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Heartland Substation I and II

Heartland Substation I and II
Date: 2013

The $596-million Heartland Transmission Line Project, a 66 kilometre line connecting Ellerslie Substation to the Heartland Substation northeast of Edmonton, provides a substantial upgrade to the transmission infrastructure in Alberta. The two key components include a new 500 kV/ 240 kV substation, Heartland 12S, as well as a telecommunications tower within the substation site. General contractor PCL awarded the foundation work for both structures to AGRA Foundations Limited. Heterogenous conditions consisting of silty and sandy clay layers overlaying highly plastic bedrock material presented ideal conditions for cast-in-place bored piles.

Solution:

The AGRA team used two Soilmec drill rigs supported by a Linkbelt 110 tonne crane and APE 200 and 300 vibratory hammers to install a total of 600 cast-in-place piles to 16 m depth. The pile diameters ranged from 610 mm for standard loads to as large as 3048 mm to support the massive transmission towers. The crane and vibratory hammers enabled the crew to install long casings to drill the piles through pockets of sand and water. The crane was also used to hoist and install the immense cages. Close coordination between the general contractor and other subcontractors on site was important as the pile construction coincided with the setting of anchor bolts, pouring of pile caps, heating and hoarding piles.