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25 Sep 17

Seeing the trees for the wood

One of our motivations behind constructing a hydro in Greenburn is that it will provide an additional source of income to invest in our conservation work in Little Langdale. One particular ambition we have is to return the small larch plantation that spans Greenburn Beck back to native broadleaf woodland and develop a woodland corridor alongside the beck up to the fell wall. Our rangers have been out surveying the existing trees and the investigations have revealed that whilst the larch trees dominate the plantation visually, there is actually good broadleaf tree cover around them - oak, beech, birch and rowan. Therefore, by selectively thinning the Larch we will open up spaces in the canopy for regeneration of native woodland from the seedbank in the soil below. Whilst some of the larch will be felled and extracted, we plan to leave others on site as valuable deadwood habitat for invertebrates.

Woodland ranger carrying out tree survey along the Greenburn beck

08 Sep 17

Statistical overload

For those of you who are looking for facts and figures, here are some numbers to help put the scale of the scheme into context: The intake itself, which removes water from the beck, is a 1.5m wide screen covered in 1mm holes, which at peak water flow can remove up to 94 litres/sec. This is the ‘consented flow’ which is a calculated by the Environment Agency following a years’ worth of beck monitoring. It ensures that more than enough water is left so that the hydro does not negatively impact on downstream habitats. The chamber acts as a header tank, which means that only when sufficient water pressure is maintained at a consistent level will the turbine start. There is a sensor within the chamber which measures the head and relays these levels via a signal cable to the turbine. The chamber is approximately 30m3 and can therefore hold 30,000 litres of water. As a result we will be casting up to 10m3 of concrete to ensure the chamber is both water tight and able to with stand the pressures it will be subjected to. All in, quite a feat of engineering.

Metal and wooden form in place in the ground ready to take the concrete for the intake structure.

01 Sep 17

On to the intake

August has shown all the hallmarks of a typical British summer; wet and wetter still. This has made conditions on Greenburn challenging. Undeterred, progress continues to be made at the intake, as evidenced by the not-so-insignificant hole we now have there. Excavators have pecked out the bedrock to create the area where the main chamber will sit next to the intake. Water will flow from the beck into this chamber, via the intake, before it travels down the 1.2km pipe to the powerhouse. Joiners are currently building the timber shuttering for the chamber framework, into which concrete will be poured to form the structure. It sits below the ground surface and so eventually will be completely obscured from view.

Bedrock excavations for the chamber and intake