The works by contractor Balfour Beatty Civil Engineering (BBCEL) will see the development of 28km of new dual carriageway on the A46 in Nottinghamshire, while the SUDS scheme will be used to achieve pre-development surface water run-off.

This is in accordance with Environment Agency guidelines which require flow restrictions to be held at the predevelopment rate for greenfield run-off, in order to ease water volumes into local watercourses and control water quality.

Work started on the upgrade scheme started in 2009, and is set to be completed by summer 2012.

According to the Highways Agency, the upgrade will improve traffic flow and safety, while by-passing several villages.

However, it was faced with the challenge of doubling the surface area of the metalled Newark to Widmerpool trunk road, which would have created unacceptably high surface water runoff.

As a result, Balfour Beatty and consultant engineers, URS Scott Wilson designed a series of 12 balancing ponds with the outfall from each controlled by a hydro-brake flow control device.

The balancing ponds are designed with a permanently wet sump area and vegetated dry sections to ensure optimum entrapment of debris and silt at most stages of inflow.

BBCEL site engineer Steve Sloan, said: “A series of 12 balancing ponds of differing sizes were constructed, accepting flow from between 800 metres to two km of highway. They discharge into many different watercourses along the route, and the Hydro-Brake is widely recognised as the best flow control device for these projects.”

Carys Matthews

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