A majority of storm water from impervious surface is managed. This indicator measures the percent of impervious area managed by two types of storm water permits. Storm water is precipitation that runs off impervious surfaces rather than infiltrating into the soil. Operational storm water permits address storm water from projects over 1 acre of disturbance. The MS4 permit covers permitting in nine municipalities and three public entities in Chittenden County: Burlington, Colchester, Essex, Essex Junction, Milton, Shelburne, South Burlington, Williston, Winooski, Burlington International Airport, UVM and VTrans.