Benefit Cost Analysis of Regional Urban Stormwater Retention in Orange County, California
Within the past five years, municipal separate storm sewer system (MS$) permits in California have begun to allow alternative means of compliance for meeting post construction on-site runoff retention control requirements when it is shown to be as or more effective than on-site retention.
The County of Orant wants to understand the feasibility of implementing a stormwater retention alternative compliance program which would result in compliance with their MS4 permits and provide flexibility for new and re-development. Two proof-of=concept urban stormwater runoff retention projects were evaluated: Legacy Campus Plan Project and the Fletcher Basin flood control retardation basin retro fit project.
The two projects are case studies comparing use of regional water quality credit generating facility versus use of distributed surfaces retention best practices for urban runoff management at land development projects. The case studies illustrate how different approaches in managing urban runoff result in benefits to the community and how fast or slow benefits are realized.
A key question examined is what is the potential value to the community of creating a water quality credit generating facility in lieu of distributed, future retention practices installed at new and re-development projects within a watershed as development proceeds over time?
