The Minimal Impact Design Standards calculator requires a user to input a value for water stored in an underground infiltration practice below the outflow (overflow) pipe and the top of the underlying soil or engineered media. This is not a straightforward calculation because there are a wide variety of underground pipe shapes and because two different calculations must be made - one for storage in the pipe and another for storage in the media surrounding the pipe. If engineered media is used in the practice, the calculator also requires a calculation of the surface area of the engineered media. This calculation is fairly simple. Both these calculations can be made using a spreadsheet developed for this purpose.