Soil stabilization lays the groundwork for Colorado’s largest construction project.
By Shawn Fitzhugh, P.E.
A short distance from Denver International Airport, in Aurora, Colo., work is underway on the Gaylord Rockies Resort and Convention Center. Set on 85 acres, with 2 million square feet of conference and hotel space planned, the Gaylord Rockies will be the state’s largest combined hotel and convention center. Even before completion it is breaking construction records as one of the largest projects ever built in Aurora and one of the largest hospitality projects to break ground this year in the United States. To make it all happen, nearly 10,000 construction employees will be needed over the course of the two-year project.
But first, they need to get there.
Initially, CTL|Thompson, a Denver-based geotechnical, structural, environmental, and materials engineering firm, was hired to manage groundwork and foundations for Gaylord’s initial construction phase. CTL’s initial punch sheet involved providing compaction testing and drilled pier observation and inspection. But when heavy trucks carrying concrete for the caisson foundations sank into the ground instead of delivering their payload, general contractor Mortenson Construction had a problem.
Working with WELBRO Building Corp. through a development partnership led by RIDA Development and Ares Management, Mortenson called on CTL’s materials testing and design experience and added “design access road” to CTL’s scope of work.
The CTL team knew that delivery and construction delays could demolish the overall timeline for a resort expected to generate more than $7 billion in economic activity and 1,500 permanent jobs. When the heavy concrete delivery trucks sank deep into the soft ground, they didn’t just halt the caisson drilling. The immobile trucks blocked all other traffic from accessing the site. It was highly probable that other heavy equipment, such as a flatbed truck with reinforcing steel, would have similar problems.
The existing temporary access road and parking area were constructed of asphalt on compacted onsite clay — a typical design for the region. In its review, CTL recognized that the combination of the area’s extreme weather conditions, the makeup of the soil, the sheer size of the equipment, and the traffic created by the 10,000 employees required for the job was just too much for the road to withstand.
To shore up the ground below the temporary pavement, the CTL team recommended a feasible solution that has proven reliable for soils found below permanent roads — chemical stabilization. The technique mixes lime and cement with onsite soils to create a firm, stable base for asphalt.
Chemical stabilization helps to compact soil, alter the behavior of clay soils, aid in water drainage, and keep dust down, all crucial factors to consider as work carries on through distinct Colorado seasons. The technique has a long life span — critical for a project of this size and scope — and requires little maintenance while construction is ongoing. In some cases, chemical stabilization can be more expensive than other stabilization techniques, but on this job, CTL projected that the solution would cost less than other options, in addition to being much more effective than the original design of asphalt over compacted onsite soils.
The benefits were clear, and the ground is now being chemically stabilized in phases. Temporary roads are being placed first, and permanent roads will follow. The entrance access road is finished, with no significant issues encountered thus far. Trucks and personnel now can do their jobs without unexpected logistical challenges, at least where the road is concerned.
In a project of this size and complexity, the seemingly inconsequential access road became a major player in completing construction on time and under budget. In addition to assisting the monumental Gaylord project, the soil-compaction solution will inform continuing construction in the Denver region as more projects are planned for open, undeveloped areas like the area where the Gaylord is in progress.
The solution is surely informing CTL’s ongoing work. Whether a development is large or small, commercial or residential, access roads are the first step in project planning. Thanks in part to the insights gained from this project, access conditions are among the first questions CTL asks its clients when determining scope. The groundwork for a successful project starts here, with forethought providing a team with its best advantage.
Shawn Fitzhugh, P.E., is field services manager for CTL|Thompson (www.ctlthompson.com), a full-service geotechnical, structural, environmental, and materials engineering firm based in Denver.