Agenda item

(1)             Mr Paul Kent from Southern Water gave a presentation on Southern Water’s response to the Winter 2013/14 floods. The accompanying slides have been incorporated with the agenda papers on the County Council’s website:

 

(2)       Mr Kent’s presentation covered Southern Water’s role in flood management, the impact of the 2013/14 flooding, general improvements such as flood alleviation schemes, infiltration reduction and total care plans. He also addressed Southern Water’s role in the coming Winter, bearing in mind that the water levels were already higher than they had been at this point in 2013.

 

(3)       Mr Kent said that Southern Water engaged with Lead Local Authorities such as KCC, the District Councils, the IDBs, the Environment Agency and local communities in order to develop holistic solutions to flooding problems instead of working in isolation as had been the case in the past.  An example of close work with community organisations was that undertaken with the Stour and Nailbourne River Management Group. Southern Water also participated actively as a member of the steering group on flood and coastal erosion projects and was involved in Surface Water Management Plans.

 

(4)       Mr Kent moved on to consideration of the Winter 2013/14 floods which had first impacted with the St Jude storm event of 28 October 2014 through tidal flooding, particularly in the Dover area where the sea wall had been breached.  As the Winter progressed, the problems faced by Southern Water were the same ones faced by local authorities. There had been power outages as a result of trees and cables falling down, pluvial and fluvial flooding, tidal flooding.

 

(5)       By far the biggest issue had been that of groundwater flooding, particularly at Nailbourne and Petham.  This had been a very protracted process which had started in the New Year and, in some cases, lasted into May.  The problems created by groundwater filling the sewage system were usually alleviated through the use of tankers.  There was only a limited number of tankers that could be used in the South East (some 120 in total), and they were limited by the volume that they could take out of the sewer.  This meant that over pumping needed to take place in order to alleviate sewage discharge.

 

(6)       Mr Kent said that the response had been 24 hours a day at a peak cost of £150k per day.  It had involved 330 staff and the total cost to Southern Water had been in the region of £15 – 20m.  This money had come out of existing budgets rather than being charged to existing customers.

 

(7)       Mr Kent went on to give some examples of issues that Southern Water had tackled.  He said that one of the key priorities was to address those areas that were known to flood (particularly internally). These were delivered following a cost benefit analysis to those properties where the cost of protection was lower than that of the damage caused to them.  In the five year period from 2010 to 2015 a total of 46 properties would be protected from internal flooding at a total cost of £7.5m.

 

(8)       Another important area of work was infiltration reduction.  Progress had been made in reducing the volumes of water that had got into the groundwater system. Over the previous few years, Southern Water had inspected 10km of sewers and 250 manholes.   In 2014, 3.5km of sewers had been repaired, complementing the 4km of repairs in previous years.

 

(9)       Mr Kent said that Southern Water operated 40,000 km of sewers in the South East which were regulated by 2,400 pumping stations.  These were now the subject of a total care package whereby the pumping stations were inspected and everything that would shortly need replacing was done at the same time, rather than leaving parts of it to a later date. This had resulted in a dramatic improvement. To date, 1,000 had been repaired, having been prioritised in 2013.

 

(10)     Mr Kent then gave examples of improvements that had taken place at Bishopsbourne and Bekesbourne before turning to the flooding issues which had arisen three times in the previous 14 years in Canterbury Villages along the Nailbourne.  It had also been necessary to tanker and over pump during three other winters during this period.  Water along this river from the Village of Barham and those to the north was pumped pumped into Newnham Valley WTW.  During the Winter floods of 2013/14, the tankers had been deployed in this area but had quickly run out of capacity.  Over pumping had therefore been installed at Barham, Bishopsbourne, Patrixbourne, Bekesbourne and Littlebourne.  Each of these locations had discharged between 20 and 50 litres per second.  Even so, there had still been bottlenecks at some of these locations where tankers had needed to assist.  This had also been the case in Bridge.

