Water & Wastewater Treatment

B1026 road, with its western section retained as a marshland habitat for birds will formally www.wwtonline.co.uk | WWT | MAY 2015 | 15 reservoir, embark on an aquifer storage and recovery (ASR) scheme, or enlarge an existing reservoir. The first option was seen as economically unrealistic without partnering with another water company, while aquifers in the region were judged unsuitable for ASR; so the third option was chosen, with Abberton preferred over E&SW's other reservoir, Hanningfield. "Once we'd finally decided on Abberton, the next thing we needed to decide was how much we'd raise the water level by," says Jenkins. "It was clear that if we wanted to raise it by more than 4 metres, the amount of work required would have put the price up exponentially – we would • Perspectives Heidi Mottram, Chief Executive, Northumbrian Water Group: "I think everybody knows how precious water is and how Essex is one of the driest parts of our country. We're delighted to have delivered the Abberton Reservoir expansion project on-time and on-budget and as a result secured water for our customers in Essex for many, many years to come." John Devall, Water Director, Essex & Suffolk Water: "It is fantastic news for our customers that Abberton Reservoir is now full and it represents 23 years of detailed planning and hard work to get to this point. We are incredibly proud of how this essential project has been delivered in a sensitive way that also vastly enhances this internationally important wetland and provides lasting community benefits." B1026 road, with its western section retained as a marshland habitat for birds • Innovations ● Computer modelling used to calculate optimal reservoir level ● Areas of shallow water maximised to retain wading bird habitat ● Reservoir split into new impounding and pump storage sections literally have had to build a wall around the reservoir rather than use its natural contours. So we concen- trated on fractions of a metre between 3m and 4m, and it turned out that 3.2m was the optimum in terms of cost versus yield." Environment-conscious design However, the reservoir's SPA status meant that the company had to satisfy Natural England, the governmental advisory body, that the new reser- voir would have an equal or greater amount of water that was 0-1m in depth – a crucial habitat for wad- ing birds. The design incorporated pools and ponds around the reservoir edge to fulfil this requirement, while concrete edging was removed to give a more natural look. A significant sec- tion of water, west of the B1026 road which divides the reservoir, was also set aside for further environmental improvements and the creation of additional marshland with the aim of attracting birds to roost and feed in this section. By blocking off a culvert under the road, the project has ef- fectively split the reservoir into two, with this Western section retaining its initial water level. Extensive environmental studies and consultation were also required for the expansion of the transfer scheme to get off the ground. In order to win the license to abstract more water at Denver on the River Ouse, the project team had to carry out envi- ronmental impact assessments on the Great Ouse and in the Wash, a process which took around ten years. "The Abberton scheme was basi- cally in three parts," says Jenkins. "The first part was getting the varia- tion in the abstraction license for Den- ver, which would allow us to take the extra water. The second part was the improvement in the transfer scheme - the rivers, pipework and pumping stations to get the water down here - and then the third part was enlarging Abberton reservoir itself." The transfer scheme itself was a multi-stage project. A pre-existing channel carries the abstracted water as far as Kennet, near Newmarket, where a pumping station needed to be increased in capacity to cope with the additional water. From there, the water is pumped to the River Stour. A new pipeline was required parallel to the river, because the upper reaches of the river were incapable of carrying the extra flow; a new abstraction point and pumping station was then created at Wormingford lower down will formally

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