We are modeling several BMPs with ICM 7.5 but are unsure of how to handle the BMP footprint within the catchment. See questions below:

1/Do we need to subtract the BMP footprint area from the catchment tributary area?
2/If the BMP is built on an area that’s impervious within the catchment, do we need to recalculate the percent impervious and percent pervious in the catchment once the BMP footprint is subtracted from the catchment tributary area?
3/If the BMP is built on an area that’s pervious within the catchment, do we need to recalculate the percent impervious and percent pervious in the catchment once the BMP footprint is subtracted from the catchment tributary area?
4/ Do the responses to the questions above apply to all types BMPs equally (green roofs, infiltration trenches, porous pavement, bio-retention…)?

Thanks,