(1) General provisions. The following provisions apply to the consideration of intake credits in determining reasonable potential and establishing water quality based effluent limits (WQBELs).

(a) An "intake pollutant" is the amount of a pollutant that is present in waters of the state (including groundwater except as provided in (c) of this subsection) at the time water is removed from the same body of water by the discharger or other facility supplying the discharger with intake water.

(b) An intake pollutant must be from the "same body of water" as the discharge in order to be eligible for an intake credit. 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 had it not been removed by the permittee. This finding will be established if a discharger demonstrates:

(i) The background concentration of the pollutant in the receiving water (excluding any amount of the pollutant in the facility's discharge) is similar to that in the intake water; and

(ii) There is a direct hydrological connection between the intake and discharge points.

(c) An intake pollutant in groundwater partially or entirely due to human activity is not eligible for use of an intake credit.

(d) Where intake water for a facility is provided by a municipal water supply system and the supplier provides treatment of the raw water that removes an intake water pollutant, the concentration of the intake water pollutant will be determined at the point where the water enters the water supplier's distribution system.

(e) Where a facility discharges intake pollutants from multiple sources that originate from the receiving water body and from other water bodies, the department may derive an effluent limit reflecting the flow-weighted amount of each source of the pollutant provided that conditions in subsection (3) of this section are met and adequate monitoring to determine compliance can be established and is included in the permit.

(f) The department may also consider other site-specific factors relevant to the transport and fate of the pollutant to make the finding in a particular case that 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.

(2) Consideration of intake pollutants in reasonable potential determination.

(a) The department may determine there is no reasonable potential for the discharge of an identified intake pollutant to cause or contribute to an exceedance of a narrative or numeric water quality criterion where a discharger demonstrates that all the following conditions are met:

(i) The facility removes the intake water containing the pollutant from the same body of water into which the discharge is made;

(ii) The facility does not alter the identified intake pollutant chemically or physically in a manner that would cause adverse water quality impacts to occur that would not occur if the pollutant had not been removed from the body of water;

(iii) The timing and location of the discharge would not cause adverse water quality impacts to occur that would not occur if the identified intake pollutant had not been removed from the body of water;

(iv) The facility does not increase the identified intake pollutant concentration at the edge of the mixing zone, or at the point of discharge if a mixing zone is not allowed, as compared to the pollutant concentration in the intake water, unless the increased concentration does not cause or contribute to an excursion above an applicable water quality standard; and

(v) The facility does not contribute any additional mass of the identified intake pollutant to its wastewater.

(b) Upon a finding under (a) of this subsection that an intake pollutant in the discharge does not cause, have the reasonable potential to cause, or contribute to an exceedance of an applicable water quality standard, the department is not required to include a water quality-based effluent limit for the identified intake pollutant in the facility's permit.

(3) Consideration of intake pollutants in establishing water quality based effluent limits.

(a) This subsection applies only when the ambient background concentration of the intake pollutant does not meet the most stringent applicable water quality criterion for that pollutant;

(b) The requirements of subsection (2)(a)(i) and (iv) also apply to this subsection.

(c) A discharger may add mass of the pollutant to its waste stream if an equal or greater mass is removed prior to discharge, so there is no net addition of the pollutant in the discharge compared to the intake water.

(d) Where the conditions of this subsection are met, the department may establish effluent limits using an intake credit. The facility's permit must specify how compliance with the limits will be assessed.