Virginia Law

Chapter 260. Water Quality Standards

Part I
Surface Water Standards with General, Statewide Application

9VAC25-260-5. Definitions.

The following words and terms when used in this chapter shall have the following meanings unless the context clearly indicates otherwise:

"Algicides" means chemical substances, most commonly copper-based, used as a treatment method to control algae growths.

"Board" means State Water Control Board. When used outside the context of the promulgation of regulations, including regulations to establish general permits, "board" means the Department of Environmental Quality.

"Chesapeake Bay and its tidal tributaries" means all tidally influenced waters of the Chesapeake Bay; western and eastern coastal embayments and tributaries; James, York, Rappahannock and Potomac Rivers and all their tidal tributaries to the end of tidal waters in each tributary (in larger rivers this is the fall line); and includes subdivisions 1, 2, 3, 4, 5, and 6 of 9VAC25-260-390, subdivisions 1, 1b, 1d, 1f and 1o of 9VAC25-260-410, subdivisions 5 and 5a of 9VAC25-260-415, subdivisions 1 and 1a of 9VAC25-260-440, subdivisions 2, 3, 3a, 3b and 3e of 9VAC25-260-520, and subdivision 1 of 9VAC25-260-530. This definition does not include free flowing sections of these waters.

"Criteria" means elements of the board's water quality standards, expressed as constituent concentrations, levels, or narrative statements, representing a quality of water that supports a particular use. When criteria are met, water quality will generally protect the designated use.

"Department" or "DEQ" means the Virginia Department of Environmental Quality.

"Designated uses" means those uses specified in water quality standards for each waterbody or segment whether or not they are being attained.

"Drifting organisms" means planktonic organisms that are dependent on the current of the water for movement.

"Epilimnion" means the upper layer of nearly uniform temperature in a thermally stratified man-made lake or reservoir listed in 9VAC25-260-187 B.

"Existing uses" means those uses actually attained in the waterbody on or after November 28, 1975, whether or not they are included in the water quality standards.

"Lacustrine" means the zone within a lake or reservoir that corresponds to nonflowing lake-like conditions such as those near the dam. The other two zones within a reservoir are riverine (flowing, river-like conditions) and transitional (transition from river to lake conditions).

"Man-made lake or reservoir" means a constructed impoundment.

"Mixing zone" means a limited area or volume of water where initial dilution of a discharge takes place and where numeric water quality criteria can be exceeded but designated uses in the waterbody on the whole are maintained and lethality is prevented.

"Natural lake" means an impoundment that is natural in origin. There are two natural lakes in Virginia: Mountain Lake in Giles County and Lake Drummond located within the boundaries of Chesapeake and Suffolk in the Great Dismal Swamp.

"Passing organisms" means free swimming organisms that move with a mean velocity at least equal to the ambient current in any direction.

"Primary contact recreation" means any water-based form of recreation, the practice of which has a high probability for total body immersion or ingestion of water (examples include but are not limited to swimming, water skiing, canoeing and kayaking).

"Pycnocline" means the portion of the water column where density changes rapidly because of salinity and/or temperature. In an estuary the pycnocline is the zone separating deep, cooler more saline waters from the less saline, warmer surface waters. The upper and lower boundaries of a pycnocline are measured as a change in density per unit of depth that is greater than twice the change of the overall average for the total water column.

"Secondary contact recreation" means a water-based form of recreation, the practice of which has a low probability for total body immersion or ingestion of waters (examples include but are not limited to wading, boating and fishing).

"Swamp waters" means waters with naturally occurring low pH and low dissolved oxygen caused by (i) low flow velocity that prevents mixing and reaeration of stagnant, shallow waters and (ii) decomposition of vegetation that lowers dissolved oxygen concentrations and causes tannic acids to color the water and lower the pH.

"Use attainability analysis" means a structured scientific assessment of the factors affecting the attainment of the use which may include physical, chemical, biological, and economic factors as described in 9VAC25-260-10 H.

"Water quality standards" means provisions of state or federal law which consist of a designated use or uses for the waters of the Commonwealth and water quality criteria for such waters based upon such uses. Water quality standards are to protect the public health or welfare, enhance the quality of water and serve the purposes of the State Water Control Law (§ 62.1-44.2 et seq. of the Code of Virginia) and the federal Clean Water Act (33 USC § 1251 et seq.).

"Wetlands" means those areas that are inundated or saturated by surface water or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia; Clean Water Act (33 USC § 1251 et seq.); 40 CFR Part 131.

Historical Notes

Derived from Virginia Register Volume 14, Issue 4, eff. December 10, 1997; amended, Virginia Register Volume 19, Issue 7, eff. January 15, 2003; Volume 20, Issue 9, eff. February 12, 2004; Errata 20:11 VA.R. 1387 February 9, 2004; amended, Virginia Register Volume 21, Issue 23, eff. June 24, 2005; Volume 24, Issue 4, eff. August 14, 2007; Volume 32, Issue 26, eff. June 27, 2017; Volume 39, Issue 5, eff. November 23, 2022.

9VAC25-260-10. Designation of uses.

A. All state waters, including wetlands, are designated for the following uses: recreational uses, e.g., swimming and boating; the propagation and growth of a balanced, indigenous population of aquatic life, including game fish, which might reasonably be expected to inhabit them; wildlife; and the production of edible and marketable natural resources, e.g., fish and shellfish.

B. Subcategories of the propagation and growth of a balanced indigenous population of aquatic life, including game fish designated use for waters in the Chesapeake Bay and its tidal tributaries are listed in this subsection.

1. Migratory Fish Spawning and Nursery Designated Use: waters in the Chesapeake Bay and its tidal tributaries that protect the survival, growth and propagation of the early life stages of a balanced, indigenous population of anadromous, semi-anadromous, catadromous and tidal-fresh resident fish species inhabiting spawning and nursery grounds. This designated use extends from the end of tidal waters to the downriver end of spawning and nursery habitats that have been determined through a composite of all targeted anadromous and semi-anadromous fish species' spawning and nursery habitats (see boundaries in U.S. Environmental Protection Agency, 2004, Technical Support Document for Identification of Chesapeake Bay Designated Uses and Attainability 2004 Addendum, Chesapeake Bay Program Office, Annapolis, Maryland). This designated use extends horizontally from the shoreline of the body of water to the adjacent shoreline, and extends down through the water column to the bottom water-sediment interface. This use applies February 1 through May 31 and applies in addition to the open-water use described in this subsection.

2. Shallow-water Submerged Aquatic Vegetation Designated Use: waters in the Chesapeake Bay and its tidal tributaries that support the survival, growth and propagation of submerged aquatic vegetation (rooted, underwater bay grasses). This use applies April 1 through October 31 in tidal-fresh, oligohaline and mesohaline Chesapeake Bay Program segments, and March 1 through November 30 in polyhaline Chesapeake Bay Program segments and applies in addition to the open-water use described in this subsection.

