Taylors Contracting was involved in the Tekapo Canal Remediation project. Repairing the canal, built in the early 1970s, was time critical. Every time the canal was dry the owner, hydro generator Genesis Energy, was losing big money. BY ALAN TITCHALL.
TIME WAS OF THE ESSENCE in this project as the canal shutdown windows were very limited, so forward planning for the project was very important, says Taylors Contracting managing director, Charlie Taylor.
“The entire project was wrapped in extremely tight time frames with no extensions as the operational costs to Genesis were significant.
“There was a huge amount of pre-planning, with everything planned to the half day. We did trial work to test our systems prior to the canal shutdown so we knew how things were going to pan out, including the processes of how we were going to put the liner on.”
Although an engineering feat back in 1977, the 26.5-kilometre Tekapo Canal leaked from day one due to the engineering techniques employed back then. The earth lining was a clay-bound glacial till on top of gravel. Once the clay was breached, the water poured through the gravel like a drain.
After three decades the canal liner had deteriorated to the extent that the water loss was estimated to be substantial. The canal also needed to meet current building standards and earthquake risk.
The current canal owner, Genesis Energy, searched worldwide for a solution and eventually chose a liner imported from Europe. Carpi Tech, canal remediation experts based in Switzerland, were contracted to manage the liner installation.
During the first half of 2012, Taylors Contracting joined a team of contractors and engineers, including Fulton Hogan, Carpi Tech, and URS to develop a construction design with Genesis Energy.
Preparations started in September 2012 for the first season shutdown in January 2013 – a 14-week period to complete the first five kilometres of relining.
“This project was different in that the contractors were selected before the design and price were negotiated,” says Charlie.
Taylors Contracting’s scope of works included site establishment and disestablishment, construction and deconstruction of coffer dams, canal reconstruction, canal subgrade treatment, quarrying, canal embankment works, and reinstatement works.
“The success of the project involved a huge amount of planning. Before work started we were involved in full scale construction trials, including building a replica section of canal to the same depth and grade.”
Charlie says this planning phase also clarified to all parties the imperatives of quality and time, particularly around the outage schedule, which called for multiple contingencies.
“The allocation by Genesis of a substantial period for this project planning was critical to the success of the project.”
While each contractor had a specialist role, collectively they had to come up with a “balanced solution” so that all work streams advanced in parallel. Suffice to add, the project demanded a close working relationship and bond between the management and staff of the principals – Genesis Energy, Fulton Hogan, and Carpi as well as the engineers URS.
“We were all proactive in coming up with solutions using innovative ideas and having good communication lines.”
Methodology – first catch your fish
Construction followed over two seasons in the summers of 2012-2013 and 2013-2014.
Coffer dams were built to close off the section of canal being relined and water was then pumped down to a low level to rescue salmon, trout and other fish that were relocated to another part of the canal.
“A lot of fish,” Charlie adds, as there is a salmon farm downstream from the project works.
“Around 800 salmon and trout, plus thousands of native ‘bullies’ were removed from the canal as part of the preparation.”
The environmental value of the project was imbedded in the tender process.
“Measures were encapsulated in various conditions of the 41 consents issued by the Canterbury Regional and Mackenzie District Councils,” says Charlie.
These consents required the preparation of a detailed Environmental Management Plan for works, supported by another 11 supplementary environmental management plans addressing specific risk areas including storm water control, sediment and erosion control, dust control, and noise management.
The project was located about 15 kilometres south west of the Lake Tekapo township, which is a popular tourist region and well-used by recreational fishermen. The road along the edge of the canal was closed during the construction works.
The installation and construction of the coffer dams was also a major potential issue and extreme care had to be taken to ensure that a safe working environment was available to all staff working downstream. Once in place, the water was over pumped to the downstream coffer dam so there was a dry surface for the construction works to take place.
First outage and construction January to April 2013
With the section of the canal emptied, Taylors Contracting was charged with ‘mucking out’ the canal floor; removing the original frost protection; completing the subgrade treatment and excavation and backfill for the replacement of under-canal culverts; embankment repairs; and trimming and rolling batter slopes in preparation for the liner installation.