 

(11)     Mr Kent said that the southern part of the Nailbourne between Elham and Ottinge was where water flowed towards the pumping station in Hythe from where it was discharged into the sea.  This part of the catchment had not suffered as badly and there had only been two events over the past fourteen years. One of these events had been during the 2013/14 Winter Floods. Groundwater infiltration had led to restricted toilet use.  It had also been necessary to protect the source of affinity water at Ottinge by over pumping.  Southern Water would be undertaking some further work before the winter of 2014/15 including jetting, root removal, sealing/covering of manholes, and the protection of Water Farm.

 

(12)     Mr Kent went into detail about over pumping, which was a last resort to be used when groundwater levels were very high that they were causing surcharge of the sewerage system, causing flooding and restricted toilet use.  The water pumped out of the system was 90% clean water rather than the type of sewage that was usually found in the system.  Permission was always sought from the Environment Agency before any over pumping commenced.  The quality of the water was (due to the way it was treated) similar to some of the effluent that was found in the WTWs.  This ensured that any adverse impact on the watercourse was minimal and of a purely temporary nature.

 

(13)     Mr Kent described the Bio –treatment units, showing examples of units which had been delivered in Barham.  They worked by pumping sewage across the top of the tanks and were filtered through bacteria which grew on the plastic media, treating the sewage.  This process removed some 30% of the polluting load before discharge into the water course.  This represented a big improvement over past practice which had seen sewage pumped direct into the water course.

 

(14)     Mr Kent described two other methods of waste water treatment which had recently been utilised. These were suction screening and effluent screening.  The main problem in respect of the latter was that the bags filled within half a day and were not re-usable.  Consequently a new system had been developed with the supplier which did allow the bags to be used again.

 

(15)     A great deal of time and effort had been spent on sealing the fluid along the Nailbourne. This had been effective as demonstrated by the graph entitled “Nailbourne Improvements”.  During the winter of 2012/13, the pumps had needed to be turned on when the groundwater level had reached 78m AOD and had been turned off again when it had dropped to 75m AOD.  In 2013/14, the pumps had been turned on at 81m and off again at 80m.  This suggested that the sewage had been sealed and had been able to withstand a much higher level of ground water.

 

(16)     Mr Kent said that Southern Water had often been asked how it measured success.  He said that this would have been retrospectively achieved if over pumping had only been needed in 2000/01 and 2013/14 and not on the other three occasions in between.  He was hopeful that the investment recently made by Southern Water would result in over pumping not being needed in the coming winter.

 

(17)     At Petham Bourne, there had been problems in 2000/01 and again in the previous winter.  Petham Bourne did not have a natural bed and therefore formed its own bed as it began to flow. The biggest problem had been the overflowing manholes in the grounds of the Stiener School which had resulted from water infiltration into the system. The manholes had been sealed and the pumping station had been refurbished with new pumps being installed.   This meant that with a threefold capacity, pumping could now get rid of the water three times more quickly than before.  Mr Kent said that he did not anticipate flooding at this location in 2014/15 but, if there was, it would be far less severe than in 2013/14.

 

(18)     Mr Kent said that in Five Oak Green there had historically been a number of flooding instances as a result of the unreliability of the Larkfield pumping station.  Southern Water had spent £300k refurbishing it and it was now working satisfactorily. In the winter of 2013.14 there had been other issues. The surface water system had suffered blockages by tree roots, whilst significant amounts of grit and sediment had built up in the attenuation tank.  These issues had been fully addressed, as had the issue of the restrictions on surface water flowing into a ditch. This latter issue had seen a collaborative solution involving the EA and the local IDB. 

 

(19)     Mr Kent said that there had been significant flooding in Danvers Road/Barden Road in Tonbridge.  This had mostly been due to the capacity of the road drainage. This was not the responsibility of Southern Water but the company had assisted by jetting the surface water sewers to remove sedimentation.

 

(20)     Mr Kent briefly summarised work in other locations such as Alkham Valley (garden flooding and restricted toilet use), Preston and Elmstone (replacement of manhole covers), Ickham and Wickhambreaux (protection of Drill Lane pumping station from fluvial flooding).

