Project Brief

The new 7.7km Great Barford Bypass is being constructed to alleviate heavy traffic on the A421 on its way to Bedford and on to join the M1. In order to attenuate stormwater runoff from the highway, 6 balancing ponds had to be constructed.

Marshalls Civils and Drainage Solution

After investigating several options Marshalls Civils and Drainage presented a joint venture between themselves and Hydro International, offering Hydro-Brake® Chambers that would help reduced installation costs and land requirements compared to other conventional techniques.

The 6 balancing ponds range in size from 500 to 1500m³ and are designed with normally wet sump area and a normally dry, but vegetated area to ensure excellent entrapment of debris and silt at most stages of flow. The outflow of each pond is fitted with a Hydro-Brake® Chamber. The principle benefit of the Hydro-Brake® Chamber is that no benching or coring is required during the installation.The concrete chamber is prefitted with the Hydro-Brake® Flow Control complete with preformed benching and headwall . The one-piece chamber reduces the need for concrete surround and the semi-circular benching allows easy access to the sump area for sediment removal.

Client Comments

“Because of a wide range of flow conditions, the Hydro-Brake® Flow Control device maximizes the amount of discharge in line with the Environmental Agency’s limit of 4 litres/second/hectare of contributing area; we are able to reduce the amount of storage required for the balancing ponds. This helps reduce the land take for the tanks as well as the costs of construction.”

Albert Kontoh, Consulting Engineer, Capita Symonds Group

“From a procurement point of view, ordering pre-cast chambers with the Hydro-Brake® already fitted wins on quality and was a good reason for going through Marshalls Civils and Drainage .”

Mike Brookes, Project Manager, Edmund Nuttall