The objectives of this project are to document the performance and whole-life costs of Best Management Practices (BMPs) and Sustainable Urban Drainage Systems (SUDS). These two terms refer to stormwater practices implemented in the U.S. and UK to reduce the impact of urbanization. The study was undertaken for a number of reasons, including: The lack of data on operational performance (in connection with both water quantity and quality management) A need to better understand future financial liabilities associated with the widespread adoption of these facilities The need to improve confidence in BMPs/SUDS techniques to facilitate appropriate regulation and adoption. The BMPs/SUDS selected for evaluation in this study include retention ponds, extended detention basins, vegetated swales, bioretention, porous pavements, and various infiltration practices. A whole-life cost model was developed in a spreadsheet framework to allow calculation of the expected cost of a facility based on drainage area, maintenance expectations, and other factors. Separate models were developed for five of the selected systems. The default values for many model parameters were extracted from the information gained in the survey of systems in the U.S. and UK.

Over the past 20 years, the use of Best Management Practices (BMPs) in the United States has been instrumental in reducing both the detrimental impacts to receiving water quality and the exacerbated flooding caused by urbanization and storm water drainage. More recently, Sustainable Urban Drainage Systems (SUDS) have started to be used in the United Kingdom. Both SUDS and BMPs attempt to mimic the drainage patterns of the natural watershed, and can also provide a degree of treatment needed to improve the quality of the water discharged to an acceptable level. The costs of conventional stormwater collection systems are determined primarily in terms of initial capital expenditure. Long-term maintenance costs are absorbed by stormwater authorities that are responsible for maintaining their infrastructure as part of their 'asset base'. Currently, only a few of these responsibilities exist for BMPs and SUDS, which generally incorporate surface components and are often dependent on landscaping rather than on traditional construction techniques, but may require significant regular maintenance. Any potential adopting organization will require guidance on the maintenance regimes of different types of systems and how such regimes translate into long-term adoption costs. The project is being conducted in two phases. Phase 1, which is the subject of this report, includes a literature review and a survey of stormwater authorities and organizations in the U.S. and U.K. to identify the most commonly used BMPs and SUDS and to determine the availability of data on their cost and performance. Phase 1 also involves establishment of protocols for whole-life costs and performance data for BMPs and SUDS. Protocols for whole-life costs will be published separately. An additional outcome of Phase 1 will be the selection of a limited number of BMPs and SUDS authorities or sites for qualitative or quantitative monitoring and further assessment during Phase 2.As part of Phase 2, the operation of selected BMPs and SUDS will be monitored over a one-year period in terms of pollutant removal and hydrologic/hydraulic efficiency, and applicability of their design criteria and maintenance regime. The protocols developed in Phase 1 will be used to assess BMPs/SUDS performance and whole-life costs.