3. Open Water Aquatic Life Designated Use: waters in the Chesapeake Bay and its tidal tributaries that protect the survival, growth and propagation of a balanced, indigenous population of aquatic life inhabiting open-water habitats. This designated use applies year-round but the vertical boundaries change seasonally. October 1 through May 31, the open water aquatic life use extends horizontally from the shoreline at mean low water, to the adjacent shoreline, and extending through the water column to the bottom water-sediment interface. June 1 through September 30, if a pycnocline is present and, in combination with bottom bathymetry and water column circulation patterns, presents a barrier to oxygen replenishment of deeper waters, this designated use extends down into the water column only as far as the upper boundary of the pycnocline. June 1 through September 30, if a pycnocline is present but other physical circulation patterns (such as influx of oxygen rich oceanic bottom waters) provide for oxygen replenishment of deeper waters, the open-water aquatic life designated use extends down into the bottom water-sediment interface (see boundaries in U.S. Environmental Protection Agency, 2004 Technical Support Document for Identification of Chesapeake Bay Designated Uses and Attainability 2004 Addendum, Chesapeake Bay Program Office, Annapolis, Maryland). This designated use includes the migratory fish spawning and nursery and shallow-water submerged aquatic vegetation uses.

4. Deep Water Aquatic Life Designated Use: waters in the Chesapeake Bay and its tidal tributaries that protect the survival and growth of a balanced, indigenous population of aquatic life inhabiting deep-water habitats. This designated use extends to the tidally influenced waters located between the upper and lower boundaries of the pycnocline where, in combination with bottom bathymetry and water circulation patterns, a pycnocline is present and presents a barrier to oxygen replenishment of deeper waters. In some areas, the deep-water designated use extends from the upper boundary of the pycnocline down to the bottom water-sediment interface (see boundaries in U.S. Environmental Protection Agency, 2004 Technical Support Document for Identification of Chesapeake Bay Designated Uses and Attainability 2004 Addendum, Chesapeake Bay Program Office, Annapolis, Maryland). This use applies June 1 through September 30.

5. Deep Channel Seasonal Refuge Designated Use: waters in the Chesapeake Bay and its tidal tributaries that protect the survival of a balanced, indigenous population of benthic infauna and epifauna inhabiting deep-channel habitats. This designated use extends to the tidally influenced waters at depths greater than the lower boundary of the pycnocline in areas where, in combination with bottom bathymetry and water circulation patterns, the pycnocline presents a barrier to oxygen replenishment of deeper waters (see boundaries in U.S. Environmental Protection Agency, 2004 Technical Support Document for Identification of Chesapeake Bay Designated Uses and Attainability 2004 Addendum, Chesapeake Bay Program Office, Annapolis, Maryland). This use applies June 1 through September 30.

C. In designating uses of a water body and the appropriate criteria for those uses, the board shall take into consideration the water quality standards of downstream waters and shall ensure that its water quality standards provide for the attainment and maintenance of the water quality standards of downstream waters.

D. The board may adopt subcategories of a use and set the appropriate criteria to reflect varying needs of such subcategories of uses, for instance, to differentiate between cold water (trout streams) and warm water fisheries.

E. At a minimum, uses are deemed attainable if they can be achieved by the imposition of effluent limits required under §§ 301(b)(1)(A) and (B) and 306 of the Clean Water Act and cost-effective and reasonable best management practices for nonpoint source control.

F. Prior to adding or removing any use, or establishing subcategories of a use, the board shall provide notice and an opportunity for a public hearing under the Administrative Process Act (§ 2.2-4000 et seq. of the Code of Virginia).

G. The board may adopt seasonal uses as an alternative to reclassifying a water body or segment thereof to uses requiring less stringent water quality criteria. If seasonal uses are adopted, water quality criteria should be adjusted to reflect the seasonal uses; however, such criteria shall not preclude the attainment and maintenance of a more protective use in another season.

H. The board may remove a designated use which is not an existing use, or establish subcategories of a use, if the board can demonstrate that attaining the designated use is not feasible because:

1. Naturally occurring pollutant concentrations prevent the attainment of the use;

2. Natural, ephemeral, intermittent or low flow conditions or water levels prevent the attainment of the use unless these conditions may be compensated for by the discharge of sufficient volume of effluent discharges without violating state water conservation requirements to enable uses to be met;

3. Human caused conditions or sources of pollution prevent the attainment of the use and cannot be remedied or would cause more environmental damage to correct than to leave in place;

4. Dams, diversions or other types of hydrologic modifications preclude the attainment of the use, and it is not feasible to restore the water body to its original condition or to operate such modification in a way that would result in the attainment of the use;

5. Physical conditions related to the natural features of the water body, such as the lack of a proper substrate, cover, flow, depth, pools, riffles, and the like, unrelated to water quality, preclude attainment of aquatic life protection uses; or

6. Controls more stringent than those required by §§ 301(b) and 306 of the Clean Water Act would result in substantial and widespread economic and social impact.

I. The board may not remove designated uses if:

1. They are existing uses, unless a use requiring more stringent criteria is added; or

2. Such uses will be attained by implementing effluent limits required under §§ 301(b)(1)(A) and (B) and 306 of the Clean Water Act and by implementing cost-effective and reasonable best management practices for nonpoint source control.

J. Where existing water quality standards specify designated uses less than those which are presently being attained, the board shall revise its standards to reflect the uses actually being attained.

K. The board must conduct a use attainability analysis whenever:

1. The board designates or has designated uses that do not include the uses specified in § 101(a)(2) of the Clean Water Act; or

2. The board wishes to remove a designated use that is specified in § 101(a)(2) of the Clean Water Act or to adopt subcategories of uses specified in § 101(a)(2) of the Clean Water Act which require less stringent criteria.

L. The board is not required to conduct a use attainability analysis under this chapter whenever designating uses which include those specified in subsection A of this section.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia; 33 USC § 1251 et seq. of the federal Clean Water Act; 40 CFR Part 131.

Historical Notes

Derived from VR680-21-01.1, eff. May 20, 1992; amended, Virginia Register Volume 14, Issue 4, eff. December 10, 1997; Volume 20, Issue 9, eff. February 12, 2004; Volume 21, Issue 23, eff. June 24, 2005; Volume 26, Issue 12, eff. February 1, 2010.

9VAC25-260-20. General criteria.

A. State waters, including wetlands, shall be free from substances attributable to sewage, industrial waste, or other waste in concentrations, amounts, or combinations which contravene established standards or interfere directly or indirectly with designated uses of such water or which are inimical or harmful to human, animal, plant, or aquatic life.

Specific substances to be controlled include, but are not limited to: floating debris, oil, scum, and other floating materials; toxic substances (including those which bioaccumulate); substances that produce color, tastes, turbidity, odors, or settle to form sludge deposits; and substances which nourish undesirable or nuisance aquatic plant life. Effluents which tend to raise the temperature of the receiving water will also be controlled. Conditions within mixing zones established according to 9VAC25-260-20 B do not violate the provisions of this subsection.

B. The board may use mixing zone concepts in evaluating limitations for Virginia Pollutant Discharge Elimination System permits.

1. Mixing zones evaluated or established by the board in fresh water shall not:

a. Prevent movement of or cause lethality to passing and drifting aquatic organisms through the water body in question;

b. Constitute more than one half of the width of the receiving watercourse nor constitute more than one third of the area of any cross section of the receiving watercourse;

c. Extend downstream at any time a distance more than five times the width of the receiving watercourse at the point of discharge.

