Water and Effluent Treatment Magazine
Issue link: https://read.utilityweek.co.uk/i/283328
10 WET NEWS March 2014 Peacehaven's all-galvanized, steel framed structure is covered by a parabolic roof that rises to 18m and dips to 14m above ground. The 18,000m2 of roof is covered with a specially grown turf made up of downland grasses Peacehaven: on budget, on time and under cover • Southern Water's Peacehaven wastewater treatment works is an engineering delight, but is almost completely hidden from view. Dean Stiles reports. S outhern Water's Peacehav- en project, to meet Euro- pean environmental stand- ards on wastewater treatment, is the largest ever undertaken by the company. It was completed on time and within budget last year by 4Delivery (4D), a joint venture of Veolia Water, Costain and MWH. The project, delivered with an exemplary record for health and safety and community engagement, was no engineer- ing delight for many local resi- dents who mounted a fierce campaign to oppose it when, in 2003, Lower Hoddern Farm was proposed as the site for the works by Southern Water. It took six years to clear the planning threshold with two planning applications and a Public Inquiry before permis- sion was gained in 2009, allow- ing construction to start the fol- lowing year. Southern Water's team com- prising Mott MacDonald, as engineering consultant, RPS as environmental consultant and Savills as planning advisor han- dled site selection, feasibility and the planning process with a brief to find the best practical environmental option for the new scheme. "This project pre- sented numerous challenges finding innovative solutions to what is a unique and PROJECT SPECS • Building 11km of new sewer tunnel • Construction of two pumping stations, shafts, tunnels and connection to the existing sewage infrastructure • Construction of a wastewater treatment works, including a third pumping station • Establishing a sludge recycling centre • Building a 2.5km long sea outfall at Friars Bay ONSITE PEACEHAVEN multifaceted problem," says John Coates, engineer- ing governance manager for the project at Mott MacDonald. "Planning and environmental constraints in the Brighton and Hove area included being sur- rounded by an Area of Out- standing Natural Beauty, a pro- posed National Park, Sites of Special Scientific Interest, and a variety of conservation areas. "These constraints serve to heighten the environmental impact of development outside the urban areas and by so doing increase the pressure for devel- opment of brownfield sites within the city for which there already are competing develop- ment aspirations. The result of this is heightened local and national interest in the scheme." Ecological and archaeologi- cal surveys and clearance works were carried out in summer of 2009 and 4D started on site in the autumn of 2009, construct- ing an 11km sewer tunnel, three pumping stations, 17 sha›s, a wastewater treatment works, a sludge recycling centre, and a 2.5km sea outfall. There are three pumping sta- tion sha›s, ranging from 17 to 18m diameter and up to 46m deep, at Marine Drive, Brighton; Portobello Telscombe Cliffs; and Peacehaven Water Treatment Works to li› the wastewater allowing it to gravitate through the sewer tunnel to the WTW at Peacehaven. Marine Drive and Portobello pumping stations required con- struction of contiguous piled walls to provide support to the A259 while the sha› sinking works were carried out. "Over 150, 900mm diameter piles between 12 metres and 20 metres deep were installed to support the bulk excavations adjacent to the A259," said Richard Goodridge, construction man- ager with 4D. The sha›s were constructed using pre-cast concrete segmen- tal linings, installed using 'underpinning' techniques, fol- lowed by sprayed concrete lin- ing applied using hand nozzle techniques as well as a remote control spraying machine. "The deepest sha› on the project is the pumping station sha› at Marine Drive, with exca- vation to – 14.00 metres AoD, meaning the finished structure is 46m deep to invert. Generally excavation of all of the pumping station sha›s has been to levels below that of the existing ground water levels. Therefore extensive grout injection ground treatment and dewatering oper- ations were required across the sites," Goodridge says. Tunnels Two routes were considered for the transfer tunnel between Brighton Marina and the works at Peacehaven: a coastal route and an inland route. The coastal route was selected as it is more direct and better related to exist- ing sewerage infrastructure, Goodridge says. "The 9.13 kilometres of seg- mentally-lined transfer tunnel on the project was driven using Lovat tunnel-boring machines launched from sha›s at Peace- haven and at Ovingdean with reception sha›s at Marine Drive, Friars Bay and two at Portobello. The tunnels are 2.44m internal diameter constructed out of sin- gle pass trapezoidal segments. The segments are 175mm thick and are constructed utilising steel fibre reinforcement. "In addition, there are a number of shorter headings for "There is an immense sense of achievement and pride on site" Richard Price, director of capital delivery, Southern Water ►