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Amplitude modulation conditions approved  

Credit:  Noise Bulletin June 2011 Issue 53 ~~

In what is expected to be the final chapter of the long running Den Brook wind farm ‘war’, both sides have claimed success in the High Court. The wind farm gets the go ahead – but stringent amplitude modulation conditions are confirmed and likely to be used elsewhere.

The Den Brook wind farm was first mooted in 2004 and has been in and out of the courts ever since, a saga that was covered in the recent four hour BBC Windfarm Wars documentary. Grounds for objection were gradually whittled away leaving amplitude modulation (thumping) as the only issue in dispute.

Developer RES said noise would not be audible or a problem. Objector Mike Hulme was not convinced and wanted a legally-watertight condition that could allow the wind farm to be sanctioned if it produced amplitude modulation.

In the final stages, Hulme’s acoustic consultant Mike Stigwood proposed specific conditions, which were adopted in part, leaving some ambiguity requiring the final appeal.

Hulme technically lost this appeal with the court stating that while the condition was badly worded (suggesting that all the operator needed to do was measure and assess noise, not treat it), the court said the condition could be inferred as meaning noise would also have to be stopped.

Hulme says this was the protection against noise nuisance that he had been seeking from the start: “RES now has to meet the unprecedented and significant reduction of the noise limits in the event of amplitude modulation from the wind farm.

“In coming to their judgement the Lords have not only set in stone the parameters of the Den Brook amplitude modulation condition but also cut off any further opportunities for RES (they have tried) to redefine those parameters through the scheme required by the noise condition. It is exactly what I set out to achieve.

“Hopefully, others will now be able to make use of, and benefit from, this amplitude modulation condition precedent for their own cases.”

Mike Stigwood told Noise Bulletin: “I devised an excess amplitude modulation condition based on my findings and measurements at other wind farms that was worded simply and made an exceedence a breach. It was a simple stand- alone condition.

“The Inspector decided to add a section to the condition requiring that on receipt of a complaint the wind farm operator must investigate and measure the excess amplitude modulation, omitting the wording which made it clear that excess was a breach. Thus it changed from ‘it shall not occur’ to ‘if it does occur then you must measure it’. He did keep the definition of excess amplitude modulation which was important.

“The important outcome is that if excess amplitude modulation occurs, it is a straightforward breach of the consent and can be addressed by enforcement action. It also rather endorses the definition itself and at last residents have a recognised form of words that protects them against excess amplitude modulation from modern wind farms.”

The appeal decision went into much detail about noise, and restated developer RES’s objections from previous inquiries against noise conditions on the grounds that excessive amplitude modulation is rare and conditions for amplitude modulation are not recommended in Etsu guidance.

Inspectors rejected these arguments as misleading: “If amplitude modulation is unlikely, then it is equally unlikely that it would be necessary to enforce the condition. On the basis of the evidence I have heard I am satisfied that the phenomenon is not fully taken into account in Etsu and the condition imposed is of a precautionary nature … in my opinion the imposition of conditions is both necessary and reasonable.”

Another Lord commented: “There is no doubt that the relevant conditions could and should have been drafted with greater precision but, read in the context of the planning permission as a whole and against the background of the objectives set out in the inspector’s report, it is clear that the intention was that the condition 20 limits should be complied with.”

The wind turbine industry, through Renewable UK, does not like the move by inspectors to impose conditions: “The problem for the industry is that there is currently insufficient knowledge to be able to draft such a condition or, at least, to draft one which does not cause difficulties for the industry in the future. This lack of knowledge has not stopped opposition groups from drafting their own condition. This condition is completely untested and may pose a serious barrier to the continued development of onshore wind power.” It has launched research to frame an industry-agreed condition).

The conditions at the heart of the dispute – and endorsed by the High Court are:

Condition 20: At the request of the local planning authority following the receipt of a complaint the wind farm operator shall, at its expense, employ a consultant approved by the local planning authority, to assess whether noise immissions at the complainant’s dwelling are characterised by greater than expected amplitude modulation. Amplitude modulation is the modulation of the level of broadband noise emitted by a turbine at blade passing frequency. These will be deemed greater than expected if the following characteristics apply: a) A change in the measured LAeq 125 millisecs turbine noise level of more than 3dB (represented as a rise and fall in sound energy levels each of more than 3dB) occurring within a 2 second period and b) the change identified in (a) above shall not occur less than five times in any one minute period provided the LAeq 1 min turbine sound energy level for that minute is not below 28dB and c) the changes identified in (a) and (b) above shall not occur for fewer than six minutes in any hour.

Noise immissions at the complainant’s dwelling shall be measured not further than 35m from the relevant building, and not closer than 3.5m of any reflective building or surface, or within 1.2m of the ground.

Condition 21: No wind turbine shall generate electricity to the grid until the local planning authority, as advised by a consultant approved by the local planning authority at the expense of the operator, has approved in writing a scheme submitted by the wind farm operator providing for the measurement of greater than expected amplitude modulation immissions generated by the wind turbines.

The objective of the scheme (which shall be implemented as approved) shall be to evaluate compliance with condition 20 in a range of wind speeds and directions and it shall terminate when compliance with condition 20 has been demonstrated to the satisfaction of and agreed in writing by the local planning authority.

Full judgement: www.bailii.org/ew/cases/EWCA/Civ/2011/638.html

Source:  Noise Bulletin June 2011 Issue 53

This article is the work of the source indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.

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