2. Mixing zones evaluated or established by the board in open ocean, estuarine and transition zone waters (see 9VAC25-260-140 C) shall not:

a. Prevent movement of or cause lethality to passing and drifting aquatic organisms through the water body in question;

b. Extend more than five times in any direction the average depth along a line extending 1/3 of the way across the receiving water from the discharge point to the opposite shore.

3. A subsurface diffuser shall be required for any new or expanded freshwater discharge greater than or equal to 0.5 MGD to open ocean, estuarine and transition zone waters (see 9VAC25-260-140 C) and the acute and chronic criteria shall be met at the edge of the zone of initial mixing. The zone of initial mixing is the area where mixing of ambient water and effluent is driven by the jet effect and/or momentum of the effluent. Beyond this zone the mixing is driven by ambient turbulence.

4. Mixing zones shall not be allowed by the board for effluents discharged to wetlands, swamps, marshes, lakes or ponds.

5. An allocated impact zone may be allowed within a mixing zone. This zone is the area of initial dilution of the effluent with the receiving water where the concentration of the effluent will be its greatest in the water column. Mixing within these allocated impact zones shall be as quick as practical and shall be sized to prevent lethality to passing and drifting aquatic organisms. The acute aquatic life criteria are not required to be attained in the allocated impact zone.

6. Mixing zones shall be evaluated or established such that acute criteria are met outside the allocated impact zone and chronic criteria are met at the edge of the mixing zone.

7. No mixing zone shall be used for, or considered as, a substitute for minimum treatment technology required by the Clean Water Act and other applicable state and federal laws.

8. The board shall not approve a mixing zone that violates the federal Endangered Species Act of 1973 (16 USCA §§ 1531-1543) or the Virginia Endangered Species Act, Article 6 (§ 29.1-563 et seq.) of Chapter 5 of Title 29.1 of the Code of Virginia.

9. Mixing zones shall not be allowed for the bacteria criteria in 9VAC25-260-170.

10. The board may waive the requirements of subdivisions 1 b and c, 2 b, 3 and 4 of this subsection on a case-by-case basis if:

a. The board determines that a complete mix assumption is appropriate; or

b. A discharger provides an acceptable demonstration of:

(1) Information defining the actual boundaries of the mixing zone in question; and

(2) Information and data demonstrating no violation of subdivisions B 1 a, 2 a and B 7 of this subsection by the mixing zone in question.

11. The size of a thermal mixing zone shall be determined on a case-by-case basis. This determination shall be based upon a sound rationale and be supported by substantial biological, chemical, physical, and engineering evidence and analysis. Any such determination shall show to the board's satisfaction that no adverse changes in the protection and propagation of balanced indigenous populations of fish, aquatic life, and wildlife may reasonably be expected to occur. A satisfactory showing made in conformance with § 316(a) of the Clean Water Act shall be deemed as compliance with the requirements of this section.

12. Notwithstanding the above, no new or expanded mixing zone shall:

a. Be allowed in waters listed in 9VAC25-260-30 A 3 c;

b. Be allowed in waters defined in 9VAC25-260-30 A 2 for new or existing discharges unless the requirements outlined in 9VAC25-260-30 A 2 are satisfied.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia; 33 USC § 1251 et seq. of the federal Clean Water Act; 40 CFR Part 131.

Historical Notes

Derived from VR680-21-01.2, eff. May 20, 1992; amended, Virginia Register Volume 14, Issue 4, eff. December 10, 1997; Errata, 14:12 VA.R. 1937 March 2, 1998; amended, Virginia Register Volume 20, Issue 9, eff. February 12, 2004; Volume 26, Issue 12, eff. February 1, 2010.

9VAC25-260-30. Antidegradation policy.

A. All surface waters of the Commonwealth shall be provided one of the following three levels, or tiers, of antidegradation protection. This antidegradation policy shall be applied whenever any activity is proposed that has the potential to affect existing surface water quality.

1. As a minimum, existing instream water uses and the level of water quality necessary to protect the existing uses shall be maintained and protected.

2. Where the quality of the waters exceed water quality standards, that quality shall be maintained and protected unless the board finds, after full satisfaction of the intergovernmental coordination and public participation provisions of the Commonwealth's continuing planning process, that allowing lower water quality is necessary to accommodate important economic or social development in the area in which the waters are located. In allowing such degradation or lower water quality, the board shall assure water quality adequate to protect existing uses fully. Further, the board shall assure that there shall be achieved the highest statutory and regulatory requirements applicable to all new or existing point source discharges of effluent and all cost-effective and reasonable best management practices for nonpoint source control.

3. Surface waters, or portions of these, which provide exceptional environmental settings and exceptional aquatic communities or exceptional recreational opportunities may be designated and protected as described in subdivisions 3 a, b and c of this subsection.

a. Designation procedures.

(1) Designations shall be adopted in accordance with the provisions of the Administrative Process Act (§ 2.2-4000 et seq. of the Code of Virginia) and the board's public participation guidelines.

(2) Upon receiving a nomination of a waterway or segment of a waterway for designation as an exceptional state water pursuant to the board's antidegradation policy, as required by 40 CFR 131.12, the board shall notify each locality in which the waterway or segment lies and shall make a good faith effort to provide notice to impacted riparian property owners. The written notice shall include, at a minimum: (i) a description of the location of the waterway or segment; (ii) the procedures and criteria for designation as well as the impact of the designation; (iii) the name of the person making the nomination; and (iv) the name of a contact person at the Department of Environmental Quality who is knowledgeable about the nomination and the waterway or segment. Notice to property owners shall be based on names and addresses taken from local tax rolls. Such names and addresses shall be provided by the Commissioners of the Revenue or the tax assessor's office of the affected jurisdiction upon request by the board. After receipt of the notice of the nomination, localities shall be provided 60 days to comment on the consistency of the nomination with the locality's comprehensive plan. The comment period established by subdivision 3 a (2) of this subsection shall in no way impact a locality's ability to comment during any additional comment periods established by the board.

b. Implementation procedures.

(1) The quality of waters designated in subdivision 3 c of this subsection shall be maintained and protected to prevent permanent or long-term degradation or impairment.

(2) No new, additional, or increased discharge of sewage, industrial wastes or other pollution into waters designated in subdivision 3 c of this subsection shall be allowed.

(3) Activities causing temporary sources of pollution may be allowed in waters designated in subdivision 3 c of this subsection even if degradation may be expected to temporarily occur provided that after a minimal period of time the waters are returned or restored to conditions equal to or better than those existing just prior to the temporary source of pollution.

c. Surface waters designated under this subdivision are as follows:

(1) Little Stony Creek in Giles County from the first footbridge above the Cascades picnic area, upstream to the 3,300-foot elevation.

(2) Bottom Creek in Montgomery County and Roanoke County from Route 669 (Patterson Drive) downstream to the last property boundary of the Nature Conservancy on the southern side of the creek.

(3) Lake Drummond, located on U.S. Fish and Wildlife Service property, in its entirety within the cities of Chesapeake and Suffolk excluding any ditches and/or tributaries.

