SWELL PROJECT
SWELL - STRABANEWWTW
Crane lifts the last 18m long screw pump into place. Installation of the third a d final 18m-long screw pump at Strabane.
Screw pumps.
Pictured l-r (pre-covid restrictions): Bob McGarvey, NI Water SWELL project manager; Aidan Diamond, BSG Contracts Manager and Pahvai Raveenthiran, McAdam Design following the installation of the three 24-tonne screw pumps at Strabane.
STRABANE WWTW IS LOCATED TO THE NORTH-WESTERN EDGE OF THE TOWN AND HAS BEEN IN OPERATION SINCE 1974... STRABANEWASTEWATER TREATMENTWORKS
T he existing Strabane WwTWwas upgraded in 2004 to serve a design population equivalent of 38,000, with treated effluent being discharged to the River Foyle. Northern Ireland Water has undertaken continued investment in maintaining the site to achieve discharge compliance levels. However, with assets approaching the end of their design lives, and more recently, increased flows arriving at Strabane WwTW causing regular flooding of the inlet screen chamber, the plant required an upgrade. During significant storm events, flooding at the inlet screens can result in overtopping/bypassing of the fine screens and inlet pumping station and ultimately can lead to the discharge of wastewater via the storm tanks to the adjacent River Foyle. A detailed analysis of the catchment conducted for the SWELL project estimated that the existing works received load from a population equivalent of 24,806, reflecting a downturn in trade within the town in recent years. This means that, in comparison to its original design capacity, Strabane WwTWwas biologically underloaded. The plant remained in satisfactory condition and generally capable of achieving its current consent requirements for the quality of
treated effluent discharged to the River Foyle. However, the inlet chamber fine screens had reached the end of their useful life and no longer met current Water Industry specifications and standards. The upgrade at Strabane included the construction of a new inlet reception chamber with new screw pumps to lift storm flows to the existing preliminary treatment works. This solution provides Strabane WwTWwith the ability to better deal with storm events, making it more resilient to climate change impacts and providing additional protection to the surrounding environment. CONTRACTOR BSG Civil Engineering was responsible for the design, construction (civil and MEICA), commissioning and operation of the upgrade. This complex project came with some major challenges such as keeping the existing works operating and compliant while building the new inlet works. “This was achieved by the installation of 900mm DI diversion pipework and manholes,” explained Aidan Diamond, Project Manager for BSG Engineering, “that allowed for isolation of the existing reinforced concrete structure so that a new structure for the screw pumps could be installed offline while all flows
were diverted away.” Due to their length, the 18m screw pumps were classed as abnormal loads and needed to be delivered to the site from Dublin Port before 6am in the morning. Likewise, due to logistics issues and Strabane being a busy sludge import facility, careful planning had to take place to allow for full installation by 12 noon on the same day as delivery.
Commenting on the completed project, Aidan said, “BSG was
delighted to have the opportunity to share our wealth of knowledge and expertise at an early stage through the Early Contractor Involvement (ECI) process. This forward-thinking approach allowed BSG to feed into the design development phase, creating innovative 3D models that gave the client confidence to know that they were getting a robust, maintainable solution.”
PROJECTTEAM...
McAdam Design
Construction Consultancy Services
BSG Civil Engineering
Doran Consulting
www.northernbuilder.co.uk
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