 

(21)     Mr Kent then set out how Southern Water was preparing for the winter of 2014/15.  Consideration of the previous winter’s lessons had now taken place and the outcome was that every area’s potential problems had been centrally identified in Operational Incident Plans, which would assist greatly in the event that tinkering or over pumping would need to be deployed.  Southern Water continued to work with the Management Group for the Nailbourne to ensure continuous improvement through the Infiltration Reduction Plan (IRP).  This had come about because Southern Water had permission from the EA to over pump from the sewers into the watercourse provided that it set out how it intended to deal with the infiltration issue.  The IRP was being shared with other parties, including the Management Group which demonstrated that progress was being made.  Other work involved protecting properties through the installation of non-return valves, refurbishing pumping stations or replacing pumps (as at School Lane).  This was essential as the data showed that water levels were as highj as they had been 6 weeks earlier in the calendar year of 2013.

 

(22)     Mr Kent moved on to the topic of flood protection methods for properties. In some properties, the cost of providing complete protection could be as high as £1m.   In these instances, flood mitigation methods were deployed.  These included garden re-profiling, the installation of water tight doors, airbrick covers, purpose-made flood barriers such as wooden gates or non-return valves to prevent flood water flowing back into the property from the main sewer.   These were not seen as a permanent solution as they could not permit water from the property to escape once the sewer was blocked. They were fitted on a priority basis and only when they would provide benefit. This meant that they should not be installed if the outcome was that the flooding problem was simply transferred to the neighbouring property.

 

(23)     Mr Vye asked whether Southern Water could provide the Members of the Committee with a list of the improvements carried out in order that they could make any pertinent comment on the priorities identified.  He then said that there were three concerns for Southern Water. These were reputational damage, legal requirements and financial considerations.  He then asked what Southern Water’s investment plans were for the solution of the basic problem, which was lack of capacity in the sewer due to water infiltration.

 

(24)     Mr Kent replied that Southern Water was well aware of the risk of reputational damage. Its legal responsibility was to operate a sewage system that was fit for purpose.  Groundwater infiltration was dealt with using the Best Available Technology Not Involving Excessive Cost (BATNIEC) Principle.  This meant that it would not be possible to replace the entire system because this would cost between £50 – 60m and there were other competing major priorities. Had all the current measures been in place from 2000 onwards, three of the flood events would probably not have required tankering and over pumping, however the events of 2000/01 and 2013/14 would still have needed  these measures because Southern Water could not invest against such extreme events.  In fact, Southern Water’s flood defence measures were effective for 98/99% of the time.

 

(25)     Mr Vickery-Jones asked whether the biotanks were making a meaningful contribution.  Mr Kent replied that analysis showed that there had been 30% reduction in the polluting load going back into the watercourse.  Trials would be taking place at Aylesford WWTW to fully identify their effectiveness under test conditions.  Southern Water had also lent some of its biotanks to Thames Water as they, too believed that they represented an effective way forward.  Furthermore, the Environment Agency had assessed the quality of groundwater which had been through the biotanks and found it to be superior to water which had simply been over pumped without any further treatment.

 

(26)     Mr Vickery-Jones then reported that he had attempted to contact a Waste Water engineer but had been told that there was a corporate instruction from Southern Water that engineers should not respond to Councillors. He had been informed two weeks earlier that Southern Water would return the call to Canterbury CC’s Engineering Department but no response had yet been received  Mr Kent replied that if an individual rang Southern Water’s 0845 number they would get a response at any time of the day or night (24/7).  If the issue was identified as requiring immediate attention, there was sufficient capacity (including engineers being on standby) for this to happen.  If, however, someone was asking the backroom staff for a response on a technical issue, this would be more problematic.  He agreed that a response should have been made to the original call (as would normally be the case). He undertook to follow up the individual incident described.

