Hydro base emerging from the river bed; screw on order
Great news of the last couple of weeks is that we have stopped digging and started building! The photographs below show the base for the microhydro growing out of the riverbed and we can already see the distinctive curved end of the Powerhouse beautifully cast in concrete.
This means that we are moving swiftly towards the end of the hydro civils with the changeover to the Environment Agency Weir B works taking place seamlessly in the next week or two. Doing Osney Lock Hydro’s work followed by Environment Agency maintenance and repair to Weirs B and A minimises disruption and means that all the work to the Lock and surrounding weirs is done in one go.
We will be able to move on to the most exciting part of the project, to install the generator, early in the New Year. The Environment Agency will follow on from hydro/Weir B civils to do repairs and replacements to the hand radials at Weir A between mid-October and Christmas.
This week we have also placed the order for the Archimedes screw that will generate the power at Osney Lock Hydro. It takes a minimum of four months’ lead-in time for the order to be built and delivered from Holland.
A very good late development is that we have decided to have a variable-speed screw built. This has two very important advantages for Osney Lock Hydro: firstly, it means that the screw will be able to turn more slowly when the river levels are low and therefore operate more efficiently and even more quietly than we were expecting; secondly, it means that the energy in the head of water can be converted to power more efficiently, thereby increasing generation by 15-20%.
Crane in the sunset . Photo credit – David Jeffrey
With the cofferdam in place, water has now been drained from the site of Weir B, so work on the riverbed can commence. The draining of the site also provides a unique opportunity to learn more about its history. A key point of interest is the century old winding gear for the weir.
Oxford Archeology have been commissioned to document the findings, and we are investigating how we might combine the old winding gear into our new design as a way of showcasing and preserving this fascinating piece of waterways history.
In the meantime, we are hearing reports that our crane is proving of interest to residents of all ages – from young toddlers, to the young at heart. Thank you to David Jeffrey for sharing his photo of the crane at dusk.
Construction of the cofferdam started on Monday 8th July. In consultation with the Environment Agency, our contractors have slightly modified the design of the cofferdam. As a result the contractor has implemented a special piling head which as enabled them to use a relatively quiet piling technique using a ‘silent hammer’ or vibro-hammer. We have completed the cofferdam using this technique, however for the rest of the piling we may still need to switch to impact piling depending on ground conditions encountered.
We are dismayed to be once again announcing a further week’s delay to the start of pile driving on the site.
The delay continues to be due to the finalising of the details relating to the leasing of the site. We had a very constructive meeting with the Environment Agency’s legal team today, and expect preparatory works to commence next week, with pile driving itself now due to start on Monday 8th July.
One of the first tasks for the contractors will be to put in a cofferdam, to enable the civil engineering works to take place. It is anticipated that the pile-driving will take around two weeks (10 working days) at the time of writing is now expected to start the week commencing 1st July.
The coffer dam is needed for both the hydro’s civil engineering work and the Environment Agency’s work on Weir B. The weir at the site of the hydro and this maintenance work has been planned for some time.
As part of the preparation of the site, the Himalayan Cedar at Osney Lock was felled today along with a small crab apple tree and some shrubs. This followed a visit by our ecologist to check the site for nesting birds. There were no nests in the felled tree, but the sycamore and conifer trees will be left for a further 14 days because they do contain nests.
We have been disappointed by recent inaccurate stories in the local press regarding the impact of hydro schemes on fish, for example, a piece in last week’s Oxford Times ‘Anglers warn over Thames hydro-plant threat to fish.’ We have felt particularly dismayed given the care we have taken to fully assess the ecological impact of our scheme and in our choice of hydro technology, and of course this information was included in our application for planning permission.
HMRC have informed us that on the basis of the information we provided to them they would be able to authorise OLH to issue compliance certificates for SEIS and EIS once we complete the necessary forms.