Stormwater runoff is a leading cause of the severe degradation of Washington DC’s water bodies. Prior to 2013, the standards in terms of run-off regulation were too low. As such, the Washington DC District Department of the Environment (DDOE) introduced new standards by which to determine whether an area needed to be retrofit with runoff-reducing green infrastructure. The question of who should pay for the necessary retrofits was controversial, however. The DDOE has an annual budget of USD $17 million for stormwater policies, whereas the total cost for retrofitting all areas affected by the new standards could cost up to USD $7 billion. The DDOE therefore created the Stormwater Retention Credit trading program (SRC) to lower compliance costs of regulated sites while maximizing benefits for District water bodies.
The SRC program creates a market for voluntary stormwater retrofits in Washington DC. The program also allows regulated sites to meet their obligations by buying SRCs from unregulated properties elsewhere in the city. Other District properties generate SRCs by exceeding their own regulatory requirements or voluntarily installing retention infrastructure such as green roofs and rain gardens. The SRC market provides flexible and cost-effective compliance options for the regulated community as well as financial incentives to voluntarily increase stormwater retention in the District.
The SRC is expected to achieve an overall better score in terms of required retention volumes throughout the district. Additionally, because the SRC allows areas to comply with the new regulations by supporting the installation of green infrastructure off-site, it should result in a greater number of small green infrastructure units that are more able to drain “first flush” stormwaters, which are the most polluting. Moreover, the off-site provisions in the regulations have the potential to result in a large amount of green infrastructure being installed in less affluent parts of the city.
Though it is too soon to make a direct quantitative assessment, the DDOE has methodology in place to measure and report on the program’s environmental and financial impact. The DDOE will also compare the outcomes under the trading program to what the outcomes would have been if regulated sites had been required to achieve all of their required retention volume on site.