Two of Ireland’s largest windfarm projects have been constructed on behalf Bord na Mona, Ireland’s leading producer of peat based products and now renewable energy and recycling, at its Bruckana peat bog site in Tipperary and Mount Lucas site in County Offaly.
The new windfarms will be capable of supplying electricity to 45,000 homes once fully commissioned. The Bruckana windfarm includes, 14no. 3MW turbines plus a new 38kV electricity substation. The Mount Lucas 84MW windfarm will have 28 wind turbines, plus an 110kV electricity substation. Work on both sites also includes, 31km of new access roadway, as well as crane hard standings and underground cables. Groundforce was subcontracted to two main contractors working on the projects both directly and via subcontractors.
Being able to supply such a wide range of specialist equipment from the six Groundforce divisions, Shoring, Piling, Pipe Stoppers, Shorflo Pumps, U Mole and Temporary Bridges, from any one of the company’s depots in Ireland is a unique boast of Groundforce Ireland, and enables the company to provide a total solution for civil engineering schemes across all of Ireland.
Bruckana Wind Farm
Challenges & Solutions
At the Bruckana site there were three main challenges - poor ground conditions, the large size of the foundations and a tight construction programme.
Because the site is a peat bog, the ground conditions were very poor when it comes to load bearing for structures. The ground was so soft that three of the 10 pylons carrying the 110kV power lines required larger than standard, specially designed foundations. In normal ground conditions, pylon foundations for 110kV lines have four separate bases, each 4m x 4m square and 3m deep but due to the poor bearing capacity of the peat and underlying soil strata, 12.2m x 12.2m x 6m deep foundations were required to ensure stability for a number of the pylons.
Main contractor Gaeltec sub-contracted the foundation works to ESK Plant Hire, Groundforce assisted ESK by providing a turnkey solution with specialist piling, shoring, de-watering and trenchless technology equipment, all supplied from their Portlaoise depot. Groundforce supplied KD6 and interlocking GFI trench sheets, an MS4 excavator mounted piling hammer, Mega Brace hydraulic shoring frames and HSK150 hydraulic struts to support the 12.2m x 12.2m x 6.0m deep excavations.
The company also provided design services to ensure optimum structural support. Each excavation had three levels of bracing. The lower two bracing frames were fitted with knee braces in the corners to withstand the high lateral loads of up to 112.5kN/m.
The sodden peat soil posed an additional problem, with high water ingress into the excavations. This was tackled with a number of fuel efficient 6”100mm super-silent diesel pumps, which were on hire for the duration of the contract.
Another potential problem arose when cable ducting had to be brought underneath a light rail track, used by the client for transporting peat from the site. Rather than dig up the track, ESK chose to use a 130mm hammerhead rammer and locking collets to ram a 150mm steel tube underneath the track. The ducting was then threaded through the steel tube without any disturbance to the track.
ESK and Groundforce worked in extreme weather and ground conditions to construct bases for the specially designed pylons.
Groundforce’s experience and technical backup combined with ESK’s civil engineering skills, ensured the project was completed in a safe and timely manner and we look forward to working with Groundforce again in the future.
Tom Holland, Commercial Manager - ESK Plant Hire
Mount Lucas Wind Farm
At the Mount Lucas windfarm development, Groundforce were working directly for main contractor PJ Carey on the drainage works element of the programme. Over a 12-month period Groundforce supplied a total of 14 of its super silent pumps. These included both its 4” and 6” high performance silent pumps, which are capable of handling clean or dirty water and sewage.
Located on a former milled peat production site there was a lot of ground water to be controlled. The Groundforce pumps were used to remove the excess water on the areas surrounding the turbine bases as these needed to be kept dry to allow the steel reinforcement to be installed along with the erection of formwork for the pouring of the concrete bases.
It was important for PJ Careys to have in place a system that was both reliable and cost effective as the pumps were required to work seven days a weeks to keep the working areas dewatered.
Using Groundforce pumps resulted in significant cost savings on fuel. The pumps also eliminated the need for refuelling over the weekends, and as the equipment is all new, there were fewer breakdowns which also saved on downtime.
The 4” pump will deliver a flow rate of 52 litres per second while using only 1L of diesel per hour, resulting in a running time of 180 hours or 7 days straight without the need to refuel. The 6” pump is also highly efficient, using only 2.67L of diesel per hour, equating to 80 hours or 3 days running time. These fuel savings equated to €100 per day per pump.
The pumps supplied to PJ Careys on these projects were excellent for working in a remote bog environment. The reliability and especially the economy of fuel used, was very beneficial to Careys during the wind farm projects both in terms of actual running cost and the minimal maintenance required. We won’t hesitate to use Groundforce pumps on future projects.
Joe McCann, Project Construction Manager - PJ Careys