Frequently asked questions

This project will increase our ability to move water around the capital but will not have any impact on the amount of water that is treated.

The total funding agreed by Ofwat for the two extensions of this project is £90million.

The funding for this programme has been agreed with our regulator, Ofwat, and will be funded through the increases in bills for 2005 to 2010.

There will be two extensions - one north and one south of the River Thames.

The north extension will be from Stoke Newington to our pumping station at New River Head.

The southern extension will be from our site at Brixton to our service reservoir at Honor Oak.

The route has been chosen following analysis of the results of surveying and investigations along the proposed routes.

Due to relatively high housing development density, the tunnel will pass below a number of residential/commercial properties.

Wherever possible, we will drive the tunnel below 'open' ground or below public highways.

We carried out the ground investigations using boreholes.

These provided information about soil types.

Further studies were undertaken to confirm location of underground services and the presence of deep foundations.

Using this information we determined the final routes of the tunnels.

Construction of the tunnel extensions is expected to start on site by late 2006 / early 2007.

The tunnel works will take two to three years to complete.

We will be carrying out communications with customers, the local and regional authorities, including statutory and non- statutory agencies, throughout the project.

This may include leaflets, meetings, drop-in sessions, letter drops and website updates.

The Tunnels will, on average, be 45 metres (approx 150 ft) below ground level.

Both tunnels will be approximately 5km long.

We will be using proven tunnelling techniques.

We completed the construction of the Tunnel Ring in 1995, and will be drawing on the same technologies and the experiences gained previously.

The only visible works at ground level will be the access shafts for each tunnel.

As a minimum requirement, tunnel shafts will be required at our operational sites at Brixton, Honor Oak and Stoke Newington.

There will be some noticeable noise at the access shaft sites but not from the tunnelling.

Traffic noise may increase but this will be restricted to the shaft sites only.

There will be no noticeable vibration due to the considerable depth of the machine.

Yes.

While constructing the tunnel we want to make full use of the tunnelling machine.

Not only will this make the best use of the machine and get the work completed as quickly as possible.

Tunnelling machines and techniques are very expensive - to leave them idle once a job has started would not be efficient.

The River Effra is a covered river which forms part of the south London drainage system.

It rises near Crystal Palace and passes through Norwood, Dulwich, Herne Hill, Brockwell Park, Brixton and Kennington before discharging into the River Thames by Vauxhall Bridge.

The tunnelling works will be approximately 40m (or 130 ft) below ground level as they cross below the River Effra Storm Relief Sewer.

Our engineers are aware of the river and confirm sufficient vertical separation between the culverted section of the river and the tunnel.

The works will not effect the river or increase the risk of surface water flooding.

The original Ring Main crosses under the River Thames eight times.

We do recognise that this will be a major concern to customers above the tunnel route.

From previous experience we do not expect any damage-either immediate or subsequent to the tunnel's construction.

We have had no complaints of damage caused by previous construction of the Ring Main.

To allay some of the concerns of those residents above and immediately adjacent to the tunnel's route, we will be offering condition surveys.

This will give a statement of the condition of the property prior to tunnelling and will be given to the resident.

In line with Paragraph 20 of our Code of Practice we will provide a full schedule of condition of your property free of charge.

Therefore, we would not wish to pay for another survey undertaken by another agent.

Paragraph 19 of our Code of Practice provides owners with the ability to seek professional assistance and the payment of fees but only in circumstances where a successful claim has been settled.

Notwithstanding the above and to reassure you, our Agents Messrs Bruton Knowles will discuss any aspects of a survey with you.

Spoil will be removed from the tunnel via the tunnel access shaft.

As a minimum requirement, tunnel shafts will be required at Brixton, Honor Oak, Stoke Newington and New River Head.

Excavated material will be brought to the ground at Honor Oak and Stoke Newington and then removed by lorry.

Vehicles movements will be limited to normal site working hours, therefore, some stockpiling of spoil may be required at the shaft sites.

The works are part of phased development of the Thames Water Ring Main. Further development work is planned for 10 to 15 years time, in accordance with Thames Water Ring Main operating strategy up to 2025.

Our Code of Practice mentions that if water pipes have less than 900 mm of cover, then we will tell you the exact depth and location to ensure their protection.

It also requires property owners and occupiers to seek our express permission if any activity risks damaging our network.

The Ring Main is approximately 45 metres below London and so building extensions to residential homes is unlikely to create such a risk.

However, more extensive works such as the construction of deep foundations using piling, may risk damage to the Ring Main and permission should be sought.