Fish Guidance Systems (FGS) were asked to provide screening for a range of course fish and also salmon smolt in the spring, following salmon being re-introduced into the River Thames. However, with the ever-increasing population of London, combined with the increasing potential for droughts as a result of climatic change, concern was expressed that water shortages may occur. The need to find a solution was heightened with the risk that there may be water shortages during the London Olympics in 2012 if a drought were to occur. FGS has previously installed acoustic fish deflection systems on all of Thames Water’s drinking water intakes, Thames Water reviewed the option of abstracting more water from the existing intakes, but the River Thames was identified as already being under stress, and so a new water intake was required. The decision was made to install the new intake at Beckton, on the northern shore of the River Thames, downstream of the freshwater boundary at Teddington Lock. This would require the building of the first desalination facility in the UK, which would be capable of treating the brackish water and producing 150,000 m3 of fresh water per day. In order to minimise the salinity load on the plant it was designed to abstract all of the required water during the three hours immediately before low water, when the salinity would be at its lowest. A new intake was constructed alongside an existing jetty approximately 150m from the shore, but concern was raised about the impact of the intake on the fish population in the river and so wedge wire screens were proposed. However, it was concluded that the wedge wire screens would not protect the vulnerable species of fish, such as sand smelt (Atherina presbyter), which may be impinged on the screens and so an acoustic system was specified to help protect this delicate fish species.
FGS was therefore requested to specify and supply a suitable fish deflection system. Acoustic modelling was carried out to determine the optimum acoustic system for the intake, and a number of alternative systems were tested, but all of the designs were based upon skewing the sound field to the upstream side of the intake, since the system was only required to operate on a falling tide. Whilst locating the Sound Projectors on the surrounding piles would have created the optimum system, the lack of access resulted in the Sound Projectors being located immediately adjacent to the screens, where they could be deployed from the new walkway over the intake. Since the acoustic deflection system was only intended to protect the sand smelt the minimum sized system was installed, but with spare Sound Projectors being maintained on site to enable a unit to be quickly swapped out in the event that a fault occurs. A Diagnostics Unit was installed to monitor the system and provide the alarm in the event that a fault occurred,
The system was installed in 2009 by the main contractor, and FGS subsequently attended the site to commission the system and provide Operation and Maintenance training for the Thames Water Engineers responsible for the system.
