455B.195  Use or analysis of credible data.
  1.  For any use or analysis of credible data described in section 455B.194, subsection 1, all of the following shall apply:
  a.  The use of credible data shall be consistent with the requirements of the federal Water Pollution Control Act, 33 U.S.C. §  1251 et seq.
  b.  The data quality for removal of water of the state from any list of impaired waters including any section 303(d) list shall be the same as the data quality for adding a water to that list.
  c.  A water of the state shall not be placed on any section 303(d) list if the impairment is caused solely by violations of national pollutant discharge elimination system program permits or storm water permits issued pursuant to section 455B.103A and the enforcement of the pollution control measures is required.
  d.  A water of the state shall not be placed on any section 303(d) list if the data shows an impairment, but existing technology-based effluent limits or other required pollution control measures are adequate to achieve applicable water quality standards.
  e.  If a pollutant causing an impairment is unknown, the water of the state may be placed on a section 303(d) list. However, the department shall continue to monitor the water of the state to determine the cause of impairment before a total maximum daily load is established for the water of the state and a water of the state listed with an unknown status shall retain a low priority for a total maximum daily load development until the cause of the impairment is determined unless the department, after taking into consideration the use of the water of the state and the severity of the pollutant, identifies compelling reasons as to why the water of the state should not have a low priority.
  f.  When evaluating the waters of the state, the department shall develop and maintain three separate listings including a section 303(d) list, a section 305(b) report, and a listing for which further investigative monitoring is necessary. The section 305(b) report shall be a summary of all potential impairments for which credible data is not required. If credible data is not required for a section 305(b) report, the placement of a water of the state on any section 305(b) report alone is not sufficient evidence for the water of the state’s placement on any section 303(d) list. When developing a section 303(d) list, the department is not required to use all data, but the department shall assemble and evaluate all existing and readily available water quality-related data and information. The department shall provide documentation to the regional administrator of the federal environmental protection agency to support the state’s determination to list or not to list its waters.
  g.  The department shall take into consideration any naturally occurring condition when placing or removing any water of the state on any section 303(d) list, and establishing or allocating responsibility for a total maximum daily load.
  h.  Numerical standards shall have a preference over narrative standards. A narrative standard shall not constitute the basis for determining an impairment unless the department identifies specific factors as to why a numeric standard is not sufficient to assure adequate water quality.
  i.  If the department has obtained credible data for a water of the state, the department may also use historical data for that particular water of the state for the purpose of determining whether any trends exist for that water of the state.
  2.  This section shall not be construed to require or authorize the department to perform any act listed in section 455B.194, subsection 1, not otherwise required or authorized by applicable law.
2000 Acts, ch 1068, §12