20220804 11083700 1.0 TRUE 2-Apr-26. Zone of Critical Concern (ZCC) – ZCC for a public surface water supply source and for a public surface water influenced groundwater supply source is a corridor along streams within a watershed that warrants detailed scrutiny due to its proximity to the surface water intake and the intake’s susceptibility to potential contaminants within that corridor. The ZCC is determined using a mathematical model that accounts for stream flows, gradient and area topography. The length of the ZCC is based on a five-hour time-of-travel of water in the streams to the water intake.