Questions

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Questions about the upgrade

We have started work on a major upgrade to our Deephams Sewage Works in Edmonton.

We need to develop an improved sewage treatment process, while continuing to treat the 209,000 tonnes of sewage that arrives at the works each day. This can increase to over 1.3 million tonnes during heavy rainfall – enough to fill 520 Olympic swimming pools.

Following feedback from the first phase of consultation in 2012, we are upgrading the treatment works within the boundaries of the existing Deephams Sewage Works site.

  • To meet new wastewater quality standards set by the Environment Agency
  • To replace the existing treatment plant that is becoming old and worn out
  • To cater for predicted population growth in the area
  • To cope with weather variations that are predicted to occur due to climate change
  • To significantly reduce the odour from the works, at a reasonable cost to all of our wastewater customers

The upgrade is likely to take approximately three years to construct, we received planning permission in March 2015 and the main construction work started in July 2015.

The new wastewater treatment standards set by the Environment Agency will be met by March 2017 and we plan to finish building the upgrade and tidying up the site by late 2018.

We have to keep the sewage works running throughout the construction period to continue to meet the existing standards set by the Environment Agency. This means we have to build the upgrade in a number of phases.

Visit the How we will build the upgrade page to find what we will be doing during each phase of construction.

No. The upgraded sewage works will remain within the boundary of the current site and the tanks and equipment used to treat the sewage will actually take up less space on the site than they do currently.

The upgraded sewage works has been designed to cope with the greater amount of sewage produced by the predicted increase in population in the local area, but the works will not get any bigger than it is now.

The total cost of designing and building the Deephams Sewage Works Upgrade will be around £250m and will be paid for through the bills of our 15 million wastewater customers.

As with all the costs of providing high quality tap water for our customers and removing and treating their sewage, the cost of the upgrade will be reflected in our customers’ bills.

Similar upgrades to our other sewage works in have also been funded in this way, with the costs of the work being spread across all of our customers’ bills, wherever they live in our region.

We have put up noise reducing fencing and some piles of earth called bunds to stop any noise travelling too far. We write to local residents before starting any particularly noisy work or work that could cause strong vibrations.

We are using low-noise equipment where practical and have designed the upgrade so that any particularly noisy activities are moved to parts of the site that are further away from our neighbours.

Our aim is to limit dust and dirt leaving the site to a minimum.

We prevent dust blowing outside the site by spraying dusty areas or equipment with water. All lorries travelling to and from the site are covered.

We also wash the wheels of vehicles leaving the site to stop dirt and mud being left on local roads.

Our normal working hours will be between 7am and 7pm, Monday to Saturday, and we will not start any noisy work until after 8am or carry it on after 7pm during the week, or after 5pm on Saturdays.

If for any reason we have to work outside of these times, we will let local residents know in advance. We need to seek permission from the council before we do this.

We will make sure that any large vehicles travelling to and from the site, only use local residential roads when no alternative exists, for example when delivering from local industrial estates.

Otherwise, all heavy vehicles will use more major roads such as the A1055 Meridian Way and the A406 (North Circular).

We submitted our planning application for permission to build the upgrade to the London Borough of Enfield in June 2014. We were granted permission with some reasonable conditions in February 2015.

Work on the upgrade started in July 2015.

Visit our Getting planning permission page to find out more about our planning application for the upgrade.

Questions about odour

We have carried out a number of improvements since 2010 to reduce the smell from the works and local residents have told us that they have noticed an improvement.

We want to do more, so achieving a much more significant reduction in odour is a priority in our plans for the upgrade.

We plan to spend around £24m on measures to control the odour produced by the smelliest parts of the works.

This will involve covering equipment and tanks and installing equipment to capture and clean odorous air.

Visit the Odour page to find out more about our plans to significantly reduce odour.

We will never be able to guarantee that any sewage treatment works will be completely free from odour.

We want to reduce odour as much as we can, by focusing our improvements on the smelliest parts of the works, at a reasonable cost to all of our wastewater customers.

As part of the process to choose the best site for the upgrade, we carefully assessed 22 potential sites within an area approximately 3km from the existing sewage works site.

None of these sites were as suitable as the current Deephams Sewage Works site for a number of reasons. The site has been used for the treatment of sewage for several decades and all the existing sewers in the surrounding area currently drain to it.

The Environment Agency requires the treated wastewater from the current and upgraded sewage works to flow into the Salmon’s Brook to maintain the river level. Upgrading the existing Deephams Sewage Works site will avoid the cost of pumping the sewage, treated wastewater and sludge from the existing site to any new site and back again.

Taking all the feedback from the phase 1 public consultation into account, the existing site remained the best option for building the upgrade and so we confirmed it as our proposed site.

Sewage can give off odour when it is treated, or moved around during the treatment process.

Although it is mainly water, sewage contains polluting materials that produce gases when they are treated or turn septic.

If the treatment process takes place in tanks that are open to the air, these gases can be released into the air and cause odour.

The amount of odour from a sewage treatment works depends on a range of issues including what is in the sewage, how long it takes to arrive at the sewage works, how it is treated, the direction and strength of the wind and how warm the weather is (sewage can smell more on hot days). We have no control over many of these issues.