Give Peacehaven a chance
It has taken well over a decade for Southern Water to get to work on a new WwTW for Brighton and Hove. Karma Ockenden finds out that the engineering challenge, while enormous, is only part of the story
Southern Water is now part-way through a project that many may have thought would never get off the ground – putting sophisticated arrangements in place for dealing with wastewater from the Brighton and Hove area.
For it was way back in 1997 that the company first applied for permission to upgrade its Portobello treatment works, which simply screens wastewater to remove debris and grit before pumping the effluent 1.8km out to sea.
Planning permission was denied, and there started a wrangle that in its troubled history has included a rejected Portobello appeal by Southern Water and a European Court of Justice judgment against the UK for Brighton and Hove’s failure to meet some of the standards demanded by the Urban Wastewater Treatment Directive (UWWTD).
Southern realised there was a pressing need to act, so started looking at alternatives to the Portobello upgrade. Some 66 sites were originally considered. This was narrowed down to eight, and then one.
The chosen site for the new wastewater treatment plant (WwTP), at Lower Hoddern Farm in Peacehaven, was “the least worst option”, says project PR manager Madeline Stoneman. It was spacious; met the local waste plan objectives; satisfied the planning inspector on odour, noise, vibration and environmental impact; and did not pose too great a problem on either the traffic or land loss fronts.
All that said, it has taken a huge stakeholder liaison effort on Southern’s part to get the plan off the drawing board. Opposition was fierce in some quarters – from a hardcore of local activists, known as PROUD (Peacehaven Residents Opposed to Urban Development), to East Sussex County Council, which fought the plan all the way until Southern finally secured permission though judicial review last year.
Consequently everything from work scheduling to the appearance of the plant has been considered and reconsidered to take community concerns into account. Particular effort has gone into ensuring that project sites, once reinstated post construction, are as easy on the eye as possible.
Under way at last, though, the £300M on-budget project, known as Cleaner Seas for Sussex, is mammoth. Its infrastructure element involves the construction of an 11km, 2.4m diameter tunnel, which will run at depths ranging from 8-40m.
This will transfer flows from Brighton and surrounding areas to the new plant, and cleaned wastewater out to sea via a 2.5km pipe off Friars Bay. Along the tunnel route, shafts, or access holes, are being dug at Brighton Marina, Marine Gate, Roedean Way, Ovingdean, Rottingdean, Saltdean and Friars Bay. These range in width from 3m to 8m, and in depth from 11m to 41m. Manhole covers will be all that will remain of most of these sites post construction.
Two new underground pumping stations are also being built on route: one at Marine Drive, in a shaft 17m wide by 46m deep, to lift the flow 16m vertically; the other at the existing Portobello treatment works site, in a shaft 18m wide by 34m deep, to lift the flow 13m vertically.
Rob Smith, general foreman at Portobello, explains that the existing WwTP there is remaining operational until the Peacehaven plant is commissioned.
The Portobello station will have a grassed roof, and has been designed to maintain sea views, while the Marine Drive station will be housed under a domed structure.
The main section of tunnel is being built using two hired tunnel-boring machines (TBMs), named Alice and Hollyblue by schoolchildren. Alice is based at Ovingdean and will be tunnelling from there west to Marine Drive and east to Portobello.
Hollyblue is based at Peacehaven and will go west to Portobello and south east to Friars Bay. These create the tunnel using a rotating cutting wheel at the front, with the tunnel wall sections installed behind the wheel as it passes through.
The shorter, smaller (1.8m diameter) sections of tunnel (west from Marine Gate to Brighton Marina and east to Marine Drive; and a short section at Friars Bay) are being pipejacked. Here pipe sections are placed into the hole created by the cutting head and pressure applied to them to push the cutting head forwards.
Various of the shafts and tunnel sections are being built simultaneously to speed up the build. The earliest work started in June, and all construction work is scheduled for completion in 2012, although some parts will be finished much earlier.
The TBMs are expected to progress at around 20m a day, and at the end of September, Alice had tunneled some 850m and Hollyblue 300m. The Peacehaven plant itself will be capable of treating 95Ml of wastewater. Employing around 300 workers, the build is well under way, and the plant due to be fully operational in 2013.
On entering the plant, flows will be screened as at the existing Portobello works, but will then go through two further treatment stages before being pumped out to sea.
At the primary treatment stage, solid waste will be removed in settlement tanks; the effluent will then undergo biological treatment in one of ten biological aerated flooded filter cells to remove remaining organic pollutants. Southern has left space on site for a third stage of treatment, should this be required in future. As it stands though, the wastewater discharged at Friars Bay will meet all UWWTD standards.
Sludge will be collected at each treatment stage, digested and dried on site before being granulated and bagged for use on land. Biogas created during the process will be channeled to new 1MW combined heat and power plant, generating electricity for site use as well as heat for the treatment process.
With a perimeter of around 4km, the construction site is vast, although once reinstated, much of the land will be returned to agriculture and a new public recreation area built, at Southern’s expense, including landscaping and sports facilities. The plant itself will have an 18,000m2 grass roof and be further screened from view by planting.
At Peacehaven, community liaison is extensive and ongoing. Both public and specialist feedback has been taken into account throughout the design and build. Even some very hostile opponents seem to have been turned around.
Southern should perhaps consider its Cleaner Seas project as great a public relations challenge as an engineering one.
© Faversham House Ltd 2023 edie news articles may be copied or forwarded for individual use only. No other reproduction or distribution is permitted without prior written consent.