West Virginia Code of State Rules › Agency 47 - Water Resources, Division Of Water And Waste Management › Title 47 - LEGISLATIVE RULE DEPARTMENT OF ENVIRONMENTAL PROTECTION DIVISION OF WATER RESOURCES › Series 47-02 - Requirements Governing Water Quality Standards › Section 47-2-5 - 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 secretary 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 secretary 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 are not limited to, the linear distances from the point of
				discharge, surface area involvement, and 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 secretary 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 secretary. 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 secretary, 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 secretary 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
				secretary 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 five (5) cubic feet per second (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; kill 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 percent (10%) 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.
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 State or Federal 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
				the instream waste concentration of a discharge is greater than 80%.
5.2.h.5. Overlap one another, except that the
				secretary may allow mixing zones for human health criteria to overlap, if the
				overlapping mixing zones comply with all guidelines and conditions of
				subsection 5.2 herein.
5.2.h.6.
				Overlap any half-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
				Federal Act shall constitute compliance with all provisions of this
				section.
5.2.j. The secretary may
				waive the requirements of subdivision 5.2.e and paragraph 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 subdivisions 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 secretary that the
				mixing zone is in compliance with the provisions outlined in subdivisions
				5.2.b, 5.2.c, 5.2.e, and paragraph 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 secretary may
				require a permit applicant or permittee to submit such information as he or she
				deems necessary.