(4) North Creek in Botetourt County from the first bridge above the United States Forest Service North Creek Camping Area to its headwaters.

(5) Brown Mountain Creek, located on U.S. Forest Service land in Amherst County, from the City of Lynchburg property boundary upstream to the first crossing with the national forest property boundary.

(6) Laurel Fork, located on U.S. Forest Service land in Highland County, from the national forest property boundary below Route 642 downstream to the Virginia/West Virginia state line.

(7) North Fork of the Buffalo River, located on U.S. Forest Service land in Amherst County, from its confluence with Rocky Branch upstream to its headwaters.

(8) Pedlar River, located on U.S. Forest Service land in Amherst County, from where the river crosses FR 39 upstream to the first crossing with the national forest property boundary.

(9) Ramseys Draft, located on U.S. Forest Service land in Augusta County, from its headwaters (which includes Right and Left Prong Ramseys Draft) downstream to the Wilderness Area boundary.

(10) Whitetop Laurel Creek, located on U.S. Forest Service land in Washington County, from the national forest boundary immediately upstream from the second railroad trestle crossing the creek above Taylors Valley upstream to the confluence of Green Cove Creek.

(11) Ragged Island Creek in Isle of Wight County from its confluence with the James River at a line drawn across the creek mouth at N36°56.306'/W76°29.136' to N36°55.469'/W76°29.802' upstream to a line drawn across the main stem of the creek at N36°57.094'/W76°30.473' to N36°57.113'/W76°30.434', excluding wetlands and impounded areas and including only those tributaries completely contained within the Ragged Island Creek Wildlife Management Area on the northeastern side of the creek.

(12) Big Run in Rockingham County from its headwaters downstream to the first crossing with the Shenandoah National Park boundary and all tributaries to this segment of Big Run within the confines of Shenandoah National Park.

(13) Doyles River in Albemarle County from its headwaters to the first crossing with the Shenandoah National Park boundary and Jones Falls Run from its headwaters to its confluence with Doyles River and all tributaries to these segments of Doyles River and Jones Fall Run within the confines of Shenandoah National Park.

(14) East Hawksbill Creek in Page County from its headwaters downstream to the first crossing with the Shenandoah National Park boundary and all tributaries to this segment of East Hawksbill Creek within the confines of Shenandoah National Park.

(15) Jeremys Run in Page County from its headwaters downstream to the first crossing with the Shenandoah National Park boundary and all tributaries to this segment of Jeremys Run within the confines of Shenandoah National Park.

(16) East Branch Naked Creek in Page County from its headwaters downstream to the first crossing with the Shenandoah National Park boundary and all tributaries to this segment of East Branch Naked Creek within the confines of Shenandoah National Park.

(17) Piney River in Rappahannock County from its headwaters downstream to the first crossing with the Shenandoah National Park boundary and all tributaries to this segment of the Piney River within the confines of Shenandoah National Park.

(18) North Fork Thornton River in Rappahannock County from its headwaters downstream to the first crossing with the Shenandoah National Park boundary and all tributaries to this segment of the North Fork Thornton River within the confines of Shenandoah National Park.

(19) Blue Suck Branch from its headwaters downstream to the first crossing with the George Washington National Forest boundary.

(20) Downy Branch from its headwaters downstream to the first crossing with the George Washington National Forest boundary.

(21) North Branch Simpson Creek (Brushy Run) from its headwaters downstream to its confluence with Simpson Creek.

(22) Roberts Creek from its confluence with the Pedlar River upstream to its first crossing with the National Forest boundary.

(23) Shady Mountain Creek from its headwaters downstream to its confluence with the Pedlar River.

(24) Cove Creek from its headwaters downstream to the National Forest boundary.

(25) Little Cove Creek and its tributaries from the headwaters downstream to the National Forest boundary.

(26) Rocky Branch from its headwaters downstream to its confluence with the North Fork of the Buffalo River.

(27) North Fork of the Buffalo River from its confluence with Rocky Branch downstream to the National Forest Boundary.

(28) The Hazel River in Rappahannock County from its headwaters to the first downstream crossing with the Shenandoah National Park boundary and all tributaries within this segment within the confines of Shenandoah National Park.

(29) Little Stony Creek in Scott County from Bark Camp Lake dam to its confluence with Bakers Branch.

(30) North River in Augusta County from the Staunton Reservoir dam to the first crossing with National Forest lands boundary (near Girl Scout Camp May Flather).

B. Any determinations concerning thermal discharge limitations made under § 316(a) of the Clean Water Act will be considered to be in compliance with the antidegradation policy.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia; 33 USC § 1251 et seq. of the federal Clean Water Act; 40 CFR Part 131.

Historical Notes

Derived from VR680-21-01.3, eff. May 20, 1992; amended, Virginia Register Volume 13, Issue 11, eff. March 19, 1997; Volume 13, Issue 14, eff. April 30, 1997; Volume 14, Issue 4, eff. December 10, 1997; Volume 14, Issue 9, eff. February 18, 1998; Volume 20, Issue 9, eff. February 12, 2004; Volume 21, Issue 22, eff. August 10, 2005; Volume 22, Issue 10, eff. December 29, 2005; Volume 24, Issue 2, eff. September 11, 2007; Volume 24, Issue 26, eff. August 12, 2008; Volume 25, Issue 5, eff. October 22, 2008; Volume 26, Issue 12, eff. February 1, 2010.

9VAC25-260-40. Stream flow.

Man-made alterations in stream flow shall not contravene designated uses including protection of the propagation and growth of aquatic life.

Statutory Authority

§ 62.1-44.15(3a) of the Code of Virginia.

Historical Notes

Derived from VR680-21-01.4, eff. May 20, 1992; amended, Virginia Register Volume 14, Issue 4, eff. December 10, 1997.

9VAC25-260-50. Numerical criteria for dissolved oxygen, pH, and maximum temperature***.

*This classification recognizes that the natural quality of these waters may fluctuate outside of the values for D.O. and pH set forth above as water quality criteria in Class I through VI waters. The natural quality of these waters is the water quality found or expected in the absence of human-induced pollution. Water quality standards will not be considered violated when conditions are determined by the board to be natural and not due to human-induced sources. The board may develop site specific criteria for Class VII waters that reflect the natural quality of the waterbody when the evidence is sufficient to demonstrate that the site specific criteria rather than narrative criterion will fully protect aquatic life uses. Virginia Pollutant Discharge Elimination System limitations in Class VII waters shall not cause significant changes to the naturally occurring dissolved oxygen and pH fluctuations in these waters.

**Maximum temperature will be the same as that for Classes I through VI waters as appropriate.

***The water quality criteria in this section do not apply below the lowest flow averaged (arithmetic mean) over a period of seven consecutive days that can be statistically expected to occur once every 10 climatic years (a climatic year begins April 1 and ends March 31). See 9VAC25-260-310 and 9VAC25-260-380 through 9VAC25-260-540 for site specific adjustments to these criteria.

