SuDS an enabler for development?
Graham Fairhurst, Independent Consultant and Chair Susdrain Project Steering Group
Having now had several insights into the way in which developers perceive the housing market and how NPPF and council planning policies are working, some fairly clear trends can be seen. As an engineer I might well dream of an ideal world with an optimised approach to planning which might push for development in the most sustainable locations (e.g. inner city/urban brownfield sites or New Towns where there is often under-used drainage infrastructure). However, market pressure to build new housing on the edges of urban areas and in villages is considerable and probably always will be. Many of these locations may also be supportable in sustainability terms.
Picture this scenario in the Britain of 2015:
District Council planners have worked hard to deliver a Local Plan which shows an adequate supply of housing land over the plan period. This Plan also contains policy that seeks continued development in a former mining town which is necessary to sustain other regeneration initiatives in this part of the District. The planners however realise that the new housing numbers cannot solely be delivered through this route because the market needs other, more attractive sites. The Plan has therefore designated a number of villages as Key Sustainable Settlements; this is because they already have schools, shops, doctors, and public transport services. However, many of these are places where drainage infrastructure is already stressed in terms of capacity. These locations often have very small diameter pipes, built in the post war period when the villages were taken off septic tanks. These pipes were intended essentially for wastewater/foul flows from the villages as they were at that time.. In the real world the villages have grown and the pipes now convey at least a proportion of the developed areas’ surface water as well. This leads to flooding, frequent operation of combined sewer overflows, or overloaded sewage treatment works and pumping stations (with excessive electricity consumption); Or it may lead to a combination of all of these. This is of course the responsibility of other parties, including the sewerage undertaker and regulators, and is often a lower priority.
Along comes our developer having studied the Local Plan, looked closely at the Key Sustainable Settlements and negotiated an option on a piece of land in one of these sites, which the Local Plan had also identified as a Rural Development Opportunity. Our developer works up a scheme for the site, also notes the requirement to deliver a certain percentage of affordable homes and submits the planning application.
Surprisingly, our Key Sustainable Settlement is now not so sustainable after all and the Rural Development Opportunity less of an opportunity! The sewerage undertaker is reluctant to accept new flows and is advising the planners so. At the same time, the Lead Local Flood Authority is expressing concerns and a local opposition group has formed, pointing out the flooding problems in the village. They weigh in with an objection to planning permission being given. The developer also takes a deep breath when the amount of Community Infrastructure Levy is worked out and allocated to the former mining town as this is the key area of infrastructure need within the District. Whilst nothing is available for infrastructure in this village.
This sort of problem can result in considerable delay for the developer who has to wait while the sewerage undertaker improves the sewerage system. But liquidity is a major factor in development dynamics and stalled sites are highly undesirable. Therefore our developer will often give-in and agree to a condition that they pay for, or carry out specified sewerage improvements themselves. These works can often be quite expensive, and also disruptive for the village. The costs will either reduce the viability of the development so that the developer then seeks to negotiate a reduction in the number of affordable homes to be provided as part of the development or instead passes these infrastructure costs on to the house purchasers, further reducing affordability .
(For a council, a stalled site within its plan may increase pressure on housing delivery and the risk of development proposals coming forward elsewhere. These sites could be less desirable and less sustainable, but potentially difficult to refuse.)
Almost certainly, the developer will have a planning condition that no surface water from the development shall pass to the public sewer and will therefore have to look to a free-standing solution for dealing with surface water. Probably the Lead Local Flood Authority will also have advised that run-off from the site should not exceed greenfield conditions. Maybe this will lead to a SuDS scheme for the development where good design could yield substantial savings on development costs over pipes and underground storage.
However, the developer will still be faced with the obstacle of not being able to discharge foul drainage from the development to the local sewer because of lack of capacity.
This is where SuDS can really come to the aid of the developer and enable development to proceed. ‘Back of an envelope calculations’ show that removing run-off generated from perhaps 100m2 of existing impermeable area from the sewer will yield enough capacity for the foul drainage from 50 new homes. Undertaking some local “retrofitting” of SuDS can therefore enable development that might otherwise be delayed and/or subject to significant infrastructure costs and be less viable.
Whilst some aspects of the above scenario may seem fanciful, it is not wholly fictitious. The experiences will often generate a process where outcomes are uncertain and where it will take several years to get development moving. The local council may lose its affordable housing and may be subject to pressure from developers on other sites outside its Local Plan. The developer may be pressured into paying for classic sewerage improvements. The sewerage undertaker may be pressured into bringing forward investment ahead of its agreed plans.
The solution suggested is not, as they say, ‘rocket science’. It is simply good, common sense engineering: delivering a robust solution as cheaply as possible and responding well to a planning system that will always have ‘grey areas’ to wrestle with. Why would a developer not wish to use SuDS creatively if they are concerned about their bottom line and, being in control of timing and processes around their own development?