Scottish dam withstands further flood danger

The Maich dam is a small 24000 m3 capacity earthfill embankment located in the valley of the Maich Water on the border of Renfrewshire and North Ayrshire north-east of Kilbirnie.

The dam was very badly damaged by overtopping during a flood on Friday 1 August and there were concerns that the dam would fail. However pumps were set up to lower the water level, and take the load of the dam and the water was diverted round the reservoir via the repaired bypass channel. By Tuesday the risk of failure had reduced considerably and arrangements for demolition of the embankment were commenced

However on Wednesday night a further major rainfall event washed out the temporary repair to the by-pass channel and refilled the reservoir. Roads were again closed and nearby homes evacuated.

The by-pass channel was reinstated on Thursday using large diameter plastic pipes. Pumping re-commenced and lowered the water level by about 3.5 m by Friday morning.

More heavy rain was predicted for Saturday afternoon. Contractors worked long hours on Friday and Saturday to excavate the dam and install a rock armoured toe using re-used pitching stone.

"This provided a low overtoppable bank retaining a small pond of water and silt about 2m maximum depth," said Faber Maunsell associate director, Robert Mann.

"The platform and armoured toe were completed in increasingly wet conditions at noon on Saturday and the public emergency was declared over."

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