Dear Paul,
 
Thanks for attending the meeting and for your feedback.
See below for answers to some of the questions you raised.
 
Kind regards,
Pete
 
Pete Kibel 
Fishtek Consulting 

On 3 October 2010 18:27, Paul Kenyon <pkenyon@pkenyon.entadsl.com> wrote:

Dear Pete,

Thank you for inviting me to the meeting on Wednesday 29th September to discuss the proposed Archimedes Screw installation at Gara Bridge on the Avon.

I have now had a chance to study your report of the potential impact of the proposed development on the fisheries ecology of the river. It would help to have relevant documents in advance of any future meetings. I have also read the Environment Agency (EA) “Good practice guidelines to the environment agency hydropower handbook

As I explained at the meeting I am a trustee of the Avon Fishing Association AFA which was formed in 1885 to improve the fishing in the River Avon.

I am convinced that Julia will not take any action that could damage riverine ecology. However it is my responsibility to take the long view and consider what might happen if there was a change of ownership at Gara Mill and we had to deal with a less understanding riparian owner.

Fish passage over the weir

The Salmon and Freshwater Fisheries Act (1975) requires the EA to maintain, improve and develop all freshwater fisheries, and to ensure the free passage of migratory salmon and sea trout.

Western Renewable Energy (WRE) stated that “Fish passage over the weir is not considered to be a significant issue, and neither has the pre-application raised this as a significant issue at this location” (WRE, Supporting Documents, page 8).

I do not agree with WRE’s conclusion. Serious concern about fish passage over this weir has been expressed by anglers, riparian owners and SWWA/NRA/EA staff over - at least - the last 30 years.

The main fish passage over the weir is on the right hand side of the medium filum . You suggest that a notch be cut in the weir at this point to allow fish migration even at low flows. However this part of the weir is not owned by the applicant. Ownership of the weir on the right hand side of the medium filum should be clarified and registered. And there is a need for clear and enforceable responsibility for the upkeep of this notch.

Yes I agree. The weir is unlikely to present a barrier to migration at migration flows, >2-3 cumecs. However, with abstraction of 1 cumec, the flow over the weir crest would be reduced. Without a notch to channel the flow there is a chance fish could be delayed.  
 

The weir leaks along its face. This could reduce the amount of water flowing through the notch. There is a need for registered and enforceable responsibility for maintaining the weir in order to maintain an adequate flow of water through the notch.

The notch would not need to take all of the HOF to function, it may need around 300l/s out of the 550 l/s. However, there would be an issue if the weir deteriorated and the depth in the notch reduced. A simple level in the notch would be the easiest to enforce.   
 

The EA guidelines advise that “..hydropower schemes incorporated within or immediately adjacent to a main channel weir and which would avoid depleting main channel flows, are more likely to be environmentally acceptable.”

Why is the installation not being located within or immediately adjacent to the weir? This might reduce the impact of the proposal on the fishery.

 

For this site the head drop at the weir is low (<1m). The additional head that makes the scheme viable is from the fall in the deprived reach of river. A minimum head of 1.8-2m would be required.  
 
 

Impact of the application on the already depleted reach

You note (page 3) that the original abstraction licence (14/46/05/0117) was revoked on 9th April 2009. Is there currently any control of water flowing down the leat? If not could this situation continue indefinitely?

I imagine that the sluice structure would control the flow in the leat.
 

For many years the mill leat has deprived the main river of an unknown and unregulated amount of water over a 470 yard stretch. I have not seen any historical record of the amount of water flowing down the leat. Therefore this application may exacerbate or ameliorate the current unsatisfactory situation.

As you know, the EA guidelines state that “The impact of the hydropower proposals on flow and ecology in the depleted reach is one of the key issues in permitting Hydropower schemes. “

Your report states that the proposal will “result in depleted flows in the bypassed section of main river”. It also identifies several fisheries issues.   

Figure 12 in your report shows natural flow down the river and the amount of water that would be diverted down the leat under two conditions:

  • One cubic meter per second
  • 50% of the natural flow  taken by the leat and the remaining 50% left to flow down the river

You recommend the first flow regime even though this would mean that more than 50% of the available water would probably flow down the leat between Q30 and Q60  

In a nutshell what you are recommending would mean that the turbine would not operate for about one month each year when the river is suffering from drought. During the remaining 11 months of the year about half of the available water would be diverted down the leat.

 
The turbine would shut down when the river was at a low summer level, not during drought conditions. It might be worth visiting the site when the river is at approximately Q90 (HOF) to get a better feel for the HOF.
It is not half of the available water, but up to half of the mean flow in the river.
 
So on average it would equate to this. 
 
At low flows, the turbine would be shut down. 
At typical average summer flows, the turbine would take approx. half the flow.
At medium to high flows, the turbine would take about a third of the flow. 
During a typical spate (not flood conditions) the turbine would take about a quarter. 
Very high flows, the turbine take would be <25%.       
 
