Santa Barbara County Bioretention Sizing Calculator

Santa Barbara County and other communities overseen by the Central Coast Regional Water Quality Control Board (Region 3) are required to provide treatment and onsite retention for the 95th percentile, 24-hour storm for development projects surpassing specific thresholds. For most communities, this means fully capturing and infiltrating storms up to 2 inches in depth. Dubin Environmental prepared a SBUH calculator that allows users to iteratively plan out drainage basins and size Stormwater Control Measures (SCMs – bioretention basins). The Excel-based software makes extensive use of VBA coding to maintain a clean user interface while generating complex hydraulic calculations in the background. The SCM Sizing Calculator surpassed the expectations of Santa Barbara staff and is being adopted by other communities within Region 3. Follow-on modeling assignments have been performed for regulatory submittals. Examples include a detailed demonstration of how self-retaining areas can control upstream stormwater runoff and how bioretention basins sized to meet the onsite retention requirement can also mitigate site runoff during very large storms.

Services: Modeling, LID/GSI