Project Summary
The Galway Untreated Agglomeration Study (UTAS) aimed to address the discharge of untreated and partially treated wastewater at four sites across County Galway. This contract focused on the delivery of wastewater treatment infrastructure in An Spidéal and Ahascragh, including the construction of a new wastewater treatment plant (WWTP) in Spiddal and the upgrade of existing facilities in Ahascragh. The project eliminated raw wastewater discharges into the environment and improved compliance with European environmental directives. A one-year operations and maintenance period was included.
Project Description
In An Spidéal, a completely new WWTP was delivered to serve a population equivalent (PE) of 1,000. A new terminal pumping station was constructed next to the existing Craft Village, redirecting wastewater from the local gravity sewer system. A rising main was installed to transfer flows to the new WWTP, located at the former Útarás na Gaeltachta treatment site. The WWTP comprises preliminary screening, grit removal, primary and secondary settlement tanks, three rotating biological contactors (RBCs), sludge storage, and odour control. A high-level stormwater overflow was connected to the existing marine outfall. Redundant assets were decommissioned and extensive site works, including surfacing, fencing, and landscaping, were completed. A new SCADA system was installed, and provision was made for future UV treatment.
At Ahascragh, the existing WWTP was upgraded to provide secondary treatment for a 470 PE. Works included construction of a new wet well, a stormwater storage tank, and a new primary settlement tank to replace the old Imhoff tank. Two RBCs and a secondary settlement tank were added, as well as a new sludge holding tank. The Combined Sewer Overflow (CSO) was modified to eliminate overflows, and the outlet pipe to the main pumping station was upsized. A screened stormwater overflow to the Mill Stream was installed. A new SCADA system was integrated and redundant infrastructure removed. Final works included surfacing, fencing, and landscaping.
Scope of Works
The works included:
- Design, construction, and commissioning of new WWTP in Spiddal (1,000 PE).
- Upgrade of WWTP in Ahascragh to secondary treatment standard (470 PE).
- New terminal pumping station and rising main in Spiddal.
- Wet wells, stormwater tanks, RBC units, sludge holding tanks at both sites.
- SCADA, instrumentation, sampling and telemetry systems.
- Temporary works for deep excavations in difficult ground conditions.
- Pipe laying in public roads with traffic management.
- One-year operation and maintenance contract.
Technical Highlights
- Deep excavations completed in challenging geological conditions: rock removal in Spiddal and high water tables in Ahascragh.
- Trench excavations on the R336 completed under live traffic conditions with a high standard of traffic management.
- Installation of major pipeline infrastructure, including a 100mm rising main through the Craft Village.
- Control buildings, toilet blocks and above-ground odour control units constructed on constrained sites.
- Instrumentation limited to level and flow monitoring due to the absence of chemical dosing systems.
- Lifting operations for RBCs and precast tanks executed using a 200T mobile crane.
Added Value
- Optimised design by reducing the number of pumps, lowering long-term operational costs.
- Reduced footprint by replacing four smaller RBCs with three larger units in Spiddal.
- All design works completed in-house by Coffey.
Environmental and Community Measures
- Noise and vibration monitoring were continuously carried out during construction, particularly during rock-breaking activities, to protect nearby properties and sensitive locations.
- Real-time noise alerts were issued to site personnel by phone and email when levels approached allowable limits.
- Vibration monitors were installed at five adjacent properties to track and control construction impact.
- High groundwater levels during excavation were managed through continuous monitoring and the implementation of dewatering measures, including silt bags, baffled settlement tanks, and straw filtration.
- Water from dewatering activities was tested daily before being discharged to ensure environmental compliance.
- A bat specialist was engaged prior to tree-felling works to ensure wildlife protection measures were followed.
- The project manager met with local stakeholders before the works commenced, outlining the scope and providing key contact information.
- Regular email updates were issued to residents to inform them of construction progress and planned disruptions.
- Construction activities were coordinated with the Ros na Rún film set, a local primary school, and a music recording studio to minimise impact:
• Rock-breaking was paused during outdoor filming.
• Break times were aligned with schoolyard hours.
• Recording sessions were scheduled around quieter site operations. - A WhatsApp group was created to facilitate real-time communication with local stakeholders and respond quickly to any concerns.
To learn more about Coffey’s work in water and wastewater management, or to discuss future opportunities, please contact us at 091 844356 or info@coffeygroup.com.
