Articles & Case Studies

RESERVOIR CONSTRUCTION IMPROVES WATER SUPPLIES IN SOUTH EAST

Posted: Wednesday 27th June 2012

Leading civils contractor, J. Murphy & Sons Limited was awarded a five year framework contract by South East Water (SEW) in 2010 to improve water supplies in Surrey and Kent through the design and construction of four new Service Reservoirs.reinforced concrete treated water reservoirs.

Stuart Griffiths, Contracts Manager, provides an overview of the whole scheme, as well as an account of the successful completion of the first reservoir at Hindhead in Surrey.

The scheme is part of South East Water’s £390m investment programme between 2010 and 2015 as part of the AMP5 programme to improve its network of water mains, refurbish existing or develop new water sources, and ensure customers continue to receive high quality potable water for their homes and businesses.

The framework concentrates upon new service reservoirsreservoirs to be located where the existing reservoirs are either reaching the end of their operational life or provide insufficient capacity. The framework provides for, a new 5MlLD service reservoir at Hindhead in Surrey, a 10MlLD facility near Aylesford in Kent, and two additional storage schemes in SEW’s western region. . All the service reservoirs are The existing reservoirs are either reaching the end of their operational life or provide insufficient capacity and multiple cell.s are being provided at each location

As principal contractor, Murphy is responsible for the design and , enabling and construction, plus associated site investigation, earthworks, civils and pipework, process treatment support and landscaping.

Hindhead

The first reservoir to be for constructedion was the Hindhead Service Reservoir (SR) in Surrey, which has been built at an existing site off the A3. This and will benefit more than 12,500 customers in the Hindhead, Grayshott, Bramshott areas in the supply of household water. Following steady population growth and a need to maintain water quality, South East Water initiated the scheme as part of its AMP5 programme.

2/…Hindhead is a town 10 miles south west of Guildford in Surrey and boasts the site of the Devil’s Punchbowl, an Area of Outstanding Natural Beauty with a dramatic landscape covered in mixed woodland and heath.

Owned by the National Trust it is environmentally highly prized with much flora and fauna, including protected species such as the Dartford Warbler, as well as reptile populations such as adders and slow worms.

Hindhead SR is a 5MlLD (5,000m3) capacity enclosed twin cell reinforced concrete structuree, and is rectangular in plan with an integral concrete roof. It is partially sunk below ground and the sides of the reservoir will generally be covered by reinforced earth embankments which will be grassed and the roof covered with gravel.

The project involvedcontract has comprised the design of the reservoir and associated pipework connections to the water network, local water treatment arrangements, dosing point, booster pumping chamber on site drainage and the refitting of the existing operations building.

The reservoir is an enclosed reinforced concrete structure partially sunk below ground and the sides of the reservoir will generally be covered by reinforced earth embankments which will be grassed and the roof covered with gravel.

The overall footprint of the reservoir including the embankments is approximately 50m by 20m with a height above the existing ground level ranging from 5m to 6m, and is located just south of the existing reservoir.

Environment and Planning

Following detailed reptile surveys undertaken during 2007 the site was found to be exceptional for reptiles. A reptile exclusion fence was erected and a programme of trapping and removal on site undertaken throughout summer/autumn 2010. A hibernaculum was constructed within the Devil’s Punchbowl, and all of the reptiles relocated to this new habitat. Grass was then strimmed short prior to construction to prevent re-establishment of a suitable reptile habitat. It is anticipated that the reptiles will naturally re-colonise the site on completion of the works and removal of the exclusion fence.

Other environmental aspects included surveys for bats and nesting birds at the site, particularly in the existing Operations building, and prior to felling of trees. Archaeological mitigation consisted of investigation and recording of the site by a qualified archaeologist as topsoil and subsoil was stripped.

The close proximity of the Devil’s Punchbowl required the visual impact of any new construction to be minimised wherever possible. As a result, as with the old reservoir, the new reservoir was therefore constructed part-buried and is surrounded entirely by grass embankments. Local residents were kept closely informed throughout the works.

Project management

Operationally Tthe projectscheme was a very challenging one. Built in the early 20th Century, the the operation side due to the age of the existing reservoir on the site meant that , in that, due to the age of the existing reservoir the change over from old to new required a detailed proved to be demanding in understanding of how the old reservoir operated in the supply to residents in the area, to maintain that supply once the new reservoir was commissioned.

Murphy decided to use a propriety shuttering system which would allow concrete wall pours to be constructed on a daily cycle which kept the programme on track.3/…Given the environmental sensitivity ofn this scheme, being located in an area designated SSSI; and the need for timely completion, SEW made the contract a triple SSI and key KPI measures performers were financially linked to delivering zero environmental incidents, as well as rewarding programme and reporting compliance. a monetary incentive only to be paid on monthly performance.

SEW also encouraged Murphy, as the delivery contractor, to identify innovative ways of encouraging and rewarding good Health and Safety performance. This resulted in monthly incentives, including shopping vouchers, for maintaining zero accidents on the contract. These This proved highly effective in engaging staff in the H&S culture.

Murphy decided to use an innovative propriety shuttering system which allowed concrete wall pours to be constructed on a daily cycle, keeping the programme on track.

Delivery

The construction of the reservoir was completed on programme within 10 months despite some seasonally poor weather and challenging pipe-work. The pipe-work connects the new booster chamber with a new MEICA fit out to the existing pump-house to bring on-line the commissioning of the reservoir.

Murphy’s detailed project management-led approach to Hindhead, resulted in the scheme being completed on programme, . This has allowinged the second service reservoir (Aylesford) to commence using the same successful SEW–Murphy integrated approach.team and approach. within both the SEW integrated delivery team, and Murphy.

This in itself has enabled efficiencies to be realisedmobilised, to the benefit of the customers, the stakeholders, and to the overall programme. Lessons learned from the first project are being taken forward and utilised at Aylesford.

No two contracts are ever the same and Aylesford is already proving to have a different set of challenges to Hindhead. The geology at Aylesford is totally different, leading the Murphy designers to change the base construction to suit these ground conditions. Furthermore outputs from the lessons learned workshop for the Hindhead Reservoir are being successfully deployed at Aylesford, which focus predominantly on the involvement of the entire project team at the front end of the project, to the benefit of all parties.




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