“Once the surface was approved we put a 50mm layer of sand on the canal surface and then the liner was laid on top and its sections welded. We put another 50mm of sand on top of the liner and Fulton Hogan placed ballast on the bottom to hold it down.”
Reinforced aggregate ballast was constructed on each canal crest, and then the coffer dams removed and the canal refilled.
“Removing the silt laden material and old frost protection layer from the canal floor was a potential issue,” says Charlie.
“Dump trucks could not travel on the canal floor so a methodology was devised to construct a haul road down the batter slope of the canal by cutting into the embankment, so the trucks could remove material from the floor to the dump site.
The batters were then prepared for the lining contractors following their progress.
“When the batters had been trimmed off, they still needed to be compacted to allow for a steady platform for the liner to be installed.
“It was decided to set up winches on the rear of John Deere JD700 dozers. Fitted to these winches were two, four-tonne drum rollers that were lowered down the batter slopes to the base of the canal and then winched back up. This was done progressively and methodically throughout the project.”
This innovation was among many developed by Taylors Contracting.
On top of the liner, there was a layer of sand, a layer of geo-grid, with a final layer of frost protection placed for the canal invert.
The thickness and placement of the sand-blinding layer through the remediation areas was critical, Charlie adds.
“Dump trucks imported the material to the work area where it was placed with an excavator equipped with a long-reach boom and levelled using Trimble’s Machine Control.
“The geo-grid was rolled perpendicular to the canal flow and a final layer of frost protection placed on top, again using the Trimble Machine Control.”
The liner system integrity objective was to minimise defects with an expected achievement of less than one unacceptable defect per 4000 square metres – an unacceptable defect being a puncture of one square centimetre or more.
“Due to these tight directives, it was essential that the liner base was smooth and free of imperfections and sharp edges,” says Charlie.
Throughout the project there were up to eight machines with guided GPS on the site.
“We also use Trimble Business Centre survey software for calculations, design and setout applications.
“This technology allows extra room for the operators so they don’t have to work around setout pegs and is therefore a saving on costs due to not having to constantly be setting out pegs by a surveyor for line and level.”
Stage one of the project, a five kilometre stretch of the canal linking the Tekapo A and B power houses, was completed in April 2013.
Stage two, during January to March 2014, involved a two kilometre stretch on the ‘Maryburn Fill’, which was completed in March 2014, more than a month ahead of schedule.
“At the completion of the first construction period, a full debrief was held over lessons learned, which could then be put in place for the next season, and a second wave of project planning with improvements developed which were implemented in the second stage,” says Charlie.
Graphs were completed on a daily basis and displayed on notice boards in the morning tea room so that all workers on site could see how progress was being made against the programme for all streams on a daily basis.
Due to the nature of the project works, and the other civil contractors working on-site, communication was key to a successful injury or incident free worksite.
Daily catch-ups were held between contractors to discuss where each contractor was heading – to arrange access through the site and general site issues.
The health and safety plan was developed by the whole project management team.
“All stakeholders decided to work under Fulton Hogan’s Golden Rules and all staff were encouraged to actively bring up any issues or potential issues that they may have encountered during the day, so control can be put in place before any major issues arose,” says Charlie.
“A site-wide health and safety manager was put in place for all parties on site and the different parties involved in the project were all located within one communal work area to allow for easy communication during the project.”
Taylors Contracting recorded no serious harm, minor or major incidents, or lost time injuries, he adds.
It was bloody cold up there
The overall project timetable, from initiation in June 2011, to completion in March 2014, was in itself a remarkable feat for a project of this complexity and scale.
“We were working on a high level in a remote alpine area, with tight deadlines, and difficult technical conditions.
“The operations and teamwork between the different organisations worked together as one functioning unit including workers from different cultures including Hungary, Germany, and Italy.”
Any surprises during the project?
“Sure – we thought we could keep well in front of the liner guys, but they were right on our tail the whole time.
“And we found some old firearms and swords someone had thrown into the canal. They were quite rusted, but the Police picked them up. We also underestimated the effect of the wind and on one day we had winds gusting up around 130 kilometres per hour.
“During our preplanning the wind records told us that the wind was averaging 110 kilometres per hour and we thought that must have been rogue data – but no it wasn’t.
“Man! It can blow up there.
“It gave us a lot of respect for the guys that built that canal in the first place.”