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Two Thames Water projects along the A346 will enhance the River Kennet valley


Work underway in the River Og water meadowsWork underway in the River Og water meadowsSeveral of Marlborough News Online's readers have asked us to sort out some  confusion about the works being carried out for Thames Water along the A346 between Marlborough and Chiseldon. There are two separate sites working on entirely separate projects.

As you drive north out of Marlborough, down Port Hill and past the golf club entrance, you come to Bay Bridges.  On the right of the road, just opposite the lay-by with The Full English café and with occasional hold ups as traffic lights allow large trucks to turn off the road, you can see the base for a major Thames Water engineering project.

The Bay Bridges works are to install a new pumped sewer into the Marlborough sewage treatment works.  This will go below the surface, through the water meadows alongside the River Og.  The new pipes will lessen the risk of sewage leaking into the river.

Work on this contract was suspended for several weeks so that the route of the new pipe could be checked for unexploded ordnance. This followed the chance discovery in September last year by people searching for treasure with metal detectors of an unexploded grenade.  

This involved closing the A346 while the bomb squad detonated the grenade.

Following this incident, research revealed the water meadows had been used during the Second World War as a firing range for American servicemen from the hospital on Marlborough common.  Live munitions were used in tests to see if they were fit to return to the front line in Europe.

The route for the sewer pipe was surveyed using ground radar equipment, but no unexploded munitions were found.

Pipes being joined togetherPipes being joined together

Thames Water's contractors on this project are using very sophisticated directional drilling technology, which will minimise the environmental impact of laying the pipe. They are also going to great lengths to ensure that they don't add sediment into the River Og, or disturb the wet grassland and reeds.

Their ecology report for this project recognises the sensitivity of the site in relation to the River Kennet SSSI, and they method they are using (directional drilling) is an expensive option selected to ensure minimal disruption to the important habitats.

This project is now on schedule to be finished by Christmas.

Further north along the A346, other contractors for Thames Water are laying a pipeline parallel with the road near Chisledon.  This is part of Thames Water's scheme to bring water to 30,000 homes in south Swindon from the Farmoor Reservoir in Oxfordshire - which takes its water from the River Thames.

The pipeline near Chiseldon - beside the A346The pipeline near Chiseldon - beside the A346[Click on photos to enlarge them][Click on photos to enlarge them]

This 18 kilometre pipeline costing about £25 million will mean that Thames Water can stop extracting water at Ogbourne (from the River Og) and reduce their extraction at Axford (from the River Kennet.)  This extraction has been having a detrimental impact on the River Kennet - a listed Site of Special Scientific Interest (SSSI).

The new mains will run from Blunsdon Reservoir, pass through the Honda car plant, go under the main London-Bristol railway and under the M4 - see map below.  Blunsdon Reservoir was built in the 1930s and a new pipeline linking to Farmoor Reservoir was completed in 2005.

The 4.8 kilometre stretch of 500 millimetre pipeline being laid through farmland beside the A346 near Chiseldon will take the water from the M4 culvert to the two Whitefield Hill Reservoirs on the hill above and to the east of the A346, from where it can feed into existing delivery networks.  

This pipeline will not come any closer to Marlborough than Whitefield Hill. The project is due to be complete by the end of 2016.

Action for the River Kennet has been campaigning for a major reduction in water extraction from the Kennet valley for twenty years.  ARK's Director, Charlotte Hitchmough, told Marlborough News Online: "We are delighted to see work underway on the ground and that the project is going to schedule."

Environment Agency's River Kennet level measurement at Marlborough -the small increases followed the weekend rainEnvironment Agency's River Kennet level measurement at Marlborough -the small increases followed the weekend rainAs it happens the level of the River Kennet at Marlborough is currently very low. Ground water levels are slightly below average for the time of year due to lack of rain - in many years October has seen the River's lowest levels.  

There have been three months of below average rainfall.  But ARK says the level is following a normal pattern for dry years.

If you are in any doubt about the different projects, just remember sewer pipes are black and water pipes are blue. 

It is important to know the difference  - just like knowing the difference between brown (live) and blue (neutral) wires in electric cable: do not touch brown - do not drink from black.

The section currently being laid near Chiseldon is marked in green.The section currently being laid near Chiseldon is marked in green.




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