Sandford Hydro, Sandford on Thames

Sandford Hydro was our first project working with Fergal Contracting Co Ltd. The project saw the restoration of the Lasher Weir near Sandford to its historic role as a provider of clean energy.  The hydro scheme generates an impressive 1,600 MWh of renewable electricity per year, which is the equivalent demand for around 450 households. Sandford Lock hydroelectric plant uses Archimedes screw to generate electricity from the flow of the river water. The works also included the installation of a fish pass; a system specially designed to allow all the species in the river to safely pass the screw, and the first of its kind in the country.

The housing for the Archimedes screws consists of three main inclined support areas or chambers. Each chamber contains a screw with embedded steelwork frames and cast-in bolts to support the screws. The chambers are almost 5m wide and over 16m in length with walls up to 7m high. Furthermore, we constructed a suspended slab for the generator housing above and behind the screws.

We formed the lower channels for the structure using a bespoke timber shuttering system constructed on-site. The most challenging part was forming the channels for the screws along the line of the slope. We meticulously planned these to ensure the creation of the correct angles, therefore guaranteeing the screws’ ability to securely sit in their chambers while still being able to rotate. After completing the pour on the initial channel, we could reuse the timber formwork and move it to the subsequent channels to produce an exact replica of the initial shape.

We constructed the vertical walls using traditional steel shuttering techniques, with Murform supplying all formwork equipment. Specifically, we formed the 350mm radius bullnose curved central wall elements utilising a recycled steel formwork system. We adapted this system from a prior project to meet the specific requirements of the Sandford Hydro project.

All concrete supporting elements of the screw chambers and surrounding hydro plant structure were cast in situ.  Grade C40 concrete was used to ensure strength, and longevity and provide increased resistance to the environmental factors the structure will face over its lifetime. The hydro structure and the fish pass used a total of 976m³ of concrete and 101 tonnes of steel rebar to complete.

In 2018, the Concrete Society shortlisted this remarkable project for an award!

Photo Credit: Low Carbon Hub