Proprietary brace gives substantial clear opening during pumping station construction
Sponsored

Groundforce has supplied its new Super Mega Brace hydraulic frame system to Sorensen Civil Engineering, who along with their Joint Venture Partner, EPS, are undertaking a DBO (Design, Build, and Operate) project for Irish Water, in partnership with Cork County Council in Youghal.

With a population of around 7,000 the town of Youghal is currently served by a number of untreated foul sewer outfalls to the Blackwater estuary.  This project which is part of the wider Youghal Main Drainage Scheme, aims to augment and upgrade the wastewater management system in the town and provide a new wastewater treatment plant that will treat all of the towns foul flows and discharge the treated effluent to sea though a new marine outfall pipe.

Sorensen, along with specialist M&E partner EPS, was awarded the €12 million DBO contract in 2015. The construction element is two years and the operation contract runs for a further 20. The project is on course to achieve its completion date of January 2018.

A major element of the project is the design and construction of an upgrade to an existing underground reinforced concrete pumping station and associated building at Dunn’s Park. This pumping station is located in a residential area to the northern end of the town and it will function as the only feeder pumping station to the new 16,000PE wastewater treatment plant.

The upgrade works involve the construction of a large underground in-situ reinforced concrete tank next to the existing pumping station, as well as an extension to the existing pumping station building that will largely sit on top of the new 16m x 16m x 6.5m deep tank. There are existing large diameter incoming and outgoing pipes that require diverting as part of the works.

The pumping station site is low-lying and susceptible to flooding, with challenging ground conditions comprising slightly sandy gravely silt and the ground water table at 1m below ground level.

Sorensen approached Groundforce to explore options for temporary support of the cofferdam as given the depth of the excavation, silty ground conditions and high water table, a cantilever sheet pile solution was not feasible.

Groundforce proposed two options of temporary support – 1) a heavy-duty mega brace hydraulic frame with 150-tonne MP150 hydraulic prop knee braces and 2) the super mega brace hydraulic frame, believed to be the largest proprietary system available in the market with a fabricated section of 575mm x 622mm.

The first option was lighter and less expensive but would have resulted in the knee braces clashing with the formwork during the construction of the tank walls due to the restricted nature of the site. Subsequently, Sorensen opted for the Super Mega brace which allowed them to excavate and pour the walls of the tank without obstruction.

Sorensen director John Wallace said: “The main challenge facing Sorensen Civil Engineering was constructing a cofferdam that would safely retain the ground to a depth of 6.5m in extremely difficult ground conditions, surrounded by a network of existing services whilst maintaining an opening of 18m x 18m.

The chosen solution involving the Groundforce Super Mega brace allowed this clear uninterrupted opening which in turn permitted us to complete the steel and concrete works in a safe and timely manner.”

”Groundforce General Manager Joseph Lenihan comments: “We were delighted to get involved with Sorensen on this challenging element of the project and with Irish Water now starting to tackle deficiencies in the country’s water and waste-water treatment infrastructure, deep tank construction like this will become more common”.

“This is only the second time that this brace has been used in Ireland since coming to the market in 2015 but with clear opening-potential of up to 23m x 23m, I believe this system will become more popular”.

http://www.engineersjournal.ie/wp-content/uploads/2017/08/groundforce-site.pnghttp://www.engineersjournal.ie/wp-content/uploads/2017/08/groundforce-site-300x300.pngJames HarringtonSponsored
Groundforce has supplied its new Super Mega Brace hydraulic frame system to Sorensen Civil Engineering, who along with their Joint Venture Partner, EPS, are undertaking a DBO (Design, Build, and Operate) project for Irish Water, in partnership with Cork County Council in Youghal. With a population of around 7,000 the...