Section 817.43. Diversions

(a) General requirements.

(1) With the approval of the division, any flow from mined areas abandoned before May 3, 1978, and any flow from undisturbed areas or reclaimed areas, after meeting the criteria of 4VAC25-130-817.46 for siltation structure removal, may be diverted from disturbed areas by means of temporary or permanent diversions. All diversions shall be designed to minimize adverse impacts to the hydrologic balance within the permit and adjacent areas, to prevent material damage outside the permit area and to assure the safety of the public. Diversions shall not be used to divert water into underground mines without approval of the division in accordance with 4VAC25-130-817.41(h).

(2) The diversion and its appurtenant structures shall be designed, located, constructed, and maintained to-

(i) Be stable;

(ii) Provide protection against flooding and resultant damage to life and property;

(iii) Prevent, to the extent possible using the best technology currently available, additional contributions of suspended solids to streamflow outside the permit area; and

(iv) Comply with all applicable local, State, and Federal laws and regulations.

(3) Temporary diversions shall be removed when no longer needed to achieve the purpose for which they were authorized. The land disturbed by the removal process shall be restored in accordance with this Part. Before diversions are removed, downstream water treatment facilities previously protected by the diversion shall be modified or removed, as necessary to prevent overtopping or failure of the facilities. This requirement shall not relieve the permittee from maintaining water treatment facilities as otherwise required. A permanent diversion or a stream channel reclaimed after the removal of a temporary diversion shall be designed and constructed so as to restore or approximate the premining characteristics of the original stream channel including the natural riparian vegetation to promote the recovery and the enhancement of the aquatic habitat.

(4) Diversions which convey water continuously or frequently shall be designed by a qualified registered professional engineer and constructed to ensure stability and compliance with the standards of this Part and any other criteria set by the division.

(5) Channel side slopes shall be no steeper than 1.5h:1v in soil.

(6) Adequate freeboard shall be provided to prevent overtopping. A minimum of 0.3 feet shall be included, with additional freeboard provided at curves, transitions, and other critical sections as required.

(7) When rock rip rap lining is used, consideration shall be given to rip rap size, bedding, and filter material. Rock used for rip rap shall be non-degradable, and non-acid forming such as natural sand and gravel, sandstone or limestone. No clay, shale, or coal shall be used.

(8) Sediment and other debris shall be removed and the diversion maintained to provide the design requirements throughout its operation.

(9) The division may specify other criteria for diversions to meet the requirements of this section.

(b) Diversion of perennial and intermittent streams.

(1) Diversion of perennial and intermittent streams within the permit area may be approved by the division after making the finding relating to stream buffer zones called for in 4VAC25-130-817.57 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 Paragraph (a)(2)(ii) of this section shall be met when the temporary and permanent diversions for perennial and intermittent streams are designed so that the combination of channel, bank and flood-plain configuration is adequate to pass safely the peak runoff of a 10-year, 6-hour precipitation event for a temporary diversion and a 100-year, 6-hour precipitation event for a permanent diversion.

(4) The design and construction of all stream channel diversions of perennial and intermittent streams shall be certified by a qualified registered professional engineer as meeting the standards of this Part and any other criteria set by the division.

(5) Channels which are constructed in backfilled material shall be formed during the backfilling and grading of the area. Unless the backfill material is of sufficiently low permeability, the channel shall be lined to prevent saturation of the backfill, loss of stream flow, or degradation of groundwater quality.

(6) Rock rip rap lining shall be placed in the channels of all diversions of perennial and intermittent streams to the normal flow depth, including adequate freeboard. Channels constructed in competent bedrock need not be rip rap lined.

(c) Diversion of miscellaneous flows.

(1) Miscellaneous flows, which consist of all flows except for perennial and intermittent streams, may be diverted away from disturbed areas if required or approved by the division. Miscellaneous flows shall include ground-water discharges and ephemeral streams.

(2) The design, location, construction, maintenance, and removal of diversions of miscellaneous flows shall meet all of the performance standards set forth in Paragraph (a) of this section.

(3) The requirements of Paragraph (a)(2)(ii) of this section shall be met when the temporary and permanent diversions for miscellaneous flows are designed to pass safely the peak runoff of a 2-year, 6-hour precipitation event for a temporary diversion and a 10-year, 6-hour precipitation event for a permanent diversion.

(d) Steep slope water conveyances.

(1) A steep slope conveyance, including but not limited to a rock rip rap flume, concrete flume, or a pipe, shall be used to convey water down steep slopes to stable natural or constructed drainways. Steep slope conveyances shall be constructed at locations where concentrated flows may cause erosion.

(2) The capacity of the conveyance shall be equal to or greater than the capacity of the inlet ditch or drainage structure associated with it.

Historical Notes

Derived from VR480-03-19 § 817.43, eff. December 15, 1981; amended, eff. June 28, 1982; October 28, 1982; December 14, 1982; October 11, 1983; December 27, 1983; May 8, 1984; June 22, 1984; August 2, 1984; October 16, 1985; January 7, 1987; July 22, 1987; November 25, 1987; October 12, 1988; December 26, 1990; July 1, 1991; July 17, 1991; November 20, 1991; July 7, 1992; May 5, 1993; October 19, 1994; Volume 25, Issue 12, eff. March 18, 2009.

Statutory Authority

§§ 45.1-161.3 and 45.1-230 of the Code of Virginia.