SaskPower 110kV Double-Circuit Transmission Line Critical Tower Repairs

Creighton, Saskatchewan

3 Year Winter Project (2017, 2018, 2019)

• 57 miles of Right of Way (RoW)

• 40+ miles of Ice Road Constructed (Each Year)

• 40+ Miles of RoW trails constructed (Each Year)

• 51 Lattice Towers Rescued and Repaired

• 35 Towers with by-pass Grouted Helical Pile Foundations Installed

• 13 Towers Levelled

• 172 Tower Body Panels Upgraded

• 5 Unique Lattice Tower Types 

The I1F/I2F line runs from Island Falls, Saskatchewan to Flin Flon, Manitoba and was energized in 1930. The line consists of 355 galvanized lattice structures for the span of 57 Miles. The line travels through the Canadian Shield and the Mari Lake Representative Area Network, an environmentally significant and sensitive area, rich in unique vegetation, habitat to the grey wolf, caribou herds and the traditional subsistence grounds of the local First Nation population. The line had undergone a number of maintenance and repair works over the past 35 years. Despite those repair projects there was significant foundation failure occurring. Previous engineering studies indicated probable causes of foundation failures were saturated soils resulting in foundation failure in uplift, frost-heaving and severe corrosion. 

An inspection was completed in 2014 which resulted in the identification of 35 lattice towers in critical condition, and additional deficiencies. The project duration would see construction activities at 15 towers in Y1, an additional 22 towers in Y2 and 14 in Y3 for a total of 51 structures rescued and repaired.

To address and repair the foundation failures, Ampjack utilized a Grouted Helical Pile Foundation option to by-pass the existing foundations, with AMPJACK®’s patented Tower Levelling system. This method would result in minimal environmental impact during installation, requiring no excavation, no dewatering activities, minimal footprint, and minimal disturbance to this environmentally sensitive area.

The primary challenge to completion of the necessary repairs was access.  Due to the remote location, rugged and wet terrain, ground access with the required equipment could only be achieved during frozen conditions.  The line had originally been constructed using Freighting Routes which crossed many lakes and portages along the RoW. It was these historical routes that were accessed for completion of the critical repairs.

Over 40 miles of ice road had to be created during each of the 3 construction years. Establishment of these roads in the short construction window required strategic partners. Big Ice Services was contacted to provide ice road construction services for the project. Utilizing their patented flood pumps and high pressure spray rigs they constructed the ice roads to access the line, in some cases building ice to over 4’ thick.

Once access was achieved the next big hurtle was the installation of the grouted helical pile foundation. No detailed geotechnical information for the work locations was available, so AMPJACK® developed adaptable foundation designs to allow installation of pile groups for varied sub-surface conditions. For this project the solution was the American Piling Equipment (APE) HD-70 drill head. The HD-70 is an excavator mounted drive head, which through the use of various drilling attachments allows for the installation of pressure grouted helical piles, into soil, gravel, sand or rock socket without the need for additional equipment.  This installation method ensures a solid bond between the pile and the subsurface material. Over 90% of the pile installations were into bedrock at depths between 10’ and 40’ below grade.

The transmission line is a radial feed which supplies power to a number of isolated communities and is also part of an interprovincial link. Due to those factors acquiring an outage to both circuits is virtually impossible. These conditions along with the difficult access, challenged Ampjack to develop an outside-the box method for the levelling of the leaning towers that did not require an outage, crane or other heavy construction equipment.

Our engineering team displayed their capabilities yet again by utilizing technology from our AMPJACK© Tower Raising System and incorporating it with the foundation upgrade design to provide a solution that allowed for repositioning of the tower while under live line and live load conditions.

In conjunction with the foundation repairs there were significant lower body panel upgrades required to correct some of the tower body modifications completed in previous years and provide the necessary structural support for continued service in the years to come.  Over the years, Ampjack has developed extensive experience developing tools and procedures to repair many different tower types under many differing load case scenarios. We utilized our panel replacement tools and procedures to complete this work while under live line and live load conditions.

This multi-year project was a challenging one and could have only been completed through the hard work, focused efforts and commitment of our dedicated team and partners. Each year’s scope was completed on time and on budget with no lost time injuries, no environmental incidents and no stop work orders. We used this project as an opportunity to demonstrate our commitment to safety and complete our external COR Safety Management audit during the project.