Dear All,

This credit requires that project retains on site (i.e. infiltrate, evapotranspirate, or collect and reuse) the runoff from the developed site for, at minimum, the 80th percentile of regional or local rainfall events using low-impact development (LID) /green infrastructure (GI) practices.

Two questions:

  1. a landscaped area (e.g., garden) is considered developed site? Or can it be excluded from credit calculations?

  1. is it necessary to intercept and retain rainwater runoff from all impervious surfaces (developed site) ? Or is it allowable to let some runoff to flow out of the site as long as the capacity to retain the required volume (calculated using the 80th percentile of regional or local rainfall) for the site as a whole is installed (i.e., tradeoffs between impervious surfaces, installing larger retention capacity in some of them to compensate for others where smaller capacity is installed) ?

Thanks in advance.