 

(27)     Dr Eddy noted that the slide on the Total Care Plans stated that they had commenced in 2013 “stripping and inspecting every pump and valve – repairing/replacing where necessary.”  He asked how many had been dealt with in this way so far.  He then asked the more general question of what contingency plans Southern Water had in the event that groundwater levels continued to rise, potentially exceeding those of the previous winter.

 

(28)     Mr Kent replied that Southern Water had 2,400 wastewater pumping stations.  Just over 1,000 had been completed to date. These were the highest priority pumping stations.  In response to the general question, monitoring of groundwater levels was taking place twice each week.  Statistical modelling was also taking place to identify when pumping might need to commence.  This model was updated on a weekly basis. Once the trigger level was reached, Southern Water would begin to talk to its contractors and partners so that pumps and tankers could be employed at the right time with the minimum of delay.  Meanwhile standby rotas were being developed to ensure that sufficient numbers were available when they were needed.

 

(29)     Mrs Blanford said that maintenance did not appear to be a high priority for Southern Water.  She asked whether there was a programme to put things right before a major flooding event occurred.   She said that another concern was that the EA often complained about the quality of water being pumped into the River Stour.

 

(30)     Mr Kent replied that Southern Water did carry out a lot of maintenance work.  There were 40k km of sewers, 2,400 pumping stations, 368 WWTWs. Southern Water annually spent some £20 – 30m on maintenance on sewers, £15 – 20m on pumping stations and £20 – 30m on WWTWs.  In terms of water quality in the Stour, it was the EA which granted the permit to Southern Water, which was not allowed to simply discharge into the river without permission.

 

(31)     Mr Pearman said that the Met Office’s weather projections were not promising. It was essential that the water level data was accurate.  He said that the Emergency Planning Committee in Edenbridge would have been far more prepared at this time in 2013 if it had been aware of the water table levels at that time. They had learned during the winter that responding to EA alerts needed to be supplemented by planning before the alerts were issued.   He asked whether there was commonality between the water table levels identified by the EA and Southern Water. 

 

(32)     Mr Nunn said that the data was jointly complied by the EA and Southern Water.   He added that since the 2013/14 flooding events, a great deal of additional maintenance work had been carried out by all the agencies.  As a result, preparations were in advance of where they had been a year earlier.  Although there had been a relative dry spell in September/October, groundwater levels were still higher than he would have liked them to be.  The EA would be undertaking modelling on a daily basis to establish actual rainfall and groundwater levels as well as filtration rates.  Meanwhile, all agencies were on a heightened state of alert. The EA had already prepared its Christmas “double up” rotas.  He agreed with Mr Pearman that organisational preparedness needed to be communicated to the public and volunteers on the ground at the appropriate time.

 

(33)     The Chairman commented that the Met Forecast was only available on mobile phones rather than on iPads.

 

(34)     Mr Kent said that it was essential that all organisations were prepared and that none of them attempted to work in isolation.

 

(35)     Mr Hills said that the work of the EA, Southern Water and the IDBs was very praiseworthy.  The need was to ensure that communication between them and with the District Councils was effective in order to promote pre-planning.  For example, there was a big capacity problem at the sewage works in Littlestone where there was nevertheless, a 400 house development plan.  

 

(36)     Mr Kent said that Southern Water recognised that this was a period of greater extremes of weather conditions.  These were catered for in the design standards.  An example of this was that whenever a new sewage pipe was laid, it was substantially bigger than it would have been five years earlier. 

 

(37)     Mr Kent added that Southern Water had a duty to allow all property owners to connect into the sewage system.  This gave Southern an imperative to recommend to planning authorities where this connection should take place.  In recent weeks, consideration had been given as to how this work could be undertaken more speedily and effectively.

 

(38)     RESOLVED that:-

 

(a)                      Mr Kent be thanked for his detailed and informative presentation;

 

(b)                      the content of the presentation be noted, together with the letter  from Southern Water set out in the Appendix to the report; and

 

(c)          copies of the presentation be sent to all Members of the Committee.