Northern Ireland: Spencestown Inlet Works & Tullygarley WwTW

DAWSON-WAM Ltd. was appointed by Northern Ireland Water to construct a new inlet works comprising of a complex concrete structure, interconnecting pipework and integration of the new system into the existing infrastructure.

Spencestown is the main inlet works for Tullygarley WwTW, Ballymena.  It serves a population equivalent of 15,000 and receives normal flows in excess of 500 l/s up to 1,300 l/s in storm conditions.

This design and build scheme included:

• Accommodation works to divert existing storm overflow pipelines and electrical services to allow construction works to commence;
• Excavation and disposal on site, and landscaped into existing NIW land of mixed sub soils;
• Construction in reinforced concrete of large inlet works, storm overflow chamber and grit plant plus various minor plinths and slabs;
• 750mm dia. concrete outlet pipe which terminated within a live pumping station wet well.  Pipeline incorporated a flow measurement system and manholes.  Cable ducts were also laid at strategic positions to minimise below ground cable routes therefore improving access and maintenance.
• Approximately 3km of rising main, with associated final effluent pumping station, was laid from Tullygarley WwTW to Spencestown to provide the screens with final effluent (FE) wash water. 
• Installation also included some 100m of pipeline to be installed utilising directional drilling, HDD, to avoid construction through private gardens. 
• The provision of FE wash water removed the risk of a pressure drop on the existing potable water supply to the surrounding area.