From canceled flights and dangerous commutes to schools and activities being canceled, most of us have felt the effects of inclement weather.
Record-breaking low temperatures, considerable snowfall, and high winds can pose extreme challenges on a construction site. To combat winter conditions and avoid delays, PCL Construction provides innovative solutions, extensive planning, and close collaboration.
Construction on the Altru Hospital Replacement project has posed several challenges due to its location in the coldest city in the continental U.S., Grand Forks, North Dakota. The project has spanned three winters and includes a 550,000-square-foot, 212-bed hospital with seven stories above grade and one below.
Cold weather has required the use of temporary heat to complete temperature-sensitive scopes and to keep tradespeople warm. The project team opted to utilize open-flame natural gas heaters which require a fire and smoke monitoring plan. With up to 25 open-flame heaters operating on the project at one time, periodic site checks did not seem sufficient. The team implemented a do-it-yourself 24/7 monitoring system that could detect and respond to an issue immediately.
The Altru project has also been affected by high winds, which intensify the cold and make hoisting and installing materials difficult. Reinforced polyethylene plastic sheeting is commonly used to provide temporary protection from wind and precipitation until permanent walls can be installed. The team knew from past experience that this material tears easily and began investigating other options. They decided to use a shrink-wrap system created by Global Wrap, which initially designed the system for boats. The temporary shrink-wrap system is made of 12-mil, fire-retardant shrink-wrap film, aircraft cabling and adhesives, and is fastened to the building using wood blocking. According to project superintendent Jon Stoeckman, the product, “hasn’t failed once and has allowed the project to remain on schedule.”
The team’s upfront planning and solution provider mentality has enabled PCL to overcome the cold temperatures and strong wind. The Altru Hospital project is on track to meet its substantial completion date.
While solar energy is abundant in warm, sunny southern environments, it is increasingly utilized in colder, snowy northern climates. Approximately two-thirds of solar projects completed by PCL have been constructed in areas susceptible to frost heaving. This geotechnical phenomenon occurs when frozen ground or frost stops forming from the ground surface downwards and water from the unfrozen soil below is drawn upwards into the freezing zone. The collecting water forms growing ice lenses that push upwards and cause the surface to heave up to four inches in a single day. Frost heaving typically occurs in early spring when temperatures begin to rise. It is most common in colder, northern climates with fine-grained soil such as clay that does not drain well.
Frost heaving puts stress on foundations, racking systems, and electrical infrastructure. Deflections, cracked modules, and damaged wiring can lead to costly repairs. It can also decrease energy outputs and the project’s lifespan.
PCL’s Solar group has a design and analytics team that provides solar design and performance modeling and testing in-house. The team optimizes design and mitigates construction risks including those related to frost heaving. One method they utilize to prevent damage caused by frost heaving is using helical piles in lieu of driven H piles, which are commonly used in frost-free southern areas. Helical piles are an economical and effective alternative. Each pile has one to three round steel plates that are arranged in a helical pattern around a central shaft and are embedded below the frost line by twisting the entire pile in like a giant screw. Unlike most driven piles, helical piles withstand the potential uplift forces due to frost because the plates keep them fixed firmly in place.
Cold weather conditions pose additional challenges to solar projects beyond design. With sites ranging from 1,000 to 3,000 acres, traditional methods of ground thawing are not feasible. In order to maintain a project’s schedule, Brad Hise, operations manager for PCL’s U.S. Solar group emphasizes the importance of “strategizing with the owner early on to get the work activities completed and have a strong upfront plan.” Grading, cable trenching and backfill, roads and piles, and other underground activities should be completed prior to winter. Above-ground work such as racking assembly, PV module and above-ground electrical cable installation, and electrical terminations can be completed during the colder months.
Another method PCL has found to be successful is changing DC cabling from underground installation to above-ground cable management systems. This allows for the work to be installed during winter months and also reduces cabling size due to the natural cooling factor of being above ground.
With more than 60 solar projects built to date, PCL’s design and construction methods have proven successful. Despite the many challenges winter weather poses, PCL has hit contractual milestones on more than 95% of its solar projects to date.
Innovative solutions have helped combat winter-weather-related challenges on the Tree Top Trail project at the Minnesota Zoo in Apple Valley, Minnesota. The 1.25-mile-long trail is set to be the longest elevated pedestrian loop in the world and has a peak height of 32 feet. The trail is being constructed on a decommissioned monorail track. Challenges related to near-record snowfall have been compounded by the construction process occurring exclusively from the elevated trail.
The team needed to find a way to warm tradespeople without them getting down off the trail. After deliberating several ideas, they opted to use ice fishing houses. The houses are placed on sections where the trail width expands from eight to 12 feet and can accommodate up to four people.
Snow removal from the trail has also required creativity and collaboration. The team needed to find a more efficient solution than shoveling by hand. They decided to attach a 16-inch ATV snowplow to the front of a trolley. The client has also valued PCL’s partnership with testing different snow removal methods to be used once the trail opens, which is on track to occur ahead of schedule.
The unpredictable nature of winter weather requires proper early planning, collaboration, and a bit of creativity. With a long history of successful, on-time project completions in even the most frigid climates, PCL continues to find innovative solutions to winter-weather challenges on projects across North America.