Scottish Awards for Quality in Planning 2000
Commendation for development on the ground
28: SUSTAINABLE URBAN DRAINAGE SYSTEM IN EAST DUNFERMLINE EXPANSION AREA
nominated in 2000 by the Planning and Building Control Service, Fife Council.
The Dunfermline East Expansion Area (DEX) was identified in the 1994 Fife Structure Plan as the area best located to accommodate the town's expansion needs over the next 20 years. The site extends to approximately 290 hectares, with an additional 30 hectares of brown field land on former MOD property south west of the main DEX area. Having identified this site for development, the former Fife Regional and Dunfermline District Councils along with Fife Enterprise commissioned consultants to produce a master plan for the area. Prior to the completion of this master plan, 2 outline planning applications were submitted by separate developers for the 2 areas which make up the DEX site. The DEX area drained naturally to 4 water courses which flow to the south and west of the site. All of these pass through developed areas downstream of the DEX site, and all are subject to flooding. The development of the DEX site using conventional drainage methods would have exacerbated the flooding position downstream on these water courses. An alternative method of drainage therefore had to be devised to allow the development of the identified major expansion area whilst preventing problems downstream.
In the mid 1990s the Forth River Board, and then the Scottish Environment Protection Agency (SEPA), had been promoting the concept of what was then known as Best Management Practice in the disposal of surface water. The basic concept behind this approach to surface water is to, where possible, deal with it at source, slow down the forward flow of storm water which results from the installation of a conventional piped system and do so in a way which is practical and sustainable. The outline planning consents granted for the DEX area contained a condition that best management practice be used in dealing with the surface water from the site. The method possible to achieve this was limited by the clay which covers most of the DEX area and which precludes infiltration as a disposal method.
Fife Council working with SEPA employed specialist consultants who ran a series of workshops for all of those involved in the DEX area with a view to explaining the concepts of Best Management Practice, disseminating best practice and dealing with practical problems. As a consequence of the conditions of the outline planning consents and the information conveyed through the workshops, a general approach was agreed on the way that Best Management Practice could be employed in East Dunfermline. The basic parameters for this were set out in a "completion report" produced by consultants acting on behalf of the Council. Perhaps the most significant design constraint coming from this is that which requires the surface water run off from the developed site to be no greater than that of the site prior to development. This has been achieved by dividing the site on to its natural catchment areas. Within these areas assumptions have been made as to the likely level of development. This information, allied to that relating to local rainfall data, is combined to calculate the size of ponds that will be required to cope with the 1 in 100 year storm, whilst ensuring compliance with the terms of the completion report.
The result on the ground is a series of ponds which act to attenuate the forward flow of surface water and, significantly, also help to improve the quality of surface water prior to discharge to the water courses. The quality issue is achieved by the design of the ponds causing suspended solids to be removed and the water being retained within the ponds for a period of 14-21 days during which time the biological reaction between the aquatic planting and the "polluted" water results in an improvement in water quality. The ponds as now constructed are a significant amenity feature within East Dunfermline expansion area and their ecological benefits are becoming more apparent as the vegetation becomes established., However, the planning applications submitted for the ponds were the subject of significant controversy, particularly with regards to the safety aspects of having such large bodies of water close to housing. To overcome this problem, and provide the reassurance necessary, the Planning Service devised a four point plan to optimise the safety of the ponds. The 4 aspects regarded as important for the safety of the ponds are:
1) Pond design - The ponds themselves are designed with a shallow slide slope (maximum 1 in 4) both above and below the water level for a distance of at least 5 metres into the pond.
2) Barrier planting - Around the edge of all ponds is a belt of phragmites which extends into the pond for a depth of 4 to 6 metres minimum. This tall reed, whilst being critical to the performance of the pond in terms of improving water quality, is also effective in deterring entry to the water. Above the water line is inhospitable shrub planting on the pond side slopes which is specifically designed to deter access through it.
3) Fencing - Beyond the barrier planting is a 1 metre high metal fence designed as a deterrent to younger children who may be living close to the ponds. The design of the fence is such that it will only be effective in keeping out the very youngest of children, but equally it will not be a deterrent to adults, should access be required in the case of emergency.
4) Pond location - All of the ponds are located in such a way that there is a degree of natural surveillance provided by those using the peripheral land. This is achieved either through the provision of roads and footpaths or housing directly adjacent to, and overlooking the ponds.
The Dunfermline East expansion area represents the first time that the sustainable urban drainage system approach has been applied to such a large area in a comprehensive way. Fife Council Planning Service have had a major input to both the approach generally, the detailed design of the individual ponds and resolving the problems identified, particularly by Councillors with regard to safety.
The problems which had to be tackled in dealing with the applications within the Dunfermline expansion area pre-date the publication of the design manual for sustainable urban drainage systems published by CIRIA. As part of the wider East Dunfermline expansion, a Liaison Committee has been operating for the past two years at which all those involved in the development of the area and those representing the communities bordering the area are involved. Information on the urban drainage system has been given to the Liaison Committee and presentations made to a number of public meetings. Fife Council Education Service have also been involved as part of the safety strategy and are currently giving consideration to the positive use of the ponds within the school curriculum. The application of sustainable urban drainage system principles within East Dunfermline has demonstrated in a very practical way the benefits of this approach to surface water management. Whilst the attenuation/treatment ponds are only one method by which substantial urban drainage systems can be employed, the East Dunfermline experience illustrates they are particularly effective and have benefits which extend way beyond their drainage function.
The judges visited the Dunfermline Eastern Expansion Area, to see the implementation of sustainable urban drainage on the ground. As always, there is a gap between good ideas being recognised and their consistent application and public acceptance across the country. The judges are delighted to see that the principle of sustainable urban drainage has been realised in practice in this major urban expansion. Both in terms of engineering and public safety, the design has been well executed. But the judges would like these principles applied to future developments in a way which achieves greater integration with wider landscape and nature conservation objectives. They recall that Fife's work on biodiversity was recognised in 1998. Beyond the scope of this nomination, the judges note that many major urban expansions of the kind being carried out at East Dunfermline lack identity. They want to see good examples across Scotland, and challenge planners and housebuilders to work together to supply them. These are considerations for future years. For the present, the judges congratulate the Fife Planning Service for taking the first step. They recommend the Sustainable Urban Drainage System at East Dunfermline for commendation in this category.