  

I don’t think the association would welcome this scenario because of the impact on the amenity value of the depleted stretch.

Impact of the application on the amenity value of the depleted stretch

The EA defines a sustainable hydropower scheme as one that “maintains sufficient flow in any depleted reach to maintain the ecology and the fishery, including its amenity value.” (italics added). The EA are also obliged to consider the rights of fishery owners that may be affected.

Your report does not directly address the impact of the proposal on the amenity value of the fishery. You note (section 6.3,page 18) that it is difficult to quantitatively assess the impact of  the proposal on the habitat. But you suggest that the available habitat could be reduced by 3-7%. Any reduction in habitat will reduce the amenity value of the fishery. I think most people would be alarmed if a planning application reduced the size of their garden by an unspecified amount !

I do not agree with your estimate. If 50% of the water is diverted down the leat then the amenity value of the depleted stretch could be depleted by a similar amount – 50%

 
The impact on the fishery is not proportional to the flow split. The reduction in juvenile habitat may be in the order of 3-7% of the useful habitat. It would be less than this for the entire site as it is not all good juvenile habitat. If the leat is properly designed, this would introduce additional habitat that may well offset the few % reduction.  

Impacts on fish

Section 5 of your report describes the results from EA electrofishing surveys. All of these survey sites are upstream of the proposed site. The most recent survey – carried out in 2010 -is about 5km away. The nearest site (2 km) was last surveyed in 2007. According to EA guidelines “Where fish survey data to classify for WFD (Water Framework Directive)  above and below the site are not available, these will need to be provided by the developer to enable assessment against GES (Good Ecological Status ) to be made by the Environment Agency.” (my italics).  

You recommend that a quantitative electrofishing survey is conducted within the PDR (potentially depleted reach) to determine the existing state of fish populations. I must stress that this survey would be measuring fish populations in an already depleted stretch. The 470 yard stretch has suffered for many years from the loss of an unknown and unregulated amount of water.

In addition the situation might deteriorate even more under new licence conditions. Therefore there should be an agreed and enforceable series of post-implementation surveys, and an agreed set of enforceable mitigation measures.

Post operation surveys are fairly common for hydro schemes. However, we would need a reference point to establish if there is any impact. This is where pre-installation surveys can be useful. To be honest though, the natural variability within and between surveys would make it difficult to pick up a small change in fish abundance.      

You estimate that about 65% of the depleted stretch provides spawning and good quality juvenile salmon and trout habitat. The remaining 35% is deeper water and is known to hold adult salmon and sea trout. It is reasonable to expect that any further reduction in flow will have a greater impact on the shallow areas – the 65% of the stretch that supports juvenile fish.

You quite rightly point out that any abstraction should not lower water levels to such an extent that it interferes with fish migration. At the moment you report that three of the riffles in the depleted stretch are deep enough to allow upstream migration. But you express concern about Riffle#2. You recommend channel narrowing at this point. It is important to consider possible future deterioration in the remaining three riffles, and the possibility of new areas of shallow water developing along this stretch in the future. Therefore there should be an agreed and enforceable series of post-implementation depth surveys, and an agreed set of enforceable mitigation measures.

 
 I agree, rivers are dynamic and things could change in the future.  Depth surveys would be useful. 

Redd counts

The depleted stretch may be a salmonid spawning area. You recommend a redd count this winter. A one-off survey is inadequate. Salmon spawning varies from year to year. The EA may have records going back over many years of spawning activity in the depleted stretch which could be used to address this question.

We suggested redd counts if the EA did not already have the data.

It is important to consider possible future deterioration in spawning potential. Therefore there should be an agreed and enforceable series of post-implementation redd surveys, and an agreed set of enforceable mitigation measures.

Licence conditions and enforcement

You note (page 3) that the original abstraction licence (14/46/05/0117) was revoked on 9th April 2009. One of the conditions of that licence was that abstraction should cease when flows at Gara Bridge fell below 0.37 cumecs. How was this parameter measured at Gara Bridge? Did the EA experience any difficulties monitoring compliance with the conditions laid out in abstraction licence (14/46/05/0117)?

 
I am not sure how this was measured or if there were compliance issues. 
 

A clear description of the failsafe method(s)

  • used in the control and monitoring system to ensure that flow in the depleted reach is controlled and monitored
  • and data recorded to demonstrate compliance with licence conditions

would help to reassure the AFA that a new abstraction licence would be enforceable

Consultation to consider the impact of the application on the amenity value of the depleted stretch

I’m sure the AFA would welcome the opportunity to hear more about the proposed abstraction regime and the ecological impacts of the application. This would enable them to judge the impact of the proposal on the amenity value of the depleted stretch. We would be willing to host an open evening at a suitable local venue for our members and other interested parties. It would be useful if you could send me your report in digital format so that I can circulate it to our members.

 
I will email the report shortly.
 
 
 

Thank you again for inviting me to the meeting.

Best wishes

Paul

Paul Kenyon

Chairman and trustee Avon Fishing Association