CREJ - Building Dialogue - March 2017
When looking back at Denver’s real estate history, we often talk about “land,” especially “developable land.” Developers, contractors and the media use the term broadly, but geotechnical engineers see beyond just a parcel of land to the soil, rock and other unique geological conditions that, in Colorado, can make developing a parcel challenging. Most land in metro Denver is made up of expansive soils, which, true to the name, expand when water is added, resulting in building and infrastructure movement. The Front Range’s coal mining history adds further potential instability, as former underground activity may result in subsidence that impacts construction. And at the deepest levels, expansive bedrock is tipped due to the uplift of the Front Range, resulting in unusual heave in some areas and the potential for significant movement that could damage roads and building foundations if not properly mitigated. During Denver’s initial building boom of the late 1970s and 1980s, these geologic conditions wreaked havoc on developments in the form of subsidence, expansion and heave, landslides and structural damage legislation. Yet Denver’s unique geologic landscape also attracted some of the best minds for solving these problems – geotechnical engineers who have devoted their lives to mitigating geotechnical risks. These experts have opened development on previously undevelopable land and ultimately built foundations for where we live, work and play. The techniques that made today’s growth possible started in the residential sector. My mentor, and CTL|Thompson’s founder, Bob Thompson identified new testing and mitigation techniques while conducting geologic and geotechnical investigations, earthwork observation and concrete testing for housing developments that were popping up in Golden, Applewood and Littleton. Initially, Thompson developed advanced soil testing that included drilling more borings per acre and to a greater depth than previous industry standards dictated. The new tests delivered knowledge that informed innovative building methods such as deep-drilled pier foundations and structural floor systems. As a result of this information, developers could build homes in formerly high-risk areas near hogbacks and one-time coal mines. Shoring up exterior flatwork and garage slabs followed. In the 1990s, after tireless laboratory and field effort, our team began to excavate expansive soils and replace them with moistened fill, reducing expansion potential and improving the performance and safety of slab-on-grade foundations, basement slabs and garages. The advancements used in residential building ultimately opened a path for commercial development growth. Extensive soil testing provided a better understanding of soil heave conditions that can affect low- to medium-rise commercial office, warehouse, industrial and retail buildings. At the same time, a better understanding of the support characteristics of the bedrock underlying central Denver has also allowed for economically practical solutions that support buildings with heavy loads, such as office, and paved the way for many of the high-rises currently under construction in all sectors – office, residential, hotel and retail. Geotechnical engineering solutions have “paved the way” for new building and actually have paved the road to make construction possible in new developments. Most recently, our geotechnical team, supported by our materials testing division, designed an access road for construction on the Gaylord Rockies Resort and Convention Center, one of the area’s largest hospitality projects under construction. When Gaylord work began, insufficient construction roads could not support heavy concrete trucks, which sank into the ground, causing major delays. Together with Mortenson Construction, we chemically stabilized the soil under the access roads, repaved them with asphalt and created a thoroughfare to allow construction to continue with minimal delay to complete the hotel, proposed to generate more than $7 million in economic activity annually once open. Sites like the Gaylord Resort’s 85 undeveloped acres are uncommon, however. Luckily, as the metro area expands, so do engineering methods that can create developable land from brownfield and infill sites, creating economic opportunity on land that was formerly barren and untouchable. For example, through sound testing and creative engineering, Metropolitan University completed its Regency Athletic Complex on a former chemical facility, and the Community College of Denver constructed its Student Learning and Engagement Center on a site that once housed a gas station, a streetcar substation and a biscuit factory. Le Meridien Denver Downtown could quickly work around an unexpected dormant foundation thanks to an environmental assessment, and Taxi is now the workplace of dynamic new energy companies thanks to remediation of the old Yellow Cab facility and solid waste landfill formerly on the site. In 2016, the Metro Denver Economic Development Council reported that more than 7.4 million square feet of commercial real estate space was completed, a whopping 45.4 percent increase over 2015. Jobs continue to be added to the economy at a pace that is keeping up with the net increase in migration. Given these stats, developable land – and the soils and rocks that comprise it – will stay in great demand. Developers and builders can count on the engineering community, which is geared up with tools and techniques to ready raw land for construction and make old land new again. PHOTOS: CTL|Thompson OPENING ART: CTL|Thompson turned a brownfield site littered with environmental hazards and detritus into developable land that now holds Metro State College of Denver’s Student Success Building. ABOVE TOP: CTL was hired to manage much of the ground work for Gaylord’s initial construction phase, but after concrete trucks sunk, the team shored up the ground with chemical stabilization, a solution usually used on permanent roads. ABOVE BOTTOM: On 16M, CTL’s concrete experts found a solution for concrete that wasn’t meeting compressive strength, shoring up the 340,000-square-foot building. RIGHT: During work on the 31-story One Lincoln Park.... condominium tower at 20th and Lincoln streets, fuel tanks were found buried on the site. CTL recommended abatement strategies and now the iconic tower houses some of the hottest condos on the market.