This Spring marks a major milestone for engineers building a mega £300M wastewater treatment scheme in Sussex. Mark Hansford went to Peacehaven to find out more.
The coastline stretching east from Brighton to Peacehaven is unquestionably one of the most glorious sites in England, with the South Downs gently rolling down to meet the sheer white cliffs rising up from the sea.
It is a serene and tranquil place, yet one that right now hides a rather dirty secret - at the moment, wastewater from the area receives only basic treatment before being released into the sea through 1.8km long pipe.
As a result, this beautiful place is the only area in Sussex, and among the last in Europe, that fails to meet European standards for wastewater treatment.
Thankfully, that will change later this year. Southern Water and its delivery partner 4D - a consortium of Costain, MWH and Veolia Water - is nearing the end of a £300M scheme that will ensure that 95Ml of wastewater generated each day is treated to the highest standard before being released much further out into the English Channel.
But doing this has not been easy. Bear in mind that the main population centre - and generator of much of the wastewater - Brighton & Hove is very congested and nestles at the foot of the South Downs. Where could a site be found to house a treatment works? The best answer was Peacehaven, or more accurately, Lower Hoddern Farm, a greenfield site and a large, well-used public space separating Peacehaven from the Downs.
The technical challenge of moving the wastewater the 11km from Brighton to Peacehaven was clearly going to be a challenge. Indeed, what has been built is immense. This includes the 9km of 2.4m diameter bored tunnel to transfer the wastewater via two massive pumping stations; a vast treatment works and the 1.8km long pipe-jacked outfall tunnel.
But this is nothing compared to what was the challenge of placating incensed Peacehaven residents who saw their town as the dumping ground for Brighton’s sewage.
Nine years of protests against “Poohaven”, culminated in August 2008 with streams of abuse being hurled at councillors as East Sussex County Council’s planning committee voted by just four to three to proceed with the scheme. Demonstrations were organised across Peacehaven following the decision and action groups urged residents to stop paying their bills.
“I remember coming here in February 2009 and having to go incognito as it was all so sensitive”
Graham Sugrue, 4D
It was into this cauldron that 4D and its project manager Graham Sugrue walked in February 2009.
“From a civil engineering point of view it is an absolutely immense project,” says Sugrue, a Costain man through and through who has seen more than a thing or two in his time.
“But I remember coming here in February 2009 and walking across the site when it was just a field and having to go incognito in shorts and a T-shirt as it was all so sensitive. ‘Poohaven’ banners were everywhere. The perception at the time was of something very different to what has actually been built,” he says.
Now, just three years on, attitudes have changed, aided by an intensely proactive public relations effort from Southern Water’s public relations manager and project enthusiast Madeline Stoneman. More than 1,200 visitors have been shown around the sites.
“It’s pretty much a case of if people contact us, we will show them round,” says Stoneman - and the project has won two Gold Considerate Contractor awards.
But no amount of good PR would have won over the locals if the solution wasn’t a good one. And it is.
“From the structures we have put in with sympathetic design, to the construction planning to make the works as least disruptive to the project, it is absolutely immense,” says Sugrue.
It’s also rattled along at an incredible rate; so much so that many familiar with it over the years find it hard to believe it is nearing completion.
“I’ve been involved in this project since the first planning application was made in 1997,” notes MWH project director John Coates.
“People even tend to switch off when I mention it back in the office. But now, just three years after starting construction it is almost finished.”
Rain, snow and high winds
Things haven’t been plain sailing either. “We had a bad winter in 2009/10 with lots of rain, snow and high winds. It disrupted us a lot and we lost a lot of time and had to work doubly hard to recover that,” notes Sugrue.
“We did a lot of collaborative planning and that helped us get to where we are today,” he adds. Cost consultant Turner & Townsend also helped out here. It is client Southern Water’s cost and commercial advisor on the job. The firm was instrumental in getting all parties to agree to a reworking the contract last Spring resolving outstanding issues and creating a new target cost for the construction works - one that is actually down slightly from £225M to £223M.
“We had a bad winter in 2009/10 with lots of rain, snow and high winds. We lost a lot of time and had to work hard to recover that”
Graham Sugrue, 4D
“The weather, plus some significant procurement issues in the supply chain made 2010 a tough year for the project,” says Turner & Townsend project manager John Gunn.
