New Children’s Hospital puts pilings to the test

3 - sun photo

The new Children’s Hospital of Saskatchewan (CHS) is currently under construction in Saskatoon. When operational in 2019, it will be the first of its kind in the province – a five-floor, 176-bed facility that will offer specialized medical services for children, teenagers, pregnant women, and mothers. It will also include a pediatric and adult emergency department for both the CHS and the existing Royal University Hospital (RUH), which is located adjacent to the CHS.

“Many of the specialized services that are going to be offered by the CHS are currently dispersed throughout the region and at different locations within existing facilities,” explains Craig Ayers, Children’s Hospital of Saskatchewan project director, Saskatoon Health Region. “In some instances, patients currently need to relocate within a department or between facilities. This new facility will allow specialized services to be co-located under one roof. It is a very significant and complex project.”

Site situation
Construction of the new CHS is made all the more complex because it is being built on the site of the existing RUH. As such, there was extensive site preparation work involved. This began in 2011, and included the creation of a new entrance to the RUH, expansion of a portion of the parkade and demolition of an area of the parkade in the area of construction of the new facility.

“This is a complex project in that it is being integrated into an existing, live site,” notes Tom Bain, senior project manager, Graham Construction, the general contractor on the project. “The new hospital is located between the existing Royal University Hospital and the parkade. This means we have both operational restrictions and access restrictions.”

Not only does the “live” site translate into tight building conditions, it also gives rise to other concerns.

“One of the main challenges is logistics,” says Bain. “We have a very limited area – what we call a ‘gap site’ to bring in materials and resources. We’re working in a live hospital environment and have to deal with just-in-time sequencing of materials delivery. We also have to manage the comings and goings of the general public, the physicians and other staff. It’s a tough logistical situation.”

3 - 40Planned piling
The first phase of construction on the CHS involved 240 cast-in-place (CIP) concrete piles. The company charged with the work was Deep Foundations Contractors Inc. They began the job at the end of September 2014, and finished in February 2015.

“We worked through the winter but didn’t miss any time due to bad weather,” says David Bradshaw, regional manager, Western Canada, Deep Foundations Contractors Inc. “It just took a bit longer to warm up the equipment when working in minus 25 or minus 30-degree temperatures.”

Despite the extra time required to ready the equipment, Deep Foundations Contractors finished the first phase of piling work slightly ahead of schedule. That’s not to say it was an easy job.

“It was quite a complex project,” explains Bradshaw. “The ground conditions varied tremendously across the site. We had to constantly adjust the pile depths that were required.”

According to Bradshaw, the geotechnical information provided prior to the start of the project was limited because of the existing RUH parking structure that was located on the same site where the pilings were to be installed. The preliminary test holes were done primarily along the periphery of the site. Additional geotechnical testing was completed once the parking structure was demolished.

“We had anticipated a range of depth of between 15 to 20 metres,” says Bradshaw. “We ended up with a range of between 15 and 33 metres.”

Fortunately, the company had additional capacity on site to deal with the extra depths required.

“We did have to make some modifications to the way we handled the reinforcing cages,” adds Bradshaw. “We constructed a cage handling cradle to deal with the long cages safely. Additional reinforcing was required as well.”

The majority of the piles required a “bell” to be constructed at the base, which typically tripled the diametre of the base, in order to increase the bearing area and therefore, the pile capacity.

The pile design was based on a combination of shaft friction and end bearing to develop pile capacity,” adds Bradshaw. “A greater shaft length was required when we encountered a layer of less-consistent material than assumed in the pile design, which meant piles had to be drilled deeper. It was essentially ‘real-time design.’”

3 - BG28Restricted access
Another significant aspect of the piling work was the limited access that the crew had to the site.

“It was a real challenge,” says Bradshaw. “We were hemmed in on three sides with the access limited to a long, single-lane driveway. Contractual conditions restricted the times of day when construction traffic was allowed to access the site. It took a lot of good site planning to manage this constraint. The adjacent University did not want our supply trucks and equipment traveling through the University grounds during times of peak pedestrian and vehicular traffic as a safety precaution.”

Although the restricted access from the “gap” site had the team of 10 people sometimes working into the evening, it didn’t involve night work. And, it didn’t delay the schedule.

But the more complex scenario is yet to come.

“Phase two will involve about 60 piles,” explains Bradshaw, who adds a new ramp has to be constructed in order to close the existing ramp into the parking structure and maintain continuous access into the parking-structure grounds, as well as allowing for construction of the main hospital building. “Phase two will be very congested. I would estimate that about three quarters of the existing site will be eliminated due to other construction activities. Plus, there will be the added traffic from the trades that will come with the building of the new hospital. It’s going to be very tight – no doubt about it.”

Bradshaw estimates this part of the piling work will begin at the end of February 2016, and run for a couple of months at least.

“It would have been a lot easier for us to do the two phases at the same time,” concludes Bradshaw. “But given the fact that the new hospital is being constructed on the existing site of a hospital that needs to remain operational, it just turned out that we had to do it in two phases. The first phase was tight. But the second will be tighter still.”