Infiltration BMP Tutorial for HSPF

The HSPF BMP tool presented herein is used to design and simulate structural BMPs. Just like storage BMPs, infiltration BMPs use HSPF's reach module (RCHRES). When designing infiltration BMPs, we recommend the use of Maryland's unified stormwater sizing criteria. The unified approach has five spec ific design objectives: meet pollutant removal goals (WQv), maintain groundwater recharge (Rev), reduce channel erosion (CPv), prevent overbank flooding, and pass extreme floods. The HSPF Web-based BMP modeling tool can be as a pretreatment facility or as the main treatment facility. Pretreatment is used mainl y to capture suspended solids before reaching the treatment facility. The pretreatment v olume treats 25% of the water quality volume (WQv) whereas the main treatment facility treats 50% of the water quality volume (WQv). To represent the treatment train in H SPF users should build one FTABLE for the pretreatment and another separate FTABLE for the treatment facility. Tool users must ensure that the two FTABLES are linked through the SCHEMATIC- BLOCK of the User Control Input (UCI) file. Overall, the BMP facility (pretreatment and main treatment) is intended to treat 75% of the wat er quality volume (WQv) generated from the contributing impervious area. Representing most infiltration BMPs in HSPF is stra ightforward. However, to build an FTABLE for some BMPs, i.e. sand filters, may require several steps. Although the tool may be used in many BMP modeling applications, how accurately one can represent a particular BMP depends on a user's skill.