Protection of the water environment using balancing facilities.

A monitoring programme of water quality was carried out during wet and dry weather conditions in two balancing ponds adjacent to the A34 Newbury By-pass. The ponds were constructed to treat and store stormwater runoff. Pond B was a vegetated pond planted with Phragmites australis and Pond F/G was a constructed wetland with a sub-surface flow system and P. australis at the inlet and, initially, Typha latifolia at the outlet although this was later replaced by Phragmites. There was little difference between the pollutant removal performances of both ponds although Pond F/G was sometimes more efficient in removing nickel and nitrate and zinc during the summer. Recommendations are made for the design, construction, operation and maintenance and future monitoring of wetlands for highway runoff treatment.

R&D Technical Report P2-215/TR.