Ledcor Group of Companies is involved in several different facets of the North American construction industry. Two recent projects, in particular, have brought to the fore the company’s long and distinguished history in the pilings sector. The first is the ongoing work being done at a major oil sands mining operation north of Fort McMurray, and the second is the work being done on ATCO Electric’s Eastern Alberta Transmission Line (EATL) project. These two projects showcase the piling expertise that Ledcor brings to the table.
In the oil sands
Ledcor has been installing foundations for the oil sands mining sites since 2006.
“In 2011, we installed 150 cast-in-place concrete piles and close to 200 guide piles for a mine expansion,” says John Hopkins, project manager, Ledcor. “In February of 2012, we were also involved in a debottlenecking project that required foundation work being installed for the plant expansion, booster pump house, and electrical buildings.”
The foundation work for the booster pump house required the use of tie-down piles with a corrugated steel culvert in the centre.
“The piles were 22 metres long with a steel tension bar in the middle,” explains Hopkins. “The torsion force was going to be so strong that we required two compression piles on the one side and two tension piles on the other side. That way, we could balance the tension force.”
In this case, the tension piles were 22 metres deep and 750 millimetres in diametre. The compression piles measured 17 metres deep and were 1.2 metres in diametre.
The project involved a crew of about a dozen people.
More recently, Ledcor was called into action for further piling work.
“In March 2014, we got involved in a series of smaller projects that involved some cast-in-place piling work, some sheet piling work and some guide piling work for pipelines,” states Hopkins. “The work was mainly in response to some debottlenecking at the plant site and foundation work for an emergency dump pond.”
The piles used in this project were 600 millimetres in diametre and nine metres deep, while the guide piles measured between six and seven metres in length.
“We also installed some large piles for another debottlenecking project,” continues Hopkins, who adds the project required four large piles for the tower crane base, each of which measured 1.2 metres in diametre and was 40 metres deep. “We had to drill using a polymer slurry to suppress the potential gas emissions from the oil sands.”
There were approximately 60 crew on-site who were involved in the piling and concrete work.
Eastern Alberta Transmission Line Project
ATCO Electric’s Eastern Alberta Transmission Line project is comprised of 485 kilometres of 500 kilovolt (kV) direct current (DC) line between Brooks in southern Alberta and the Gibbons-Redwater area northeast of Edmonton. Construction on the $1.8 billion project began in December 2012.
Ledcor was involved in the construction of the EATL AC/DC connections consisting of 25 steel lattice towers split between two locations on the north and south end of the project. This includes 92 large, cast-in-place piles with diametres ranging from 1.52 to 3.05 metres and depths of up to 18 metres. Each tower along the line required a foundation to support four tower legs. The work also included the installation of 64-driven H-pile foundations, of which eight were battered pile, with a steel pile cap welded to the top of each pile.
The towers requiring a cast-in-place foundation also included an anchor bolt setting at the top of the pile used to anchor the tower to the foundation. The assembled anchor bolts consisted of four to 12 anchor bolts, each 55 millimetres in diametre, with lengths ranging from 3.5 to 4.5 millimetres.
Ledcor created custom anchor bolt frames and templates that were used to set the anchor bolts in place during a continuous pour. This effective pre-planning facilitated a seamless setting of the anchor bolts to a tolerance of six millimetres, without creating a cold joint in the pile.
“Our scope of work on the project included two of the smaller lines that connect to the converter stations,” explains Jerrod Dersch, operations manager, Ledcor. “The first line to the Heathfield converter station near Gibbons involved permanent casing up to 18 metre depths with diametres ranging between 2.44 metres and 3.05 metres. The Newell converter station near Brooks required 68 cast-in-place piles for 17 towers in some stiff drilling conditions.”
“The project was unusual in terms of the sheer size of the piles, which were 3.05 metres in diametre and about 18 metres long,” adds Dersch, who says the company had three crews of seven working on the project. “The work also took place in environmentally sensitive areas so we had to conduct the work on access mats in order to minimize impacts to ground cover.”
The environmentally sensitive nature of the project also called for Ledcor to establish stringent reporting processes and comply with ATCO Electric’s rigorous equipment cleaning practices on the job site to avoid the spread of soil borne disease and noxious weeds when equipment was moved from site to site.
The intensive pilings installations completed by Ledcor for ATCO Electric’s EATL project, coupled with the ongoing oil sands mining projects, has demonstrated the breadth and expertise of the Ledcor team in dealing with pilings work of all types and sizes. Both projects highlight the ability of the company to go above and beyond to attain successful completion of what can prove to be a challenging and complex installation. And both projects also showcase the increasingly important role that pilings play in today’s ever-evolving construction industry.