312 IAC 25-6-79 Underground mining; hydrologic balance; diversions of perennial streams, intermittent streams with a watershed greater than one square mile, miscellaneous flows; stream channel diversions; supplemental requirements

Sec. 79. (a) This section provides requirements that are supplemental to those contained in section 78 of this rule for: (1) diversions of perennial streams; (2) intermittent streams with a watershed greater than one (1) square mile; and (3) miscellaneous flows. Subsection (b) governs perennial streams and intermittent streams with a watershed greater than one (1) square mile. Subsection (c) governs miscellaneous flows. (b) Requirements for temporary and permanent diversions are as follows: (1) Diversion of perennial streams and intermittent streams with a watershed greater than one (1) square mile may be approved by the director after making a finding related to stream buffer zones that the diversions will not adversely affect the water quantity and quality and related environmental resources of the stream. (2) The design capacity of channels for temporary and permanent stream channel diversions shall be at least equal to the capacity of the unmodified stream channel immediately upstream and downstream from the diversion. (3) The requirements of section 78(d)(2) of this rule shall be met when the temporary and permanent diversions for intermittent streams having a watershed greater than one (1) square mile and perennial streams are designed so that the combination of channel, bank, and floodplain configuration is adequate to pass safely the peak run-off of a ten (10) year, six (6) hour precipitation event for a temporary diversion and a one hundred (100) year, six (6) hour precipitation event for a permanent diversion. (4) All stream channel diversions subject to this subsection shall be designed under the supervision of a qualified registered professional engineer in accordance with good engineering practices and the requirements of this section and shall be certified after construction by the qualified registered professional engineer as having been constructed in accordance with the approved plans. (c) Requirements for miscellaneous flows are as follows: (1) Miscellaneous flows, which consist of all flows except those specified in subsection (b), may be diverted around disturbed areas if required and approved by the director. Miscellaneous flows include ground water discharges, overland flow, ephemeral streams, and intermittent streams having a watershed not greater than one (1) square mile. (2) The design, location, construction, maintenance, and removal of diversion of miscellaneous flows shall meet all the performance standards set forth in section 78 of this rule. (3) The requirements of section 78(d)(2) of this rule shall be met when the temporary and permanent diversions for miscellaneous flows are designed so that a combination of channel, bank, and floodplain configuration is adequate to pass safely the peak run-off of a two (2) year, six (6) hour precipitation event for a temporary diversion and a ten (10) year, six (6) hour precipitation event for a permanent diversion.