1. (a) Hydrologic analysis shall be performed to demonstrate that the requirements of Env-Wq 1507.05 and Env-Wq 1507.06 are met, unless all of the following criteria are met:

   1. (1) Land slopes are 5% or less;
   2. (2) Conditions for sheet flow, as described by Env-Wq 1511.04, will exist for the full solar array;
   3. (3) The existing ground cover is open space, pasture, grassland, or range, as described by NRCS; and
   4. (4) Gravel or paved access roads and other impervious areas, other than solar panels, account for less than 2% of the area of disturbance.

2. (b) Subject to (a), above, for projects that require the submission of a hydrologic analysis, the curve number for the area covered by the solar panels shall be assigned as follows:

   1. (1) If conditions of sheet flow exist for the solar panel, pursuant to Env-Wq 1511.04, the curve number for the area covered by the solar panel shall be based on the following land cover:

      1. a. For land slopes less than or equal to 5%, the land cover shall be considered pervious and assigned the curve number of the land cover beneath the solar panels, as defined by NRCS “National Engineering Handbook”, Part 630, Hydrology, March 2020, or Win TR-20, version 3.20.0000, all available as noted in Appendix B; and
      2. b. For land slopes greater than 5%, the land cover shall be considered unconnected, as defined by equation 9-2 in the NRCS “National Engineering Handbook”, Part 630, Hydrology, March 2020, or Win TR-20, version 3.20.0000, all available as noted in Appendix B.

   2. (2) If conditions of sheet flow do not exist for the solar panel, pursuant to Env-Wq 1511.04, the curve number for the area covered by the solar panel shall be based on the following land cover:

      1. a. For land slopes less than or equal to 5%, the land cover shall be considered unconnected, as defined by equation 9-2 in the NRCS “National Engineering Handbook”, Part 630, Hydrology, March 2020, or Win TR-20, version 3.20.0000, all available as noted in Appendix B; and
      2. b. For land slopes greater than 5%, the land cover shall be considered connected and assigned a curve number of 98.

3. (c) For projects that require the submission of a hydrologic analysis, a curve number soil group plan shall be drawn at a scale of one inch equals 50 feet, or at a scale that provides greater detail, and shall depict the following:

   1. (1) Proposed final contours at 2-foot intervals or less;
   2. (2) The assigned land cover in accordance with (b), above, using distinct symbology for each of the 3 land cover types present: pervious, unconnected, and connected; and
   3. (3) A map legend.

Source. #13758, eff 9-28-23; ss by #14472, eff 1-19-26, EXPIRES: 1-19-36 (formerly Env-Wq 1511.06)