Stormwater. The neighbors are interested to know what will happen to flooding on their properties when the entirely previous site is more than 60% of the site is lost to tree root storage and the impact of impervious surfaces.
The developer is proposing two water supply storage systems which will reduce the rate and volume of storm water that flows off the site. These facilities are sized for the 25 year storm. The immediate question that comes to mind is will this be adequate for the 500 year storms we are experiencing.
This tract is presently a tree farm and entirely pervious. Rainwater that falls is mostly absorbed into the ground and only an average of 10% runoff is likely to occur. The Aura proposal would cover 66% of the tract with hard and impervious surfaces. Under these conditions,it would be impossible to hold all the rainwater on site, and neighboring properties could receive as much as an average of 55% runoff.
Here are links to documents from the Army Corp of Engineers and Chapel Hill Stormwater.