Open letter to Scarborough Borough Council Planning:
With regard to the proposed residential development to the south of West Garth, Cayton.
The developer has made proposals that drainage from the development will be completed by use of attenuation tanks as the preferred method.
It is clear that alternative methods would hold little or no value to the developer because of the financial implications.
Water harvesting would increase the cost per unit considerably (a cost that they would be unlikely to recover from any purchasers) and the provision of retention/detention ponds would use up valuable building plots thus making the development of this particular plot of land unviable. (The siting of any ponds would have to be contained within the land they own/develop).
What the developer proposes is by definition a Sustainable Drainage System. Having made contact with the Construction Industry Research and Information Association, it is clear that the developer’s proposal is experimental to say the least.
There is little information based on case study to support the proposal, indeed the general use made of attenuation tanks is based in urban areas on non residential projects as one off developments such as shopping centres, schools etc, which already have good drainage systems in place and where the use of such tanks is to prevent the systems becoming overwhelmed by the additional run-off water being otherwise uncontrolled or limited.
The case studies provided by the information association involving residential projects are entirely based on retention/detention ponds and a variety of similar features etc. The proposal of the developer is plainly not suitable for this location based upon its geological composition, lack of infrastructure and environmental impact.
By email the information association have responded to our request for guidance.
“Generally speaking it should be possible to manage surface water at or very near the surface rather than complete reliance on attenuation tanks – these do not need to be large detention basins or ponds and could include a small collection of features. Attenuation tanks can be a part of the solution and should not be the only approach used.”
It is clear that because of the poor drainage of the land which is recognised by everyone involved (including the developer) and the financial issues as above the developer cannot use alternative methods and is proposing what can only be described as a untried system that they ‘believe’ will work but for which there is no substantial supporting evidence other than speculation.
The requirement for a working model by both Yorkshire Water and the Environment Agency demonstrates their real concerns for the viability of the project.
The drainage system requires ongoing maintenance. This one would be no exception and it is clear reading the Construction Industry Research and Information Association documents that would not remain with the developer and would become the remit of either the Borough Council or a Third Party (Yorkshire Water).
There is little governing legislation regarding this matter although the information association recommend that a Maintenance Framework Agreement is signed prior to any development being started. The drainage system must be approved by the council and any other parties such as Environment Agency and Water Authority prior to any undertaking being made.
Whether the maintenance is passed or vested to the council or a third party agency the developer has to provide sufficient funds to ensure the adequate maintenance of the project for the next 30 years either by a lump sum or and agreed annual inflation proof payment. How can this be managed on such an experimental proposal.
It is clear the developer’s proposal goes against the ethics of Sustainable Drainage System. They propose to create a storage system because the land is clearly unsuitable to build on without.
The system is not a tried and tested one and unlike the use of attenuation tanks within an urban environment does not have substantial drainage infrastructure already in place. This system proposes the release of stored water into a system of, at best, ill-maintained ditches and culverts: a system that cannot be improved because of the poor lie of the land into which it proposes to dispose of the water.
The validity of this proposal must be seriously questioned. It is not environmentally acceptable to simply hope that any future flooding takes place further down stream nor is it acceptable that a system such as this be used in these circumstances contrary to the guidelines of acknowledged experts.
Green Croft Gardens