****For a thermally stratified man-made lake or reservoir in Class III, IV, V, or VI waters that are listed in 9VAC25-260-187, these dissolved oxygen and pH criteria apply only to the epilimnion of the waterbody. When these waters are not stratified, the dissolved oxygen and pH criteria apply throughout the water column.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia; Clean Water Act (33 USC § 1251 et seq.); 40 CFR Part 131.

Historical Notes

Derived from VR680-21-01.5, eff. May 20, 1992; amended, Virginia Register Volume 14, Issue 4, eff. December 10, 1997; Volume 17, Issue 16 and Volume 18, Issue 17, eff. June 5, 2002; Volume 20, Issue 9, eff. February 12, 2004; Volume 21, Issue 23, eff. June 24, 2005; Volume 23, Issue 26, eff. August 14, 2007; Volume 26, Issue 12, eff. February 1, 2010; Volume 32, Issue 26, eff. June 27, 2017; Volume 39, Issue 9, eff. April 18, 2023.

9VAC25-260-55. (Repealed.)

Historical Notes

Derived from Virginia Register Volume 17, Issue 16 and Volume 18, Issue 17, eff. June 5, 2002; repealed, Volume 26, Issue 12, eff. February 1, 2010.

9VAC25-260-60. Rise above natural temperature.

Any rise above natural temperature shall not exceed 3°C except in the case of Class VI waters (natural trout waters), where it shall not exceed 1°C. However, the board can, on a case-by-case basis, impose a more stringent limit on the rise above natural temperature. Natural temperature is defined as that temperature of a body of water (measured as the arithmetic average over one hour) due solely to natural conditions without the influence of any point-source discharge.

Statutory Authority

§§ 62.1-44.15(3) and (10) of the Code of Virginia.

Historical Notes

Derived from VR680-21-01.6, eff. May 20, 1992.

9VAC25-260-70. Maximum hourly temperature change.

The maximum hourly temperature change shall not exceed 2°C, except in the case of Class VI waters (natural trout waters) where it shall not exceed 0.5°C. These criteria shall apply beyond the boundaries of mixing zones and are in addition to temperature changes caused by natural conditions.

Statutory Authority

§ 62.1-44.15(3a) of the Code of Virginia.

Historical Notes

Derived from VR680-21-01.7, eff. May 20, 1992; amended, Virginia Register Volume 14, Issue 4, eff. December 10, 1997.

9VAC25-260-80. Thermal discharges into lakes and impoundments.

In lakes and impoundments receiving thermal discharges, the temperature of the epilimnion, or surface water when there is no stratification, shall not be raised more than 3°C above that which existed before the addition of heat of artificial origin. The board may, on a case-by-case basis, impose a more stringent limit on temperature rise. The increase shall be based on the monthly average of the maximum daily temperature. The temperature of releases from these lakes and impoundments shall be consistent with standards established for the receiving waters. When an applicant for a permit proposes either a discharge of heated effluent into the hypolimnion or the pumping of water from the hypolimnion for return back into the same body of water, such practice shall not be approved unless a special study shows that the practice will not produce adverse effects.

Statutory Authority

§ 62.1-44.15(3a) of the Code of Virginia.

Historical Notes

Derived from VR680-21-01.8, eff. May 20, 1992; amended, Virginia Register Volume 14, Issue 4, eff. December 10, 1997.

9VAC25-260-90. Thermal variances.

The temperature limits set forth in 9VAC25-260-50 through 9VAC25-260-80 may be superseded in certain locations where a thermal variance demonstration is performed in accordance with § 316(a) of the Clean Water Act.

A successful demonstration accepted by the board concerning thermal discharge limits carried out under § 316(a) of the Clean Water Act shall constitute compliance with the temperature requirements of these standards. A successful demonstration must assure the protection and propagation of a balanced indigenous population of aquatic species and wildlife in or on the water into which the discharge is made. When making a determination concerning thermal discharge limits under § 316(a) of the Clean Water Act, the board shall provide notice and opportunity for a public hearing.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia; 33 USC § 1251 et seq. of the federal Clean Water Act; 40 CFR Part 131.

Historical Notes

Derived from VR680-21-01.9, eff. May 20, 1992; amended, Virginia Register Volume 14, Issue 4, eff. December 10, 1997; Volume 26, Issue 12, eff. February 1, 2010.

9VAC25-260-100. [Deleted].

Historical Notes

Derived from VR680-21-01, eff. May 20, 1992.

9VAC25-260-110. Halogen ban.

A. Chlorine or other halogen compounds Bromine, bromine chloride, hypochlorite and chlorine dioxide. shall not be used for disinfection purposes or other treatment purposes including biocide applications for any treatment facility with a permitted flow of 20,000 gallons per day or more discharging to waters containing endangered or threatened species listed in subsection C of this section or to waters listed as i and ii in the River Basin Section Tables, 9VAC25-260-390 et seq. except for dischargers who intermittently chlorinate. Dischargers of less than 20,000 gallons per day shall dechlorinate to the requirements of the numerical chlorine criteria in 9VAC25-260-140 B or to a nondetectable chlorine residual. Dischargers who intermittently chlorinate (not more than two hours in any eight-hour period) shall be required to install equipment or employ procedures, or both, to ensure dechlorination to a chlorine residual that meets the numerical chlorine criteria in 9VAC25-260-140 B, and to apply effective best management practices for chlorine. Dischargers who intermittently chlorinate shall, in order to address a possible malfunction of the dechlorination system, either have storage sufficient to contain the chlorinated water until it can be dechlorinated prior to discharge or have an online redundant and operational back-up dechlorination system.

B. Variance to this requirement shall not be made unless it has been affirmatively demonstrated that the existing uses of the water will be maintained and that either a change is justifiable to provide necessary economic or social development or the degree of waste treatment necessary to preserve the existing quality cannot be economically or socially justified.

C. TENNESSEE AND BIG SANDY RIVER BASINS

CLINCH RIVER SUBBASIN

Powell River from river mile 136 (south of Jonesville) downstream to the Tennessee/Virginia line (river mile 115.8—total 20.2 miles).

Endangered Species:

Threatened Species:

Clinch River from river mile 323 (Richlands) downstream to the Tennessee/Virginia line (river mile 202.1).

Endangered Species:

Clinch River from the Scott/Russell County line (at Bangor—river mile 244.2) downstream to the Tennessee boundary (river mile 202.1).

Threatened Species:

Copper Creek from 2 miles above its confluence with the Clinch River (river mile 211.6).

Endangered Species:

Copper Creek from Dickensville (river mile 56) in Russell County downstream to its confluence with the Clinch River.

Threatened Species:

HOLSTON RIVER SUBBASIN

North Fork Holston River from river mile 93.3 (near Broadford) downstream to the Smyth/Washington County line (river mile 82.1).

Endangered Species:

North Fork Holston River from the Smyth/Washington County line (river mile 82.1) to the Tennessee/Virginia boundary (river mile 5).

Threatened Species:

Middle Fork Holston River from river mile 43 (in Marion) downstream to river mile 18.4.

Endangered Species:

Middle Fork Holston River from river mile 6.5 to river mile 3.2 near Osceola.

Threatened Species:

Statutory Authority

§ 62.1-44.15(3a) of the Code of Virginia.

