The credit requires "the percentile rainfall event is the total rainfall on a given day in the record that is greater than or equal to X percent of all rainfall events over a 20-to 40+-year period". Can anybody explain to me what this means?
Thanks
Wayne
Eliot Allen
LEED AP-ND, PrincipalCriterion Planners
LEEDuser Expert
303 thumbs up
June 2, 2011 - 6:22 pm
A detailed description of the requirement appears in the ND Reference Guide. In practioce, the requirement allows a project team to select the amount of rainfall that will be managed on-site and not discharged to a community stormwater system. If a project desires to manage the maximum amount of stormwater, it would select the 95th percentile event. This mean the quantity of rainfall to be managed is the 24-hour rainfall amount equal or greater than 95% of all rainfall events over the past 20-40 years. The number of years used should correspond to the length of local rainfall records.