42-239.6 Standards for Stormwater Control Measures

  1. Evaluation According to Contents of Stormwater BMP Manual. All stormwater control measures and structural stormwater BMPs required under this Subpart B shall be evaluated by the Water Quality Administrator according to the policies, criteria, and information, including technical specifications and standards and the specific design criteria for each stormwater practice, in the Stormwater BMP Manual. The Water Quality Administrator shall determine whether proposed stormwater BMPs will be adequate to meet Subpart B requirements.
  2. Determination of Adequacy; Presumptions and Alternatives. Stormwater treatment practices that are designed, constructed, and maintained in accordance with the criteria and specifications in the Stormwater BMP Manual will be presumed to meet the minimum water quality and quantity performance standards of Subpart B. Whenever an applicant proposes to utilize a practice or practices not designed and constructed in accordance with the criteria and specifications in the Stormwater BMP Manual, the applicant shall have the burden of demonstrating that the practice(s) will satisfy the minimum water quality and quantity performance standards of Subpart B. The Water Quality Administrator may require the applicant to provide the documentation, calculations, and examples necessary so he/she may determine whether such an affirmative showing is made.
  3. Separation from Seasonal High Water Table. For stormwater BMPs that require a separation from the seasonal high water table, the separation shall be provided by at least 12 inches of naturally occurring soil above the seasonal high water table.