Environmental

Teddington and Ham Hydro was formed out of an award winning environment focused community group. As such we are extremely committed to ensuring that not only does our project not cause any damage to the environment but also wherever possible helps to safeguard it for the future.

Because the output of the scheme is under 500kW, it does not require a full Environmental Impact Assessment. Nevertheless, we have undertaken surveys of the weir pool and its surroundings (e.g. fish, flora and fauna): the summary of those surveys is here: Environmental Surveys.

Fish migration

Archimedean screw hydro power turbines are regarded by the Environment Agency as the approved hydro power technology for low-head run-of-river schemes. There are many other such schemes in operation in the UK and abroad and tests carried out both here and in the Netherlands have demonstrated conclusively that the turbines have no detrimental impact on fish (“… over 100 screw turbine systems are currently operational on the continent, with no reported fisheries issues or problems”, from “Archimedean Screw risk assessment: strike and delay probabilities”, Kibel and Coe, 2011). The design of the scheme includes screening which will only allow fish of a certain length to pass through the turbines – in fact, fish which do pass through the turbines will suffer no ill effects. If you wish to see a video of fish passing through an Archimedean screw turbine, please visit http://www.fishtek.co.uk/hydropowerresearch.html.
From the start of our project we have insisted that our design should attempt to enhance fish passage at the weir: our design includes a 3 metre-wide Larinier fish pass with varying gradients to attract a variety of species. This is a clear upgrade of the current situation: there are currently two 1 metre-wide salmon passes in place.

Eel passage

Despite the fact that eel populations are in decline throughout Europe, currently there is no provision for eel passage at the weir. As part of our design, we will install an eel pass to remedy this situation.

Bats

A bat survey was conducted in 2012 which indicated “no predicted impacts on bats during the construction phase …or the operational phase of the turbines”.

Flood risk

A Flood Risk Assessment was carried out in 2011, and updated in 2013, which showed that the scheme’s impact on the risk of flooding was “negligible”. In concrete terms (no pun intended), this means that in the “1 in 100 year plus climate change flood event” (i.e. the worst-case scenario) the river level would be increased by under 10mm in the upstream reach of the river. The results of the flood risk modelling show that, with the Thames Barrier operational, river level increases directly upstream by 9mm and the upstream reach as a whole is 2mm lower than the baseline.