The MS4 Permit requires Ann Arbor Public Schools ensure the stormwater runoff flow rates and volume (if feasible) do not increase for the 1-inch storm, the 2-year storm 24-hr (2.35 inches) or the 100-year 24-hr storm (5.11 inches). Permits also require Ann Arbor Public Schools to treat stormwater to remove solids, floaters, and 80% of total suspended solids. Though this project increases the impervious surface, water is stored in underground tanks and surface basins while throttling the outflow rate to lower than existing conditions, and infiltrating groundwater into the soils to ensure surface runoff does not increase. All surface runoff is directed away from neighboring properties and into the storm sewers and pond that it currently flows to. All underground stormwater infiltration will be at a level 7’-8’ below adjacent property basements and will not worsen basement flooding.