November 2011 update
Nov 18th, 2011 by lizziethatcher lichfielddc.gov.uk/chasewaterdam…
Most of the main works to the north of the canal are now complete, although we still have to install drainage pipes through the sheet piles and carry out further landscaping works on the north eastern area next to pool cottages.
The repair works to the canal basin are also nearing completion, although the reconstruction of a concrete cover slab over the drawdown outlet is still to be done. This should be cast within the next few days.
Water levels in the reservoir are rising, albeit quite slowly at the moment. The water is now almost level with the top of the sheet piled dam around the inlet to the drawdown tunnel.
The two valves in the main valve house which are used to release water from the reservoir into the canal have been repaired – one of them had jammed shut and the spindle which operates it sheared away – if you watch our video Dam Cam Goes in Deep – you can see this in detail.
The maintenance regime that we have introduced for the valves will mean that we will have to open them briefly from time to time to ensure that they remain operational, but there is a secondary valve further downstream in the drawdown culvert which will make sure that we do not lose too much water from the reservoir during these tests.
Most of the construction activity is now concentrated on the Nine Foot Pool area. We recently completed the overflow bridge wing walls and started backfilling this and the sheet piled cut off wall.
Work is progressing well on the construction of the bases to the retaining walls which will run either side of the spillway area downstream of the weir.
Because of Galliford Try’s planned construction sequence and the need to have access through the whole of the Nine Foot Pool and spillway area, it is likely that the weir itself will be the last structure to be built in the New Year.
The SCC team
Nov 18th, 2011 by lizziethatcher
In response to various queries that we receive from time to time, we have included below a few FAQs relating to the reservoir and dam works:
- When will we be able to walk across the dam?
If it is safe to do so, we are hoping to temporarily open the footpath along the crest of the dam to walkers over the Christmas period when the site will be shut down. This, however, depends on the stage that the works at the Nine Foot Pool and in particular, the overflow bridge, have reached at that time. Unfortunately, we will then have to reclose the access over the bridge in the New Year to enable us to complete the outstanding works and the path across the dam will then remain closed until the project is completed in Spring 2012.
- When will the dam work be finished and the site cleared?
Subject to weather conditions over the winter which could delay progress, we are currently planning to complete the works and clear the site by late March/early April 2012.
- Where does the water come from that feeds the reservoir other than rain water?
The reservoir has what is known as a “catchment area”, an area of land over which rain water, ground water and some drainage run-off collects into various streams and watercourses which ultimately flow into the reservoir.
The catchment area for Chasewater Reservoir is about 9 square kilometres and lies mainly to the north of the reservoir. The main dam was built across the valley of the eastern Crane Brook which rises in high ground in Burntwood and flows into the reservoir along Blackman’s Gutter and into the inlet where the sailing club is now sited.
The secondary, western dam retains streams such as the Big Crane Brook from Biddulph’s Pool and other ponds to the north which before disturbance by mining subsidence and open cast mining flowed into the River Penk to the west.
- When will the sailing and powerboat clubs be back open?
This is entirely dependant on the water level in the reservoir and, therefore, the rate at which it refills. The reservoir level is currently around 144 metres above ordnance datum (AOD). Based on historical records and current rates of rainfall, it has been estimated that it may be the summer of 2013 before the reservoir starts to reach normal operating levels of between 150 and 152 m AOD. However, the sailing and power boat clubs can operate in lower water levels than this and so may be able to open a little earlier.
- Will Pool Road be reopened, when the dam is finished? If not, why?
It is our intention to seek to close Pool Road to all traffic other than for access to the properties on Pool Road after completion of the works, however, this will be subject to a statutory consultation exercise.
- Will there be a DVD released of the works involving the dam and of the hidden chamber?
We don’t anticipate releasing a DVD as such but video footage of the drawdown culvert and hidden chamber was included in an earlier blog update.
- Will they remove all the debris and plants before it refills?
Some willow growth will be removed but other plant growth will not. This will die out naturally as the reservoir fills.
Debris will be removed where it might form a hazard to boat traffic or is regarded as waste.
- Will fish be put back into the reservoir?
There is no requirement or intention to put any fish back. We estimate that a small proportion of the total fish stock was removed. The majority of fish removed were predatory which may actually benefit the water body as smaller prey species may now be more prolific. In addition there will be a large flush of nutrients through re-fill which will ultimately facilitate the quick expansion of the fish populations.
- Can you explain, ‘What is the plug that has been put back in?’
A critical part of the works was to ensure that the brickwork tunnel (the “drawdown culvert”) which runs under the eastern dam from the bed of reservoir and which is the means by which water is released into the canal system was in good condition and fully functional.
Until this work was complete, water levels in the reservoir had to be kept down. Having completed these works, there is now no need to continue to release water from the reservoir and it can now be allowed to refill naturally.
- Is there really a plug?
- There is no actual plug but the valves that control the flow of water out of the reservoir are now shut.