Evolving environmental regulations in southern California pose new challenges for managing water quality for municipalities, industry, and the general public. Recent stormwater permits adopted in southern California, as well the upcoming Total Maximum Daily Loads (TMDLs), require the control of runoff from new development and significant redevelopment projects. An example of this are the SUSMPs – or Standard Urban Stormwater Mitigation Plans – which specify on-site runoff controls that may work in some places for certain pollutants, they are not uniformly effective and many are less effective in addressing the toxic pollutants of concern. Conversely, comprehensive regional best-management practices (BMPs) that treat runoff from new development sites and surrounding multi land use areas offer greater receiving water benefits and cost effectiveness. Regional facilities, particularly when designed in tandem or as “treatment trains,” can remove pollutants more reliably while proving recreational, aesthetic, and environmental benefits. Watershed-based solutions, when fully implemented, can substantially reduce pollutant loads in urban runoff more efficiently and at a reasonable cost to residents and businesses of the region. The SUSMPs approach typically includes on-site facilities such as water quality inlet filter devices, oil/water separators, or localized hydrodynamic separators. Proprietary devices that are often employed as SUSMP remedies have limited track records on long-term effectiveness in removing pollutants. Significantly, SUSMPs are required for most projects regardless of the project’s location or potential for pollution. Even though the regulatory authorities appear to recognize the merits of watershed-based regional solutions, they require the approval of the Regional Water Quality Control Board (RWQCB) Executive Officer attesting that the proposal is technically valid and appropriate. As a result, the regulated community is challenged with accepting to construct on-site controls that may not work well and are not cost-effective to implement or embarking on a seemingly enduring and expensive debate with the regulatory community. When implemented at full scale, regional solutions will require funding for facility construction and annual operation and maintenance. Stormwater program costs, including mitigating new development impacts, may be funded under a variety of mechanisms. Unlike private organizations or developers, only governmental entities have the authority to raise public funds for construction, operation and maintenance of regional stormwater facilities. Ultimately, the solution lies in developing a partnership between municipal entities and the development community that is grounded in a dedicated, sustainable funding source, such as through regional ballot measures. Regional systems for managing stormwater are currently in use elsewhere in the country and are gathering momentum in California. In response to permit conditions requiring on-site controls for new developments, there have been several proposals for regional approaches. 1 Managing Scientist, Brown and Caldwell – San Diego 2 Water Resources Practice Leader, Brown and Caldwell – Walnut Creek 3 Manager of Financial Services, Brown and Caldwell – Irvine 4 Managing Scientist, Brown and Caldwell – San Diego 876 Regional Solutions to Runoff Pollution