Agenda item

Discharge of condition 12 (foul drainage) from planning permission SB/14/02800/OUT - erection of 157 dwellings with associated access from Main Road, parking, open space and landscaping.

Permit.

Additional information was reported on the agenda update sheet identifying the connection into the mains sewer and location of the associated manhole with substitute plans.

The following members of the public addressed the committee:

Mrs A Tate – Parish Representative

Mr M Evans – Objector (provided information read by Mrs S Seabrook)

Mr J Child – Objector

Mr R Seabrook – Objector

Mr R Reay – Agent

Mr J Brown – Chichester District Councillor

The Chairman commented that further to the concerns of the objectors and Councillor Jonathan Brown, in relation water management, information was required from Southern Water and introduced Mr Csatlos, a Senior Project Manager from the company.

Mr Csatlos explained his role to provide capacity for new developments.  In addressing the points raised by members of the public whom had addressed the Committee, Mr Csatlos began by explaining that there had been a burst rising main in the previous year due to the unexpected cold weather which had caused operational problems with both water and sewerage infrastructure.  Since this time a number of additional measures had been taken to prevent reoccurrences.  This scheme was to address capacity for the housing development and not operational matters, and similarly at the treatment works the scheme was to deliver infrastructure capacity and not treatment capacity.  Treatment capacity matters are dealt with by way of the local plan level and not on an individual site by site basis, and at site level the capacity is delivered with the understanding that the treatment capacity is already in place.  Mr Csatlos explained that he could not comment with regards to how surface water is being dealt with, but the matter in question concerned foul discharge and he was able to take questions on out flows from the development.  Mr Csatlos further commented that with regards to the lack of information, if that was the perception of Southern Water, he would like to apologise on behalf of the company.  Mr Csatlos added that revision of the modelling criteria was based on defined methods, following recent studies.

The Chairman responded that he was not clear of the reasoning for Southern Water delivering a different scheme to that previously agreed, also without consultation, and asked if Mr Csatlos could elaborate as to why this scheme was needed and how it was an improvement.  Mr Csatlos explained that the developer had submitted a section 98 application and following this Southern Water had produced a study and modelling report which outlined what was required.  The modelling report was produced at the beginning of 2016 and the modelling criteria had since changed the LASSO Report and 21^st Century Capacity Drainage Report 2017, which had highlighted errors in the previous assessment. The most significant finding was in relation to the misconnection of surface water to the foul system.  The previous calculation for surface water ingress had been 4 metres squared per property, but had since been revised to 1.4 metres squared per property.  The average number of people in a property was also previously 2.8 but was revised to 2.4.  The water usage was also reviewed and revised from 135 to 125 litres per person per day.  A further factor which resulted in a reduction in the flow criteria impact for new developments was the existing catchment which was assumed to have 40% infiltration.  This rate was based on the fact that some pipework was many years old, even Victorian, but on new development sites all pipes were new therefore surface water ingress was not anticipated at that rate, and surface water infiltration from new sites was applied at 10%.   

The Committee asked for further information regarding who has responsibility for the treatment works, how is treatment different from capacity and the reason for changing modelling criteria.  Mr Frost explained with regards to the respective roles, Southern Water is the statutory undertaker with responsibility for infrastructure to convey waste water to the treatment works.  Mr Frost reminded the Committee that Mr Csatlos was present to answer questions and demonstrate that the scheme which Southern Water had implemented was an appropriate scheme to deal with waste water from the Priors Orchard development and an adequate replacement for works which were approved through discharge of condition a few years ago.  Mr Frost confirmed that this was the question the committee must consider in order to decide whether to discharge the condition.  This was a technical matter and the Committee should be able to rely on the advice from Mr Csatlos from Southern Water.  Mr Frost added that the site was in the Neighbourhood Plan and part of the Council’s strategic housing requirement given to Southbourne as included in the Local Plan and his understanding was that there was sufficient headroom at the waste water treatment works. 

The Chairman commented that with regard to the Neighbourhood Plan, the development was accepted with the understanding that the required works would be completed and the request was now to change the information discharged by condition, for reasons for which were not fully understood.  Mr Whitty confirmed that the waste water capacity was not a question for the Committee as that had been previously agreed by the grant of permission for the Priors Orchard development. The consideration was whether or not the current proposals were sufficient to convey the water to the waste water treatment works.  Southern Water had not needed to resize the pipe or upgrade the pumping station as originally estimated, as the revised modelling (required by Ofwat) and on site testing had indicated that there is less water flowing through the existing pipework than previously estimated and more existing capacity in the pumping station.  Therefore, at this time there was no requirement for an upgrade, although that may change in the future.  In relation to the pumping station capacity, Mr Whitty identified that it had been estimated that the pumping station was operating at 45 litres per second in the original assessment, and the original programme of works specified this was upgraded to 49 litres per second. Yet when the pumping station was tested it was found there was existing capacity for flows of up to 95 litres per second.  Instead, the updated assessment identified a requirement in a different part of the network for a storage solution. This had now been implemented.  With regard to the suggestion that the a decision be deferred to gain information from the Environment Agency, Mr Whitty explained that the Environment Agency’s remit did not extend to the network, as that was the responsibility of Southern Water.

During the discussion members debated the concerns raised by objectors and supporters including if the estimate of usage for each dwelling had taken into consideration the size of dwellings, and if the system would be fit for purpose.  Mr Csatlos confirmed he was confident that the modelling was correct, had used current data, and the system was fit for purpose.  Mr Csatlos also outlined further changes which supported the decision for reviewing the needs afresh and departing from the 2015 estimate.  The latest modelling report was completed in 2018 and a drainage area plan in 2017. These provided updated information regarding the flow through the system.  Additionally, a drop test was undertaken in the pumping station which confirmed upgrading was not required. The offsite tank to accommodate additional flow was adequate. In response to a question regarding the condition of the pipes, Mr Csatlos confirmed although the pipes were not investigated, the flows through the manholes and pumping station indicated the scheme for the development site was as required. 

Many members expressed reservations at the discharge of foul water from 159 dwellings into an 85 year old 6 inch clay sewer pipe already serving a popular 55 – plot campsite. The Southern Water representative emphatically stated that the results from their modelling clearly indicated that this was fully acceptable.

Mr Frost confirmed that the role of Southern Water was to assess and determine what was appropriate in providing infrastructure for this housing development and would not address pre-existing problems within the area.  Mr Frost concluded that the question before the Committee was whether based on the information provided that the scheme installed is appropriate to convey waste water from the Priors Orchard scheme and a decision must be based upon that.  Mr Frost added if the Committee refused to discharge the condition, the developer would have no option but to make an appeal, which would require the Council to mount a case and questioned what would that comprise of, as Southern Water were satisfied with the work they had completed. Therefore the only evidence would be local information and anecdotal concerns and it would be very difficult for the Council to demonstrate that the infrastructure was not fit for purpose.   

Following further comments from the Committee, a decision was taken to vote.

Recommendation to Permit agreed.