Deep Drilled Pier Foundations Near the Foothills
Where the foothills begin west of Fort Collins, the ground stops behaving like the flat plain to the east. Bellvue sits at the mouth of Rist Canyon, and Horsetooth Reservoir fills the southern part of the neighboring Pleasant Valley behind four earthen dams completed in 1949 and seismically retrofitted between 2000 and 2004. Sites in that terrain often have a thin layer of soil over bedrock, or fill that cannot be trusted to carry a building. Drilled piers are what let a structure reach past those layers to material that can.
We build drilled pier foundations for owners whose engineers have concluded that shallow footings will not do. That includes heavy industrial equipment, tall or lightly loaded structures with uplift, buildings on slopes and sites where expansive or compressible soils are found. The work is a collaboration among the geotechnical engineer, the structural engineer and the drilling crew, and we try to make sure each hears from the others before a hole is drilled.
Elevation, Slope and Soil on the Western Edge of the Market
The northern Front Range spans a range of elevations. Fort Collins is at the edge of the plains, and Estes Park sits at 7,743 ft elevation at the eastern entrance to Rocky Mountain National Park. Moving up the Big Thompson, the conditions change: more rock, steeper sites and more demanding access.
In Bellvue and Laporte, along the Cache la Poudre as it leaves the foothills, the ground changes within a short distance, so each site needs its own investigation. A neighbor's boring log is not a substitute. We recommend a geotechnical program sized to the building rather than to the minimum the lender requests.
Drilling, Reinforcing and Placing
The scope we manage covers layout, drilling, temporary casing where required, reinforcing cage fabrication or delivery, concrete placement and pier-top finishing. Cages are inspected before they are set, and concrete is placed by tremie or by pump as site conditions dictate. For each shaft we keep a log showing depth, material encountered, time and concrete volume.
Those logs are more useful than they might sound. They tell the geotechnical engineer whether the soil matched the boring data, and they give the owner documentation if the building is ever modified. We deliver them as part of closeout and tie them to the survey of as-built pier locations, so the structural engineer can confirm each shaft against its design location.
Groundwater, Caving Soils and Access
Three conditions drive the cost and risk of drilled piers. The first is groundwater, which can cause caving and requires casing or slurry methods. The second is obstructions such as cobbles and old foundations, which slow drilling. The third is access: a drill rig is a heavy machine, and a soft or steep approach can stop work.
We address each in the plan. A haul road with a prepared working platform keeps the rig stable, and spoil is moved and stockpiled where it will not block the next shaft. If your project involves a steel frame, our pre-engineered metal buildings experience helps with anchor rod layout, which has to land within tolerance on top of the pier.
Design Criteria and Inspection
Under the Fort Collins code set, the 2024 International Building Code with local amendments applies to permits submitted on or after April 1, 2026, and the city's design criteria include a 30 inch frost depth and Seismic Design Category B. Piers are normally far deeper than frost depth, but the criteria still govern the grade beams and caps that connect them.
Special inspection is typically required for drilled piers. A special inspector observes drilling, measures depth and verifies the reinforcing and concrete placement, and we schedule our work so that they are present for each shaft. The inspection record forms part of the permit closeout and is something the owner will want to keep with the building file.
Where Piers Make Sense
We see piers specified most often for aircraft hangars with large door spans, for industrial buildings with heavy crane or process loads, for buildings on sloped ground, and for structures with significant uplift from wind or snow drift. The aircraft hangar is a good example, where door-opening loads and the need for a stiff floor often drive deeper foundations.
Education and institutional owners sometimes encounter piers on campus sites that carry old fill or utility corridors. If you are planning a building for an education institution on a constrained site, early coordination between the geotechnical engineer and our design and build delivery team can often settle the foundation type before drawings are developed too far.
Sequencing Piers with the Rest of the Job
Piers are normally the first structural element on a site, which gives them an outsized influence on the overall calendar. A drilling program that takes longer than expected pushes grade beams, steel delivery and the building enclosure back with it. We schedule drilling during the stretch of the year when access is most reliable and prepare the working platform before the rig arrives.
Drilling also sets up a run of inspection milestones. Each shaft is observed, the reinforcing cage is approved, concrete is placed and cylinders are broken, and only then can caps and grade beams proceed. We build those milestones into the schedule explicitly, so that the owner can see the dates when the structure becomes ready for the next trade rather than discovering them when a delay occurs.
Working Safely Around Open Shafts and Heavy Rigs
Open shafts are a serious hazard on a site where people and equipment move all day. We cover or barricade every open hole, keep a clear exclusion zone around the rig and control access for other trades. Spoil is removed on a schedule to prevent traffic through slick material, and workers near the rig are trained on its swing radius and the signals used.
Reinforcing cages are heavy and awkward, and setting them requires a crane or the rig's own hoist. We plan every pick, inspect rigging and keep non-essential people out of the pick area. A site that is quiet and organized is generally a safe one, and it is also easier to inspect.
Bring Us the Boring Logs
Send the geotechnical report and the pier schedule. We will tell you what drilling method we expect to use, what the risks are and how we would sequence the shafts.
Questions Owners Ask
How do we know whether we need drilled piers or can use spread footings?
The geotechnical report makes that call. It will report allowable bearing pressure, depth to competent material, groundwater and expansive soil potential. If shallow footings cannot meet the structure's loads or movement limits economically, the engineer will recommend piers or another deep system.
How long does a pier program take to drill?
It depends on diameter, depth, soil and the number of shafts, so we avoid quoting a typical figure. A small building with a few dozen piers may take days; a large industrial structure can take weeks. We give a production estimate after reviewing the boring logs and the pier schedule.
What if we hit groundwater or caving soil mid-drill?
We switch methods, using temporary casing or slurry, and we notify the geotechnical engineer immediately. The contract should state how such conditions are handled, and we recommend agreeing on unit prices for casing or additional depth before work begins.
Can piers be installed in winter?
Drilling can continue in cold weather, but concrete placement requires protection. Frost in the soil at the top of the shaft needs attention, and cold affects equipment. We plan placement for the warmest part of the day and protect the shaft tops afterward.