Historical Notes

Derived from VR680-21-01.11, eff. May 20, 1992; amended, Virginia Register Volume 14, Issue 4, eff. December 10, 1997; Errata, 14:12 VA.R. 1937 March 2, 1998.

9VAC25-260-120. (Repealed.)

Historical Notes

Derived from VR680-21-01.12 and VR680-21-01.13, eff. May 20, 1992; repealed, Virginia Register Volume 14, Issue 4, eff. December 10, 1997.

9VAC25-260-140. Criteria for surface water.

A. Instream water quality conditions shall not be acutely¹ or chronically² toxic except as allowed in 9VAC25-260-20 B (mixing zones). The following are definitions of acute and chronic toxicity conditions:

"Acute toxicity" means an adverse effect that usually occurs shortly after exposure to a pollutant. Lethality to an organism is the usual measure of acute toxicity. Where death is not easily detected, immobilization is considered equivalent to death.

"Chronic toxicity" means an adverse effect that is irreversible or progressive or occurs because the rate of injury is greater than the rate of repair during prolonged exposure to a pollutant. This includes low level, long-term effects such as reduction in growth or reproduction.

B. The following table is a list of numerical water quality criteria for specific parameters.

C. Application of freshwater and saltwater numerical criteria. The numerical water quality criteria listed in subsection B of this section (excluding dissolved oxygen, pH, temperature) shall be applied according to the following classes of waters (see 9VAC25-260-50) and boundary designations:

The following describes the boundary designations for Class II, (estuarine, transition zone and tidal freshwater waters) by river basin:

1. Rappahannock Basin. Tidal freshwater is from the fall line of the Rappahannock River to the upstream boundary of the transition zone including all tidal tributaries that enter the tidal freshwater Rappahannock River.

Transition zone upstream boundary – N38° 4' 56.59"/W76° 58' 47.93" (430 feet east of Hutchinson Swamp) to N38° 5' 23.33"/W76° 58' 24.39" (0.7 miles upstream of Peedee Creek).

Transition zone downstream boundary – N37° 58' 45.80"/W76° 55' 28.75" (1,000 feet downstream of Jenkins Landing) to N37° 59' 20.07/W76° 53' 45.09" (0.33 miles upstream of Mulberry Point). All tidal waters that enter the transition zone are themselves transition zone waters.

Estuarine waters are from the downstream boundary of the transition zone to the mouth of the Rappahannock River (Buoy 6), including all tidal tributaries that enter the estuarine waters of the Rappahannock River.

2. York Basin. Tidal freshwater is from the fall line of the Mattaponi River at N37° 47' 20.03"/W77° 6' 15.16" (800 feet upstream of the Route 360 bridge in Aylett) to the upstream boundary of the Mattaponi River transition zone, and from the fall line of the Pamunkey River at N37° 41' 22.64"/W77° 12' 50.83" (2,000 feet upstream of Totopotomy Creek) to the upstream boundary of the Pamunkey River transition zone, including all tidal tributaries that enter the tidal freshwaters of the Mattaponi and Pamunkey Rivers.

Mattaponi River transition zone upstream boundary – N37° 39' 29.65"/W76° 52' 53.29" (1,000 feet upstream of Mitchell Hill Creek) to N37° 39' 24.20"/W76° 52' 55.87" (across from Courthouse Landing).

Mattaponi River transition zone downstream boundary – N37° 32' 19.76"/W76° 47' 29.41" (old Lord Delaware Bridge, west side) to N37° 32' 13.25"/W76° 47' 10.30" (old Lord Delaware Bridge, east side).

Pamunkey River transition zone upstream boundary – N37° 32' 36.63"/W76° 58' 29.88" (Cohoke Marsh, 0.9 miles upstream of Turkey Creek) to N37° 32' 36.51"/W76° 58' 36.48" (0.75 miles upstream of creek at Cook Landing).

Pamunkey River transition zone downstream boundary – N37° 31' 57.90"/W76° 48' 38.22" (old Eltham Bridge, west side) to N37° 32' 6.25"/W76° 48' 18.82" (old Eltham Bridge, east side).

All tidal tributaries that enter the transition zones of the Mattaponi and Pamunkey Rivers are themselves in the transition zone.

Estuarine waters are from the downstream boundary of the transition zones of the Mattaponi and Pamunkey Rivers to the mouth of the York River (Tue Marsh Light) including all tidal tributaries that enter the estuarine waters of the York River.

3. James Basin. Tidal freshwater is from the fall line of the James River in the City of Richmond upstream of Mayo Bridge to the upstream boundary of the transition zone, including all tidal tributaries that enter the tidal freshwater James River.

James River transition zone upstream boundary – N37° 14' 28.25"/W76° 56' 44.47" (at Tettington) to N37° 13' 38.56"/W76° 56' 47.13" (0.3 miles downstream of Sloop Point).

Chickahominy River transition zone upstream boundary – N37° 25' 44.79"/W77° 1' 41.76" (Holly Landing).

Transition zone downstream boundary – N37° 12' 7.23"/W76° 37' 34.70" (near Carters Grove Home, 1.25 miles downstream of Grove Creek) to N37° 9' 17.23"/W76° 40' 13.45" (0.7 miles upstream of Hunnicutt Creek). All tidal waters that enter the transition zone are themselves transition zone waters.

Estuarine waters are from the downstream transition zone boundary to the mouth of the James River (Buoy 25) including all tidal tributaries that enter the estuarine waters of the James River.

4. Potomac Basin. Tidal freshwater includes all tidal tributaries that enter the Potomac River from its fall line at the Chain Bridge (N38° 55' 46.28"/W77° 6' 59.23") to the upstream transition zone boundary near Quantico, Virginia.

Transition zone includes all tidal tributaries that enter the Potomac River from N38° 31' 27.05"/W77° 17' 7.06" (midway between Shipping Point and Quantico Pier) to N38° 23' 22.78"/W77° 1' 45.50" (one mile southeast of Mathias Point).

Estuarine waters includes all tidal tributaries that enter the Potomac River from the downstream transition zone boundary to the mouth of the Potomac River (Buoy 44B).

5. Chesapeake Bay, Atlantic Ocean, and small coastal basins. Estuarine waters include the Atlantic Ocean tidal tributaries, and the Chesapeake Bay and its small coastal basins from the Virginia state line to the mouth of the bay (a line from Cape Henry drawn through Buoys 3 and 8 to Fishermans Island), and its tidal tributaries, excluding the Potomac tributaries and those tributaries listed in subdivisions 1 through 4 of this subsection.

6. Chowan River Basin. Tidal freshwater includes the Northwest River and its tidal tributaries from the Virginia-North Carolina state line to the free flowing portion, the Blackwater River and its tidal tributaries from the Virginia-North Carolina state line to the end of tidal waters at approximately state route 611 at river mile 20.90, the Nottoway River and its tidal tributaries from the Virginia-North Carolina state line to the end of tidal waters at approximately Route 674, and the North Landing River and its tidal tributaries from the Virginia-North Carolina state line to the Great Bridge Lock.

Transition zone includes Back Bay and its tributaries in the City of Virginia Beach to the Virginia-North Carolina state line.

