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Deephams: Thames Water's defining moment

Early contractor involvement is seen by Thames Water as the key to its plan to upgrade sewage treatment standards at its Deephams works in north London.

Water firm Thames Water was this week preparing to pursue its first early contractor involvement (ECI) project. It will enable the company to deliver a major new sewage treatment upgrade.

Thames Water capital delivery director Lawrence Gosden explains that the major challenge of rebuilding, and possibly moving, one of the country’s largest sewage treatment plants serving a population of almost 1M has led it to the use of the ECI model It is hoped this will help deliver the scheme on time, safely and to budget.

£270M investment

An estimated £270M is to be spent on Deephams Sewage Treatment Works in Edmonton, north London with the primary aims of improving water quality and keeping up with population growth.

The plant is already undergoing a £50M makeover to be completed in December. This aims to deal with excess stormwater inflows. The plant receives 209,000m3 of sewage on an average dry day but this can rise to in excess of 1.3M.m3 - enough to fill 520 Olympic swimming pools - after heavy downpours.

“We’ve said ‘let’s get the experts in and engage with them up front.”

Lawrence Gosden, Thames Water

A combination of building new storm tanks and fitting new self-cleaning devices as well as rebuilding the plant’s inlet that brings in the sewage plans to make this more manageable.

But the work must not stop there and now a major new scheme, which has been approved by regulator Ofwat, is being planned principally because of new stricter national and European water quality standards (see box).

These centre on the quality of the discharged water that goes into Salmon’s Brook, which in turn feeds into the River Lee - which must attain better water quality standards in the future.

National Policy Statement

The Deephams works’ need for “significant new treatment facilities” is also identified as one of the very few major schemes in the draft Waste Water National Policy Statement (NPS), which is expected to be designated this year.

But details of how exactly to meet the varied challenges of the project have yet to be determined and this is where the ECI model comes in.

An upgrade will be needed for the primary, secondary and tertiary stages of the sewage treatment process at Deephams but a number of options are being explored including whether it is best to build on the existing, congested and urban site - while the existing plant is kept operational - or on a new site.

“We want the project to deliver the very best value for our customers’ money”

Lawrence Gosden, Thames Water

In all options, the existing inlet pumping station, inlet works, storm tanks, sludge treatment process and effluent discharge location will remain on the current site.

But if relocation is chosen, treated effluent will have to be transferred back to the existing Deephams site.

Adding to the challenges is a tight timeframe - the new facility must be running by March 2017 and realistically the firm expects to submit a planning application no sooner than 2013/14, all of which means that, depending on which option is chosen, a construction start date of 2015 is hoped for.

Innovative thinking

“We need a big piece of innovative thinking,” says Gosden. “We’ve said ‘let’s get the experts in and engage with them up front’.”

“Rather than simply telling them what to do, we are asking the would-be contractor to help define the project, to help design and plan the work, and then deliver it to the highest standards.”

The Deephams Challenge

Deephams serves a population of 885,000 across a catchment that includes nine London boroughs. This is forecast to rise to 941,000 by 2026.

The works was built in 1877 and updated in the 1950s and 1960s. The new £270M Deephams project, while separate, aligns with Thames Water’s London Tideway Improvements scheme, comprising a £675M upgrade of five other main sewage works, and building the £635M Lee Tunnel sewer and the planned £4.1bn Thames Tunnel supersewer.

It’s not an entirely novel approach for Thames Water - Gosden says he is a “massive fan” of getting contractors in at the earliest stage and Thames Water already has four large consortiums it appointed at the beginning of regulatory period AMP5 in 2010, on a framework to carry out £5bn worth of routine work.

But this is the first full scale formal ECI arrangement it has sought and the plan is not to bias the options available but learn from industry about how it can tackle the challenge.

Gosden says one of the more likely options is to construct on the existing site - but this will be one that requires interested parties to draw on best practice. And Gosden expects that prefabrication can play a large role.

Offsite production

“One way of innovating will be by building as much as possible in factories - off site production is significantly safer and efficient,” he says.

Rather than approach the scheme with reticence over the scale of the challenge, Gosden is keen that it allows the industry to show what it can do.

He says “there’s nothing like” a grand challenge to get people working in a partnering way.

After it holds a supplier day later this month Thames Water is expecting a consultant/contractor venture to come up with the option which will best enable it to begin procurement in the spring.

Gosden also hopes that enthusiasm is displayed not only by its current supply chain but also new partners that are “the best that are out there”.

He stresses that the project is proceeding ahead of planning permission, and in places, policy. He says it is vital to demonstrate that it will be value for money so that Thames can secure funding.

Initial views on the preferred solution will be subject to a full public consultation - set to begin sometime this year.

This will take account of views from the relevant local authorities, statutory consultees, local residents and other stakeholders. Phase two would follow on in 2013.

Nationally significant

While the relevant NPS is also due to be designated this year, until it is, it is not yet entirely certain whether the scheme will achieve the status of nationally significant infrastructure - even though the draft NPS indicates it is.

If it does its planning application will be handled by the rebranded Infrastructure Planning Commission.

“The size of the project, its importance nationally and locally, and the need for it to bring significant environmental improvements in a heavily built-up area of the capital, makes ECI the obvious option,” says Gosden.

“Above all, we want the project to deliver the very best value for our customers’ money, and we also want it to be a leading example of safe construction.”


Legal background

The new development must

  • Comply with European Union Urban Waste Water Treatment, Water Framework and Freshwater Fish directives
  • Comply with new Environment Agency discharge consents to be instigated from March 2017
  • Meet already-imposed new consent limits on phosphorous levels, that require a 66% reduction in suspended solids, a 50% reduction in biochemical oxygen demand and a 66% reduction in ammonia.

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