Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

Thirsty work

Maundown - A new £25M water treatment works is the single biggest investment for Wessex Water over the next five years. Mark Hansford reports.

Somerset folk may have a well-earned reputation for voracious cider consumption, but 200,000 of them may soon be tempted back to a less potent thirst quencher when Wessex Water completes a £25M rebuild of its Maundown treatment works.

The new plant will provide additional treatment processes that will much improve the quality of local water supplies and reduce the impact of geosmin - a foul smelling naturally occurring compound produced by algal blooms.

Recent warm temperatures attributed to climate change have increased the occurrence of these blooms in the two reservoirs, and the existing 1960s water treatment plant is simply unable to cope. It is also struggling to keep up with an expanding population.

Client Wessex Water Services' project manager Mark Lloyds, explains: 'The old works has been extended and modied over many years, and is gradually coming to the end of its natural lifespan. We can no longer keep making piecemeal improvements to the site. It does not have the capacity to fully cope with the volume of water the reservoirs can provide, and treatment processes on site cannot treat the water to the latest drinking water quality standards.

'This scheme will make signicant improvements to the water supply for Taunton and the surrounding area, and will increase our capacity to supply water to the area in the future.' The new plant will have a capacity of 83Ml/d, signicantly up on the existing plant's 65Ml/d limit. It will also eradicate the impact of those pesky algal blooms.

A new contact tank will add disinfection before water is released into the supply network and a new sludge building will treat sludge resulting from the dissolved air otation process.

Wessex Water is running the project itself, through its in-house design and construction arm Wessex Engineering & Construction Services. It is acting as principal contractor, responsible for civil and structural construction and procurement.

FaberMaunsell subcontracted to do civils design, taking on Wessex's preliminary work.

'Wessex did preliminary design to 25%, but even that we changed a lot, ' explains FaberMaunsell project manager Steve Cole.

'It is a big project, a agship scheme, and the major thing was its environmental impact.' To minimise this, the new works will be screened as much as possible. The buildings have been designed to blend in with the landscape and will have roofs with green sedum growing on them.

Solar panels will supply heat to the administration block and a wood pellet boiler will heat the chemical store rooms.

The main treatment building takes sustainability one step further and will be built into the steeply sloping site.

'Building the plant into the side of the hill suits the hydraulic prole of the works, ' says Cole.

But the sustainability efforts paid off whenTaunton Deane Borough Council granted the project planning permission - with no objections - in May 2006.

But the low prole of the buildings did leave the construction team with some pretty hefty excavations when work started on site last August.

'We have a very deep backwash tank and so we had to excavate up to 10m.

One of the biggest challenges was the ground conditions. It was very variable with rock and ll, we think dumped there when the two service reservoirs on the site were constructed.

'As a result we have a quite interesting combination of CFA (continuous ight auger) piles under the granular activated carbon treatment building, vibroreplacement piles elsewhere and the 52m by 30m dissolved air otation building sitting on solid rock.' In total, 50,000m 3 of material was excavated, and in strict keeping with the project's environmental credentials, none was taken off site.

'Wessex purchased the eld above the site to store material and it will be landscaped to suit the natural contours of the land, ' explains Cole.

This in itself posed a challenge, as it opened up the possibility of storm water running off the levelled eld and straight into the deep excavations, Cole explains.

'We had to build two or three 30m 3 attenuation ponds to prevent this, ' says Cole.

The extra site space meant that heavy equipment could be stored on site, minimising the impact of construction trafc on the area's narrow lanes.

Construction of the new works is expected to be completed by 2009, after which the existing works will be demolished.

Who's who

Client: Wessex Water Services Principal contractor: Wessex Engineering & Construction Services Designer: FaberMaunsell Architect: Race Cottam Process contractor: Enpure Site safety AFR: Just one reportable accident to date.

Safety innovations: A dedicated radio band has now been set up for the crane operators - involving one tower crane and two crawler cranes - and has eliminated noise interference.

Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.