West Virginia Code of State Rules › Agency 46 - Coal Mine Health And Safety › Title 46 - PROCEDURAL RULE ENVIRONMENTAL QUALITY BOARD › Series 46-01 - Requirements Governing Water Quality Standards › Section 46-1-5 - Mixing Zones

Current through Register Vol. XLI, No. 28, July 12, 2024
5.1. In the permit review and planning
				process or upon the request of a permit applicant or permittee, the Chief may
				establish on a case-by-case basis an appropriate mixing zone.
5.2. The following guidelines and conditions
				are applicable to all mixing zones:
5.2.a.
				The Chief will assign, on a case-by-case basis, definable geometric limits for
				mixing zones for a discharge or a pollutant or pollutants within a discharge.
				Applicable limits shall include, but may not be limited to, the linear
				distances from the point of discharge, surface area involvement, volume of
				receiving water, and shall take into account other nearby mixing zones. Mixing
				zones shall take into account the mixing conditions in the receiving stream
				(i.e: whether complete or incomplete mixing conditions exist). Mixing zones
				will not be allowed until applicable limits are assigned by the Chief in
				accordance with this section.
5.2.b. Concentrations of pollutants which
				exceed the acute criteria for protection of aquatic life set forth in Appendix
				E, Table 1 shall not exist at any point within an assigned mixing zone or in
				the discharge itself unless a zone of initial dilution is assigned. A zone of
				initial dilution may be assigned on a case-by-case basis at the discretion of
				the Chief. The zone of initial dilution is the area within the mixing zone
				where initial dilution of the effluent with the receiving water occurs, and
				where the concentration of the effluent will be its greatest in the water
				column. Where a zone of initial dilution is assigned by the Chief, the size of
				the zone shall be determined using one of the four alternatives outlined in
				section 4.3.3 of US EPA's Technical Support Document for Water Quality-based
				Toxics Control (EPA/505/2-90-001 PB91-127415, March 1991). Concentrations of
				pollutants shall not exceed the acute criteria at the edge of the assigned zone
				of initial dilution. Chronic criteria for the protection of aquatic life may be
				exceeded within the mixing zone but shall be met at the edge of the assigned
				mixing zone.
5.2.c. Concentrations
				of pollutants which exceed the criteria for the protection of human health set
				forth in Appendix E, Table 1 shall not be allowed at any point unless a mixing
				zone has been assigned by the Chief after consultation with the Commissioner of
				the West Virginia Bureau for Public Health. Human health criteria may be
				exceeded within an assigned mixing zone, but shall be met at the edge of the
				assigned mixing zone. Mixing zones for human health criteria shall be sized to
				prevent significant human health risks and shall be developed using reasonable
				assumptions about exposure pathways. In assessing the potential human health
				risks of establishing a mixing zone upstream from a drinking water intake, the
				Chief shall consider the cumulative effects of multiple discharges and mixing
				zones on the drinking water intake. No mixing zone for human health criteria
				shall be established on a stream which has a seven (7) day, ten (10) year
				return frequency of 5 cfs or less.
5.2.d. Mixing zones, including zones of
				initial dilution, shall not interfere with fish spawning or nursery areas or
				fish migration routes; shall not overlap public water supply intakes or bathing
				areas; cause lethality to or preclude the free passage of fish or other aquatic
				life; nor harm any threatened or endangered species, as listed in the Federal
				Endangered Species Act, 15
				U.S.C. §1531 et seq.
5.2.e. The mixing zone shall not exceed
				one-third (1/3) of the width of the receiving stream, and in no case shall the
				mixing zone exceed one-half (1/2) of the cross-sectional area of the receiving
				stream.
5.2.f. In lakes and other
				surface impoundments, the volume of a mixing zone shall not affect in excess of
				ten (10) percent of the volume of that portion of the receiving waters
				available for mixing.
5.2.g. A
				mixing zone shall be limited to an area or volume which will not adversely
				alter the existing or designated uses of the receiving water, nor be so large
				as to adversely affect the integrity of the water body.
5.2.h. Mixing zones shall not:
5.2.h.1. Be used for, or considered as, a
				substitute for technology-based requirements of the Act and other applicable
				state and federal laws.
5.2.h.2.
				Extend downstream at any time a distance more than five times the width of the
				receiving watercourse at the point of discharge.
5.2.h.3. Cause or contribute to any of the
				conditions prohibited in section 3, herein.
5.2.h.4. Be granted where instream waste
				concentration of a discharge is greater than 80%.
5.2.h.5. Overlap one another.
5.2.h.6. Overlap any 1/2 mile zone described
				in section 7.2.a.2 herein.
5.2.i. In the case of thermal discharges, a
				successful demonstration conducted under section 316(a) of the Act shall
				constitute compliance with all provisions of this section.
5.2.j. The Chief may waive the requirements
				of subsections 5.2.e and 5.2.h.2 above if a discharger provides an acceptable
				demonstration of:
5.2.j.1. Information
				defining the actual boundaries of the mixing zone in question; and
5.2.j.2. Information and data proving no
				violation of subsections 5.2.d and 5.2.g above by the mixing zone in
				question.
5.2.k. Upon
				implementation of a mixing zone in a permit, the permittee shall provide
				documentation that demonstrates to the satisfaction of the Chief that the
				mixing zone is in compliance with the provisions outlined in subsections 5.2.b,
				5.2.c, 5.2.e, and 5.2.h.2, herein.
5.2.l. In order to facilitate a determination
				or assessment of a mixing zone pursuant to this section, the Chief may require
				a permit applicant or permittee to submit such information as deemed
				necessary.