Posted by: westlancashirerecord | July 7, 2016

How Much More Flooding In Burscough?

The WLBC Borough Solicitor Terry Broderick terry-broderick received this letter from Burscough resident Gavin Rattray, below, in June.

“Dear Mr Broderick. I recently spoke to Bernie Webster and a group of residents from Crabtree Lane about the severe flooding which has happened to their houses three times recently. Like sewer flooding in the centre of Burscough, their flooding has become an almost annual event, though in this case it is surface water and not caused by UU yet! They contacted WLBC about this problem years ago and as a result there are pictures on WLBCs website of the widespread and deep flooding that occurs to them. However, WLBC have so far have shown no interest in solving the problem, except I believe, to say that their budget has been cut and direct Bernie to the environment agency.

“Their houses are adjacent to the railway line which crosses Crabtree Lane. The source of the flood water is a watercourse fed from two main watercourses that run across Yew Tree Farm and exit across Higgins Lane. Given that a planning condition of stage A YTF development requires removing surface water from the sewers and adding it to the watercourses; there would inevitably be an increase in flooding in Burscough due to building on YTF. As your letter in 2012 (attached) played such an important part in reassuring so many residents that building on the massive Yew Tree Farm greenbelt site, “will not be allowed to make it [flooding in Burscough] worse”. Do you still stand by your statement? And, if so, what measures are you going to put in place?” your2027

Mr Rattray received this reply from WLBC Planning “Thank you for raising the concerns of Mr Webster and his fellow residents of Crabtree Lane with the Council. Your email to Terry Broderick, the Borough Solicitor, was passed to me to respond to given it is a planning matter related to the Yew Tree Farm development. You state in your email that “The source of the flood water [at Crabtree Lane] is a watercourse fed from two main watercourses that run across Yew Tree Farm and exit across Higgins Lane.” You then go on to link this apparent source of current flooding to increased levels of flooding in Burscough in general because “Given that a planning condition of stage A YTF development requires removing surface water from the sewers and adding it to the watercourses; there would inevitably be an increase in flooding in Burscough due to building on YTF.”

“As you will recollect from your participation in the Local Plan preparation and its examination, and from various correspondence with Council officers in recent years, the key planning test in relation to a development’s impact on flooding is that the development should not make the situation worse. The development cannot be required to improve the current situation, although it is hoped that the measures being required at Yew Tree Farm will reduce the risk of flooding from sewers in Burscough in general by removing a part of the surface water run-off currently entering the sewer system in Burscough. Specifically with regard Crabtree Lane, if the watercourses are the source of surface water flooding (presumably at times of very high rainfall), reducing the risk of sewer flooding does not help their specific situation. However, it does not follow that the improvements required as part of the Yew Tree Farm development to redirect surface water from the sewer system would make the situation at Crabtree Lane worse.

“While the Yew Tree Farm development bag1 would be required to manage the surface water drainage not only from the site itself but that redirected from the sewer system, it does so by providing attenuation of surface water on-site, so that even when there are high levels of rainfall, the surface water drains into the watercourses crossing the site at a greenfield run-off rate (i.e. as it would when the site is undeveloped). This means the provision of surface water attenuation on-site would be unlikely to allow the surface flooding at Crabtree Lane to be made worse (if the watercourses in question are the source of flooding) and, in fact, the situation could be improved as the run-off into the watercourses, even at times of high rainfall, would be attenuated by the new drainage infrastructure at Yew Tree Farm and so run-off into the watercourses at peak rainfall times might actually be lower than they are currently.

“Therefore, while the Council cannot remove the risk of surface water flooding at Crabtree Lane, or in Burscough in general, nor require the developer of a site such as Yew Tree Farm to do so either, the measures we can insist upon as part of the development can ensure the situation is not made worse and may actually result in improvements. I hope the above addresses your query”.

Mr Rattray replied “Thank you for your email on behalf of Mr Broderick. The YTF planning application 2015/0171/OUT states that the surface water from Lordsgate Lane and Admiralty Close will be diverted from UUs combined sewer network onto Yew Tree Farm surface water attenuation system. A BPC drainage report, a copy of which was sent to WLBC, highlighted the problem that the attenuation system planned for YTF has insufficient capacity. yew5

“The sewer mitigation planned is less than the highest early morning and evening sewer flows from the development. If you design a water attenuation system for 56.7 l/s (see clause 5.4 in the drainage report) and actually put approximately 80 l/s through it (63.7 l/s + 15.5 l/s); then in a rainfall event (see clause 6.2) it will be full 40% sooner than designed. At which point, a flow of 80 l/s, which is significantly higher than the predevelopment Greenfield rate (63.71 l/s), will flow to the watercourse on YTF, increasing the downstream flood risk for Burscough’s residents such as Mr Webster.

“In addition, because farmland absorbs more water than developed land, as crops use the water and encourage evaporation. Converting a large part of the farmland at YTF to homes and roads will increase the annual quantity of water run-off from YTF and drained into the watercourses; raising the water table in the downstream area and increasing the flood risk. Adding the surface water flows from Lordsgate Lane and Admiralty Close, which were previously drained using UUs sewer network, to the same watercourses will also have the same negative effect.

“Once the development is built, whenever Burscough suffers heavy rainfall during early morning or evening peak sewer flows the mitigation will be 15.5 l/s (clause 6.4) and the additional sewer flow will be 26.71 l/s (see clause 6.3). Therefore, the sewer flow will be approximately 11 l/s (26.71 l/s – 15.5 l/s) more than the predevelopment rate, which will increase the risk of sewer flooding, because any network increase would (see first bullet clause 4.7).

“As WLBC have granted outline planning permission to a scheme that will significantly increase the annual water flow into a watercourse known to flood widely with 40% of that flow to be effectively unattenuated; and have also allowed the scheme to increase the peak flowrate to UUs undersized sewer network by 11 l/s. I fail to see how 2015/0171/OUT, “will not be allowed to make it [flooding in Burscough] worse”.

“Does Mr Broderick still stand by his statement? And, if so, what measures are WLBC going to put in place?”


Responses

  1. Excellent work, Mr Rattray. I look forward to Mr Broderick’s reply.


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