The Abberton Scheme
Causeway across the reservoir
Essex is the driest county in the UK and, in the early 1990s, it became clear that more water was needed to meet future demand. Essex & Suffolk Water (ESW) was already doing all it could to reduce demand for water, so it decided to expand the existing Abberton Reservoir, near Colchester.
ESW's Abberton scheme was the first major water resource development in the UK for 30 years. It raised the reservoir's water level from 26bn to 41bn litres, and will supply water to 1.5 million people in Essex for many years to come.
Abberton Reservoir is also designated as a Site of Special Scientific Interest (SSSI), Special Protection Area (SPA), and a Ramsar Site (wetland of international importance) for wildfowl. ESW's team needed to protect and, if possible, improve this important habitat. The scheme included creating 6ha of wetland mitigation habitat, and removal of the concrete edge and shoreline re-profiling. This provided a further 200ha of shallow water habitat, which is crucial for feeding wildfowl.
Meeting the challenge
Abberton Reservoir pumping station
Getting planning approval on time was critical. However, this was complicated by the geographical size of the project, which meant planning permission was needed from four separate authorities.
Planning applications included a substantial Environmental Statement, containing a comprehensive impact assessment, to reflect the high ecological value of the landscapes involved.
Abberton Reservoir needed to be kept open throughout construction. The complicated geotechnical history of the main dam called for rigorous consideration of design. Finite element analysis was used to model the dam and the design was checked by an external panel of independent dam engineers.
The sustainability of the scheme was of paramount importance. As well as protecting habitat, it was important that the wider environment was preserved.
The dams were designed to use clay, sands and gravels sourced solely from within the reservoir site - over 800,000m3 in total. The original 12km concrete perimeter was excavated and crushed on-site to generate 35,000m3 of recycled material for constructing the new 17km perimeter track. These elements helped to reduce off-site waste and the amount of material that had to be imported. This resulted in 35,800 fewer journeys on public roads, 849tons of CO2 emissions being avoided, and much less disruption to local residents.
The large steel frame building, which housed the temporary off-take pumping station, was dismantled and re-used at another ESW site.
Involving the community
Key to the project's success was keeping communities informed and part of the decision-making process. This was done through public meetings, site tours, drop-in sessions, website updates and newsletters. More than 100 public meetings were held before the planning submission, involving nearly 100 interest groups and local communities. Drop-in sessions were attended by over 700 local residents, who were overwhelmingly positive.
A successful project
The £150m scheme was delivered on time and within budget. It was funded through ESW's capital investment programme and long-term loans. Upgrade of the Ely and Ouse to Essex Transfer Scheme (EOETS) took place between 2010 and 2012. Construction at the reservoir started in January 2010 and was completed in December 2013. The reservoir exceeded the original top water level in January 2014.
The scheme has won many awards and was cited as an example of best practice in the 2012 Government review of the Habitats Directive.