FAQ

Q. This is a lot of information. Where should I begin?  

A. Refer to the helpful guide to approach your challenge. Make sure to include all necessary content for both your project narrative   and visual presentation. Check the Challenge info tab for more details. 

Q. When I look at the calculations on the BMP fact sheet, how do I know what area to measure? 

A. Step 1 equations are used to determine the water quality design volume. Variable A is the BMP drainage area. 

To measure for Variable A for BMPs such as Planter Boxes, Cisterns, or Bioretention/Rain Gardens, you should measure the area of the hard surfaces (like roof tops or parking lots) that will drain to the BMP, rather than the size of the BMP itself.   

For Permeable Pavement, measure the area of the hard surfaces that will drain to the BMP as well as the area replaced with the Permeable Pavement.   

Step 2 of the equations are used to determine the surface area (size) of the actual BMP.   

For Green Roofs see FAQ #3 below. 

Refer to the Mapping, Measuring and Calculating How to Videos under the Resources tab for additional information.  

Q. Where can I find the calculations required for the green roof? 

A. There isn’t a specific equation for the Green Roof; it’s simply measuring the area of conventional roof that is replaced by the Green Roof. Measure the roof you plan to replace using the mapping tool. Be sure to measure in square feet (ft3).