.
Around Colorado Springs, the Dawson Formation controls excavation behavior: it holds a face until it gets wet, then it slakes, and that changes your bracing loads overnight.
Technical details of the service in Colorado Springs
Risks and considerations in Colorado Springs
Colorado Springs grew in bursts: the Cripple Creek gold rush, the postwar military expansion, and the recent tech influx. Each wave left behind a patchwork of fill, old basements, and undocumented utilities that make urban excavation a forensic exercise. The biggest risk is not the soil itself but what previous generations buried in it. A 1920s-era brick-lined cistern, backfilled with loose ash and cinders, can collapse into the excavation face with no warning. We have pulled old streetcar rail segments and timber cribbing out of supposedly “undisturbed” cuts near the old street grid. Our design process includes a desktop review of Sanborn fire insurance maps and historic aerial photos—low-tech tools that often reveal more than a dozen borings. If the historic record is thin, we tighten the horizontal spacing of soldier piles and add a sacrificial facing layer that can tolerate localized overbreak without compromising the global stability.
Our services
We take the excavation design through three linked stages: site characterization, shoring analysis, and construction-phase monitoring. Each stage feeds into the next, so the modeling never drifts far from the ground truth.
Shoring System Design
Full structural design of soldier pile and lagging, secant pile, or soil nail walls. We develop apparent earth pressure envelopes from site-specific soil parameters, size the steel sections per AISC, and detail the connection between the walers, tiebacks, and pile embedment.
Dewatering and Groundwater Control Plans
For excavations that penetrate the Dawson Aquifer, we design deep well and wellpoint systems to lower the phreatic surface below subgrade. The analysis couples MODFLOW groundwater modeling with slope stability checks to prevent base heave and piping.
Construction-Phase Instrumentation and Monitoring
Installation of inclinometers, optical survey targets, and load cells on tieback anchors. We set threshold deformation values tied to the adjacent structure’s tolerable movement, and provide weekly reports that compare measured behavior to the design predictions.
Frequently asked questions
How much does a deep excavation design cost for a typical Colorado Springs project?
What triggers a dewatering requirement in this region?
If the planned subgrade elevation intercepts the Dawson Aquifer—typically encountered between 15 and 25 feet below grade east of I-25—you will need active dewatering. We use pumping tests and MODFLOW modeling to estimate the inflow rate and design a wellpoint or deep well system that keeps the formation hydrostatic pressure low enough to prevent base instability.
How do you account for the expansive clay seams in the Dawson Formation during wall design?
We take undisturbed Shelby tube samples from the claystone layers and run swell-consolidation tests to quantify the swelling pressure. That pressure is then applied as a surcharge load on the wall face in the structural model. Where the predicted swell exceeds 2 ksf, we include a compressible void form behind the lagging to absorb the volume change without overstressing the soldier piles.