Discontinuance of Lower Neuadd Reservoir

Abstract

Lower Neuadd Reservoir was created by an embankment dam constructed in 1884 in what has since become the Brecon Beacons National Park. The dam and spillway have exhibited a long history of concerns surrounding their integrity. The deteriorating spillway channel, faulty scour valve, and the leakage through the core with associated settlement of the embankment dam reached a point where remediation was not reasonably practical. The chosen solution was discontinuance by excavating a notch through the embankment dam. Obtaining permission to alter listed structures within a national park required detailed environmental assessments and negotiation with the authorities. Construction was complicated by a mountainous catchment that created significant flows at low return periods that could fill the empty reservoir basin in hours and overtop the works.