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Defined as “the area in which the public water supply utility would have little or no time to respond to a direct discharge of contamination, other than to close the intake.” The area closest to the intake was designed to help the public water supplier address contaminant releases which present an immediate (acute) health concern to water users. The geographic area is defined by the amount of notification time the PWS would need to close the surface intake and a "buffer time" to accommodate unanticipated delays in notification and shut down. Three different sets of criteria were developed and used to delineate an ERA for different types of surface water bodies including: 1) rivers and streams, 2) lakes, and 3) mine pits. Information about the intake, water supply system, water storage capacity, treatment methods was also considered. |