£35Million Investment for Holyhead
Holyhead and the surrounding villages of Trearddur Bay, Four Mile Bridge, Valley and Caergeiliog are benefiting from a £35 million investment to provide a biological wastewater treatment works and sewerage improvements, which in turn deliver environmental benefits to the area. The work is helping to protect the area’s Blue Flag beach status and has removed constraints for further developments in the area.
Location
The new Holyhead Wastewater Treatment Works (WwTW) lies on the outskirts of the ferry port town of Holyhead – Anglesey’s largest town. The works is located between the Penrhos Industrial Estate and Anglesey Aluminium Smelting Plant and is bordered to the west by the main Holyhead to London railway line and the A55.
Work to construct the new WwTW and upgrade the area’s wastewater network was necessary to meet tighter environmental standards set out in the Urban Wastewater Treatment (England and Wales) Regulations 1994. These included removing unnecessary discharges from combined sewer overflows and ensuring any discharges did not have an adverse effect on coastal waters in the area. Dwr Cymru Welsh Water had until December 2005 to meet these requirements.
The previous wastewater system at Holyhead discharged untreated sewage through a series of short sea outfalls located at Morawelon, Turkey Shore, Waterside, Coastguard / Porth Sach and Porth y Felin. The wastewater network also contained combined sewer overflows, which had become increasingly ineffective in dealing with the increased demands placed on them – especially during storm weather conditions.
The wastewater treatment process
A collaborative partnering team was set up to identify the best way of meeting the regulatory requirements. Several treatment processes were considered for the WwTW, with the sequential batch reactor (SBR) being the preferred option. SBR would see the whole treatment process take place in one tank rather than in separate primary, secondary and final settlement tanks.
The location of the new WwTW caused concern amongst people living in the area. To alleviate these concerns, Dwr Cymru Welsh Water engaged in consultation with interested groups and looked at various locations for the works. Planning permission was secured in July 2003 and construction work began on 5th April 2004. The construction work took 14 months to complete, followed by a four-month commissioning period.
The new WwTW, serving a population of 23,000, now receives flows from outlying villages and Trearddur Bay via nine pumping stations and also from the Holyhead town network via seven pumping stations. Treated effluent passes through 5.7 km of land based outfall pipes before reaching a new marine outfall. This is located to the north west of Holyhead, some 890 metres offshore.
The outfall location was chosen after extensive marine studies and with agreement of the Environment Agency. Also during its construction a system of underwater marine pingers were used during its laying to help protect porpoises living off the coast.
The WwTW has a fully automatic operation and telemetry links to pumping station sites to enable rapid response when necessary. A standby generator, sized to cater for the power requirements for the whole of the proposed works, has been provided at the site.
Upgrade work to the area’s wastewater network involved the construction of 16 new pumping stations and associated stormwater storage facilities. 13.5 km of rising mains and 3km of gravity wastewater pipes were also laid to carry flows to the new WwTW.
Development
Dwr Cymru Welsh Water is committed to being a good and responsible neighbour and liaised extensively with various bodies to minimise the impact of the scheme. Countryside Council of Wales was consulted to protect species such as the great crested newt, badgers and water voles while Gwynedd Archaeological Trust provided advice on protecting a wide guage tram site, a 13th century listed structure at Four Mile Bridge and an ancient chapel / weel site. Environment Agency Wales, in their regulatory role, ensured waste regulations were adhered to during construction. Public exhibitions, school visits and project update notes were used to keep the local community informed.
The prevention of odours resulting from operation of the WwTW was central to the granting of the planning permission. To ensure compliance with tehse conditions, extensive odour prevention and odour control measures were incorporated in the project.
Galliford Try was the main contractor who engaged in a collaborative partnering approach, which included Imtech Process, ITT Sanitatire, EC Harris, Bullen Consultants, MWH, United Utilities Operational Services, William Hughes, Daniel Contractors, Mulcair, Land & Marine JV, EJ Kelly and Rock Blasting Engineering.