D. Site-specific modifications to numerical water quality criteria.

1. The board may consider site-specific modifications to numerical water quality criteria in subsection B of this section where the applicant or permittee demonstrates that the alternate numerical water quality criteria are sufficient to protect all designated uses (see 9VAC25-260-10) of that particular surface water segment or body.

2. Any demonstration for site-specific human health criteria shall be restricted to a reevaluation of the bioconcentration or bioaccumulation properties of the pollutant. The exceptions to this restriction are for site-specific criteria for taste, odor, and aesthetic compounds noted by double asterisks in subsection B of this section and nitrates.

3. Procedures for promulgation and review of site-specific modifications to numerical water quality criteria resulting from subdivisions 1 and 2 of this subsection.

a. Proposals describing the details of the site-specific study shall be submitted to the board's staff for approval prior to commencing the study.

b. Any site-specific modification shall be promulgated as a regulation in accordance with the Administrative Process Act (§ 2.2-4000 et seq. of the Code of Virginia). All site-specific modifications shall be listed in 9VAC25-260-310 (Special standards and requirements).

E. Variances to water quality standards.

1. A variance from numeric criteria may be granted to a discharger if it can be demonstrated that one or more of the conditions in 9VAC25-260-10 H limit the attainment of one or more specific designated uses.

a. Variances shall apply only to the discharger to whom they are granted and shall be reevaluated and either continued, modified, or revoked at the time of permit issuance. At that time the permittee shall make a showing that the conditions for granting the variance still apply.

b. Variances shall be described in the public notice published for the permit. The decision to approve a variance shall be subject to the public participation requirements of the Virginia Pollutant Discharge Elimination System (VPDES) Permit Regulation, 9VAC25-31.

c. Variances shall not prevent the maintenance and protection of existing uses or exempt the discharger or regulated activity from compliance with other appropriate technology or water quality-based limits or best management practices.

d. Variances granted under this section shall not apply to new discharges.

e. Variances shall be submitted by the department's Division of Scientific Research or its successors to the U.S. Environmental Protection Agency for review and approval or disapproval.

f. A list of variances granted shall be maintained by the department's Division of Scientific Research or its successors.

2. None of the variances in this subsection shall apply to the halogen ban section (9VAC25-260-110) or temperature criteria in 9VAC25-260-50 if superseded by § 316(a) of the Clean Water Act requirements. No variances in this subsection shall apply to the criteria that are designed to protect human health from carcinogenic and noncarcinogenic toxic effects (subsection B of this section) with the exception of the metals, and the taste, odor, and aesthetic compounds noted by double asterisks and nitrates, listed in subsection B of this section.

F. Water effect ratio.

1. A water effects ratio (WER) shall be determined by measuring the effect of receiving water (as it is or will be affected by any discharges) on the bioavailability or toxicity of a metal by using standard test organisms and a metal to conduct toxicity tests simultaneously in receiving water and laboratory water. The ratio of toxicities of the metals in the two waters is the WER (toxicity in receiving water divided by toxicity in laboratory water equals WER). Once an acceptable WER for a metal is established, the numerical value for the metal in subsection B of this section is multiplied by the WER to produce an instream concentration that will protect designated uses. This instream concentration shall be utilized in permitting decisions.

2. The WER shall be assigned a value of 1.0 unless the applicant or permittee demonstrates to the department's satisfaction in a permit proceeding that another value is appropriate, or unless available data allow the department to compute a WER for the receiving waters. The applicant or permittee is responsible for proposing and conducting the study to develop a WER. The study may require multiple testing over several seasons. The applicant or permittee shall obtain the department's Division of Scientific Research or its successor approval of the study protocol and the final WER.

3. 9VAC25-31-230 C requires that permit limits for metals be expressed as total recoverable measurements. To that end, the study used to establish the WER may be based on total recoverable measurements of the metals.

4. The WER is established in a permit proceeding, shall be described in the public notice associated with the permit proceeding, and applies only to the applicant or permittee in that proceeding. The department's action to approve or disapprove a WER is a case decision, not an amendment to the present regulation.

The decision to approve or disapprove a WER shall be subject to the public participation requirements of Virginia Pollutant Discharge Elimination System (VPDES) Regulation, Part IV (9VAC25-31-260 et seq.). A list of final WERs will be maintained by the department's Division of Scientific Research or its successor.

5. A WER shall not be used for the freshwater and saltwater chronic mercury criteria or the freshwater acute and chronic selenium criteria.

G. Biotic Ligand Model for copper. On a case-by-case basis, EPA's 2007 copper criteria (EPA-822-F-07-001) biotic ligand model (BLM) for copper may be used to determine alternate copper criteria for freshwater sites. The BLM is a bioavailability model that uses receiving water characteristics to develop site-specific criteria. Site-specific data for 10 parameters are needed to use the BLM. These parameters are temperature, pH, dissolved organic carbon, calcium, magnesium, sodium, potassium, sulfate, chloride, and alkalinity. If sufficient data for these parameters are available, the BLM can be used to calculate alternate criteria values for the copper criteria. The BLM would be used instead of the hardness-based criteria and takes the place of the hardness adjustment and the WER. A WER will not be applicable with the BLM.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia; Clean Water Act (33 USC § 1251 et seq.); 40 CFR Part 131.

Historical Notes

Derived from VR680-21-01.14B, eff. May 20, 1992; amended, Virginia Register Volume 14, Issue 4, eff. December 10, 1997; Errata, 14:12 VA.R. 1937 March 2, 1998; amended, Virginia Register Volume 19, Issue 23, eff. August 27, 2003; Volume 20, Issue 9, eff. February 12, 2004; amended, Virginia Register Volume 26, Issue 12, eff. February 1, 2010; Errata, 26:12 VA.R. 2065 February 15, 2010; Volume 32, Issue 26, eff. July 27, 2017; amended Virginia Register Volume 36, Issue 6, eff. October 21, 2019; Errata,36:14 VA.R. 2053 March 2, 2020; amended Virginia Register Volume 39, Issue 9, eff. April 18, 2023; Volume 40, Issue 24, eff. June 26, 2024.

9VAC25-260-150. (Repealed.)

Historical Notes

Derived from VR680-21-01.15, eff. May 20, 1992; amended, Virginia Register Volume 14, Issue 4, eff. December 10, 1997; repealed, Virginia Register Volume 20, Issue 9, eff. February 12, 2004.

9VAC25-260-155. Ammonia surface water quality criteria.

A. The Department of Environmental Quality, after consultation with the Virginia Department of Wildlife Resources and the U.S. Fish and Wildlife Service, has determined that the majority of Virginia freshwaters are likely to contain, or have contained in the past, freshwater mussel species in the family Unionidae and contain early life stages of fish during most times of the year. Therefore, the ammonia criteria presented in subsections B and C of this section are designed to provide protection to these species and life stages. In an instance where it can be adequately demonstrated that either freshwater mussels or early life stages of fish are not present in a specific waterbody, potential options for alternate, site-specific criteria are presented in subsection D of this section. Acute criteria are a one-hour average concentration not to be exceeded more than once every three years¹ on the average, and chronic criteria are 30-day average concentrations not to be exceeded more than once every three years on the average.² In addition, the four-day average concentration of total ammonia nitrogen (in mg N/L) shall not exceed 2.5 times the chronic criterion within a 30-day period more than once every three years on the average.

