Impact on Fish
The environmental Impact Survey used data supplied by the Environmental Agency fisheries surveys and other locally available data. Archimedes screw turbines are considered the most fish‐friendly of hydropower installations. The helical nature of the screw blade within an Archimedes screw turbine means that there is just one main point of collision potential, in the form of the leading edge of the screw (tip). Upon entering the screw, fish effectively remain within the same body of water moving downwards within the chambers of each individual flight. Mechanical fish injury potential is therefore limited.
Although there is a fish pass on the existing Goring Weir complex it does not comply with modern standards. As part of the hydro scheme a new 2.1m wide Larinier fish pass is being installed by the Hydro project. This new fish pass will be a great improvement on the existing arrangement.
Impact on other Species
A desk top study was undertaken with reference to the National Biodiversity Network (NBN) Gateway and consultation with Thames Valley Environmental Records Centre (TVERC) and the local library to ascertain if any notable and legally protected species were present. A Phase 1 Habitat Survey was undertaken in June 2008 to establish baseline data for the existing environment. The survey area lies within the River Thames and is limited to 100m upstream of Goring Weir to 250m downstream. The basic techniques for the fieldwork adopted the Phase 1 Habitat Survey as devised by Natural England. In addition, searches were made for any protected species either seen directly or inferred from field signs such as burrows, droppings or tracks. Suitability for species such as bats or water voles was also assessed.
The conclusions included that as virtually all the construction works will be undertaken from working barges it is not anticipated that there will be any significant impacts on the terrestrial habitats.
River Corridor and Macrophytes (macroscopic aquatic plants)
Goring Weir was surveyed in June 2008 using standard River Corridor Survey methodology as detailed in the River Corridor Survey Handbook (National Rivers Authority 1992). Normally in these surveys the river is divided into 500 m sections but as the entire survey area in this instance was only 350 m the whole area was considered as one site.
During a thorough walkover of the site, both banks were surveyed and dominant vegetation in each of the vegetation zones was recorded and mapped. A channel cross‐section was drawn to indicate features such as depth of water, bank height and adjacent bank use.
The conclusions indicate that the main area to be affected by the construction of the proposed installation will be around the weir and there are no significant macrophytes present in this area; and there will be no significant impacts to macrophytes during operation of the proposed installation.
Comprehensive sampling for macroinvertibrates was conducted. The environmental report concluded that during the construction period the weir will still be operating as normal with the exception of the area between the fish pass and the lock, which will be dewatered. Only a small area of riverbed immediately surrounding the weir where the turbines will be installed will be temporarily uninhabitable for water macroinvertebrate species during construction work. This temporary loss of habitat will result in only a negligible temporary impact to the populations distributed along this stretch of river. It is anticipated that once the riverbed becomes available following the construction phase the same populations will reinhabit the area.
A total of three screws of 3500mm diameter will be required to handle the maximum design flow of approximaytely 20m3/s, and these will be arranged side by side directly on the section of weir closest to the lock keeper’s house. Water will flow into the screws across the site of the existing weir crest, and discharge close to the bottom of the existing weir. It is hoped that thehe screws will be fully visible, but ths may be obscured by acoustic covers. The control room structure will be by the lock-keepers house and the top of it will be lower than the existing walkway and will be finished to match the existing structures.
A baseline noise survey has been completed by Spaans Babcock. We expect planning conditions on noise both during operation and construction phases. However, we have evidence from similar ad larger completed installations that the proposed installation will be completely acceptable
A baseline noise survey has been completed by Spaans Babcock. We expect planning conditions on noise both during operation and construction phases. However, we have evidence that the proposed installation will be completely acceptable.
A key finding from the 2010 flood risk Assessment was that “The results show no significant increase in flood levels. This, despite the conservative nature of the modelling that simulates a complete blockage of a 13m section of the weir (in reality some flow is likely to be able to flow between, through or over the turbines). There is therefore no increase in flood extent or flood risk to third parties as a result of the development proposals” (Peter Brett Associates, 2010).