"Background pollutant concentration" means the . water body concentration immediately upstream/upcurrent of a permitted discharge, regardless of whether those pollutants are natural or result from anthropogenic upstream activity.
"Intake pollutant" means the background pollutant concentration that is present in the intake water body, which must be the same water body as the receiving water for the discharge at the time it is withdrawn from such waters.
"Same body of water" means an intake pollutant is considered to be from the 'same body of water" as the discharge if the department finds that the intake pollutant would have reached the vicinity of the outfall point in the receiving water within a reasonable period of time had it not been removed by the permittee. This finding may be deemed established if:
The department may consider other site-specific factors relevant to the transport and fate of the pollutant in deciding whether a pollutant would or would not have reached the vicinity of the outfall point in the receiving water within a reasonable period had it not been removed by the permittee.
Haw. Code R. § 11-54-12