Built in 1969 Siblyback Dam is a concrete arched structure 21.3 metres in height and 229 metres in length. The reservoir capacity is 704 million gallons with a maximum depth of 18 metres over an area of 60 hectares. Following an inspection under the 1975 Reservoirs Act, pdp Green were commissioned to undertake a structural analysis of the stability of the dam under a combination of onerous loading criteria including flood conditions and seismic loading. In addition pdp Green undertook a comprehensive CCTV survey of the pressure relief well system. As a result of the investigation, some remediation work was required, including drilling and probing work of the pressure well system where it was partially blocked.