The Costelloe Regional Water Supply Scheme was procured in two contracts, a DBO contract for the lake impoundment, abstraction works and treatment (Contract 3), and an Employer Design contract for pipelines and reservoirs (Contract 2). Contract 2 commenced in June 2013 and included the construction of two clearwater service reservoirs (500m³ and 1,700m³) and approximately 7.5km of water main. The construction stage was completed in May 2014. Contract 3 includes a Dam & Fish Pass at Glenicmurrin Lough, a pumped abstraction (3,600m³/d) and 4km of raw water rising main, and a Water Treatment Plant and pumping station. Contract 3 has been progressed as far as the tender stage for construction. TOBIN role included the design of the regulating weir and fish pass to impound raw water on Glenicmurrin Lough and facilitate fish migration. Modeling of Pre- and Post- Works reservoir behaviours under different combinations of flood flows, low flows, and compensation water allowances were carried out to ensure that the proposed scheme does not adversely impact water quality, aquatic and terrestrial ecology, and in particular salmonids and other fish species. This included establishing a satisfactory flow regime in the outlet channel from Glenicmurrin Lough to ensure that it provided sufficient flows (particularly spate flows) to accommodate the migration of fish species.
The project has involved significant consultation with a number of stakeholders including the Fisheries Manager, NPWS, IFI, GCC, DCENR, to ensure that the proposed dam and fish pass accommodates the requirements of all parties. A feasibility study was completed of several alternative fish pass options including a rock ramp style fish pass. The options were presented to a number of representatives from Inland Fisheries Ireland and the Department of Communications Environment and Natural Resources (DCENR) based on which a preferred solution was identified. TOBIN prepared the application to the DCENR, based on which approval was obtained for the impoundment and fish pass as required under Section 115, Paragraph 2, of the Fisheries (Consolidation) Act, 1959. TOBIN prepared a detailed design for the approved option which was incorporated as part of the Works Requirements for Contract 3. TOBIN developed a detailed operating policy for the sluice gates and fish pass to optimise fish migration through the fish pass, and this was included as part of the Contract Specification. This operating policy was subject to a detailed independent specialist review.