“I joined the project in December 2010 and we spent six months working together on a supplemental agreement that tied up a lot of claims.
“We agreed a new target cost that wrapped up all the issues so that 2011 could become a smooth year and the contractor could just get on with the job.
“Without the agreement we would have spent a significant amount of time on target cost claims, which would have been distracting and not a good use of everybody’s time,” adds Gunn.
“This allowed the majority of people to keep their focus on delivery.”
Which is no bad thing, given the scale of the challenge.
The heart of the scheme is the new treatment works on the Lower Hoddern Farm site. The works is a sensitively designed steel framed beast which features the largest green roof in the UK. The design also saw the surrounding land shaped in such a way that the works is practically invisible from the east.
“It doesn’t actually look like a sewage treatment works,” says Sugrue.
But before the wastewater gets there it will have travelled for up to two hours by gravity from Brighton Marina where a new 11km long sewage tunnel connects with the existing network. This part of the scheme also had environmental considerations at the top of the agenda.
Two pumping stations
To avoid the tunnel getting too deep there are two pumping stations along the route. They will lift the wastewater approximately 16m vertically within a shaft before passing it into the next section of tunnel.
The first pumping station - in the middle of the A259 at Marine Drive - has been designed as a landmark building to provide a gateway into Brighton from the east. The domed roof has been covered in zinc, and the sweeping walls are formed by cast stone sets - a form of architectural concrete.
In contrast, the second pumping station, Portobello, is located on the clifftops at Telscombe and has been designed to blend into the landscape, maintaining the open views out to sea from Telscombe Tye.
Set into the cliff, the roof of the building will be grassed, and the brick wall running alongside the boundary of the site will be replaced with a more traditional brick and flint wall.
The varying topography means the depth of the shafts varies enormously. At Marine Drive the shaft is 46m deep, and at Telscombe the shaft is 34m deep. Eight more shafts ranging from 3m to 8m wide and 12m to 41m deep have also been built along the route to allow local sewer connections to be made.
Between the shafts are the tunnels along which the wastewater will flow. These have been excavated by four tunnel boring machines in six drives at a rate of up to 40m a day.
One Lovat 115 TBM was used to go from a launch shaft in Ovingdean 1.7km to Marine Drive and then 3.6km from Ovingdean to Portobello. A second Lovat 115 TBM was driven 2.7km from Peacehaven to Portobello and then 1km from Peacehaven to Friars Bay - the point at which the treated wastewater leaves land and is pumped out to sea.
This core section of tunnel was 2.4m in diameter, and due to the undulating landscape of valleys and hills along the route depth here varied from a modest 8m to a hefty 40m below ground level.
At the extreme ends of the scheme - from the Marine Drive shaft to the connection with the existing network at Brighton Marina and from Friars Bay out to sea - 1.8m diameter pipe-jacked TBMs were used.
The final TBM was recovered earlier this year, completing the tunnels in readiness for wastewater being divertedinto it and on to the new Wastewater Treatment Works in Peacehaven in the next few weeks.
Now, 4D is focused on commissioning the complex treatment process. Commissioning will take up to a year, such is the complexity of the plant (see box).
“We have very much broken the back on the civils side now,” says Sugrue.
Each process will be commissioned in turn, starting with the preliminary treatment, followed by primary and then secondary treatment.
Preliminary treatment will remove inorganic materials that cannot be treated such as sanitary products and grit washed into the sewers from the roads.
Primary treatment will remove organic matter suspended in the wastewater. Secondary treatment is a biological process that will remove bacteria before the wastewater is sent out to sea via the 2.5km long outfall.
The organic matter removed during primary treatment goes through an anaerobic digestion process before being dried, formed into pellets and spread on farmland as a soil conditioner.
All the processes are covered and any odours will be captured and passed to an odour control plant for treatment before the cleaned air is released from a stack.
Odour was a major issue during the protracted planning process, and Southern Water is spending approaching £7M on the most advanced odour extraction plant it could get its hands on.
“There just mustn’t be any odour,” says Sugrue. “Residents don’t want to smell the plant, they don’t want to see it, and they don’t want to hear it. We must deliver on our promises.”