Rehabilitation of the Upper and Lower Bohernabreena Spillways

摘要

The Bohernabreena Reservoirs are located south west of Dublin on the Dodder River. The reservoirs are in cascade; the upper reservoir used for supply of raw water to the Ballyboden treatment works; and the lower reservoir for flood relief. Both dams are puddle clay core embankments of the 19th century. The dams are owned and operated by Dublin Corporation. The reservoirs are situated upstream of Dublin and therefore require an 'A' categorisation with a PMF discharge requirement. Due to constrictions formed by the crest road bridges across the chutes, the actual capacities are only of the order of 100 year return period. The spillways are to be replaced with new reinforced concrete structures while the structures remain operational. Careful planning of temporary works and understanding of the hydrological risks are necessary to ensure that the embankments are protected.