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California Phase II LID Sizing Tool - v1.2

Welcome to the California Phase II Low Impact Development (LID) Sizing Tool. This is a web-based tool that assists stormwater practitioners in selecting and sizing LID Best Management Practices (BMPs) that meet the sizing requirements set forth in California’s National Pollutant Discharge Elimination System (NPDES) permit for stormwater discharges from small municipal separate storm sewer systems (MS4s).

Development of this tool was funded by the California State Water Resources Control Board’s (SWRCB) Proposition 84 Stormwater Grant Program (SWGP) and the California Department of Parks and Recreation

Changes from v1.1 to v1.2

The continuous simulation results for porous pavement were improved. SWMM 5.0 had an error where water would not infiltrate correctly in porous pavements. SWMM 5.1 has fixed this error and was used for porous pavement calculations. In some cases, the required porous pavement LID BMP footprint area is now use much less. The other LID BMP calculations and results have not changed.

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