(b)

1. (1) You must fill, regrade, or otherwise stabilize rills and gullies that form in areas that have been regraded and upon which soil or soil substitute materials have been redistributed. This requirement applies only to rills and gullies that -

   1. (i) Disrupt the approved postmining land use or reestablishment of the vegetative cover;
   2. (ii) Cause or contribute to a violation of applicable state or tribal water quality standards or effluent limitations, including, but not limited to, water quality standards established under the authority of section 303(c) of the Clean Water Act, 33 U.S.C. 1313(c), and effluent limitations established in any National Pollutant Discharge Elimination System permit issued for the operation under section 402 of the Clean Water Act, 33 U.S.C. 1342, or its state or tribal counterpart;
   3. (iii) Cause or contribute to a violation of applicable state or tribal water quality standards for groundwater; or
   4. (iv) Result in material damage to the hydrologic balance outside the permit area.
2. (2) You must reapply soil materials to the filled or regraded rills and gullies when necessary to reestablish a vegetative cover. You must then replant those areas.