¹The default design flow for calculating steady state wasteload allocations for the acute ammonia criterion for freshwater is the 1Q10 (see 9VAC25-260-140 B footnote 6) unless statistically valid methods are employed that demonstrate compliance with the duration and return frequency of the water quality criteria.

²The default design flow for calculating steady state wasteload allocations for the chronic ammonia criterion for freshwater is the 30Q10 (see 9VAC25-260-140 B footnote 6) unless statistically valid methods are employed which demonstrate compliance with the duration and return frequency of the water quality criteria.

B. The acute criteria for total ammonia (in mg N/L) for freshwaters with trout absent or present are in the following tables:

The acute criteria for trout present shall apply to all Class V-Stockable Trout Waters and Class VI-Natural Trout Waters as listed in 9VAC25-260-390 through 9VAC25-260-540. The acute criteria for trout absent apply to all other fresh waters.

To calculate total ammonia nitrogen acute criteria values in freshwater at different pH values than those listed in this subsection, use the following equations and round the result to two significant digits:

Where trout are absent:

Acute Criterion Concentration (mg N/L) =

Where MIN = 51.93 or 23.12 X 10^{0.036 X (20 – T)}, whichever is less

T = Temperature in ^oC

Or where trout are present, whichever of the following calculation results is less:

Acute Criterion Concentration (mg N/L) =

or

T = Temperature in ^oC

C. The chronic criteria for total ammonia nitrogen (in mg N/L) where freshwater mussels and early life stages of fish are present in freshwater are in the following table:

To calculate total ammonia nitrogen chronic criteria values in freshwater when freshwater mussels and early life stages of fish are present at different pH and temperature values than those listed in this subsection, use the following equation and round the result to two significant digits:

Chronic Criteria Concentration =

Where MAX = 7 or temperature in degrees Celsius, whichever is greater

T = temperature in °C

D. Site-specific considerations and alternate criteria. If it can be adequately demonstrated that freshwater mussels or early life stages of fish are not present at a site, then alternate site-specific criteria can be considered using the information provided in this subsection. Recalculated site-specific criteria shall provide for the attainment and maintenance of the water quality standards of downstream waters.

1. Site-specific modifications to the ambient water quality criteria for ammonia to account for the absence of freshwater mussels or early life stages of fish shall be conducted in accordance with the procedures contained in this subdivision. Because the department presumes that most state waterbodies have freshwater mussels and early life stages of fish present during most times of the year, the criteria shall be calculated assuming freshwater mussels and early life stages of fish are present using subsections B and C of this section unless the following demonstration that freshwater mussels or early life stages of fish are absent is successfully completed. Determination of the absence of freshwater mussels requires special field survey methods. This determination must be made after an adequate survey of the waterbody is conducted by an individual certified by the Virginia Department of Wildlife Resources for freshwater mussel identification and surveys. Determination of absence of freshwater mussels will be done in consultation with the Department of Wildlife Resources. Early life stages of fish are defined in subdivision 2 of this subsection. Modifications to the ambient water quality criteria for ammonia based on the presence or absence of early life stages of fish shall only apply at temperatures below 15°C.

a. During the review of any new or existing activity that has a potential to discharge ammonia in amounts that may cause or contribute to a violation of the ammonia criteria contained in subsection B of this section, the department may examine data from the following approved sources in subdivisions 1 a (1) through (5) of this subsection or may require the gathering of data in accordance with subdivisions 1 a (1) through (5) on the presence or absence of early life stages of fish in the affected waterbody.

(1) Species and distribution data contained in the Virginia Department of Wildlife Resources Wildlife Information System database.

(2) Species and distribution data contained in Freshwater Fishes of Virginia, 1994.

(3) Data and fish species distribution maps contained in Handbook for Fishery Biology, Volume 3, 1997.

(4) Field data collected in accordance with U.S. EPA's Rapid Bioassessment Protocols for Use in Streams and Wadeable Rivers, Second Edition, EPA 841-B-99-002. Field data must comply with all quality assurance and quality control criteria.

(5) The American Society for Testing and Materials (ASTM) Standard E-1241-88, Standard Guide for Conducting Early Life-Stage Toxicity Tests with Fishes.

b. If data or information from sources other than subdivisions 1 a (1) through (5) of this subsection are considered, then any resulting site-specific criteria modifications shall be reviewed and adopted in accordance with the site-specific criteria provisions in 9VAC25-260-140 D and submitted to EPA for review and approval.

c. If the department determines that the data and information obtained from subdivisions 1 a (1) through (5) of this subsection demonstrate that there are periods of each year when no early life stages are expected to be present for any species of fish that occur at the site, the department shall issue a notice to the public and make available for public comment the supporting data and analysis along with the department's preliminary decision to authorize the site-specific modification to the ammonia criteria. Such information shall include, at a minimum:

(1) Sources of data and information.

(2) List of fish species that occur at the site as defined in subdivision 3 of this subsection.

(3) Definition of the site. Definition of a "site" can vary in geographic size from a stream segment to a watershed to an entire eco-region.

(4) Duration of early life stage for each species in subdivision 1 c (2) of this subsection.

(5) Dates when early life stages of fish are expected to be present for each species in subdivision 1 c (2) of this subsection.

(6) Based on subdivision 1 c (5) of this subsection, identify the dates (beginning date, ending date), if any, where no early life stages are expected to be present for any of the species identified in subdivision 1 c (2) of this subsection.

d. If, after reviewing the public comments received in subdivision 1 c of this subsection and supporting data and information, the department determines that there are times of the year when no early life stages are expected to be present for any fish species that occur at the site, then the applicable ambient water quality criteria for ammonia for those time periods shall be calculated using the table in this subsection, or the formula for calculating the chronic criterion concentration for ammonia when early life stages of fish are absent.

e. The department shall maintain a comprehensive list of all sites where the department has determined that early life stages of fish are absent. For each site the list will identify the waterbodies affected and the corresponding times of the year that early life stages of fish are absent. This list is available either upon request from the Office of Water Quality Programs at 1111 East Main Street, Suite 1400 Richmond, VA 23219, or from the department website at https://www.deq.virginia.gov/our-programs/water/water-quality/standards.

2. The duration of the "early life stages" extends from the beginning of spawning through the end of the early life stages. The early life stages include the prehatch embryonic period, the post-hatch free embryo or yolk-sac fry, and the larval period, during which the organism feeds. Juvenile fish, which are anatomically similar to adults, are not considered an early life stage. The duration of early life stages can vary according to fish species. The department considers the sources of information in subdivisions 1 a (1) through (5) of this subsection to be the only acceptable sources of information for determining the duration of early life stages of fish under this procedure.

3. "Occur at the site" includes the species, genera, families, orders, classes, and phyla that are usually present at the site; are present at the site only seasonally due to migration; are present intermittently because they periodically return to or extend their ranges into the site; or were present at the site in the past or are present in nearby bodies of water, but are not currently present at the site due to degraded conditions, and are expected to return to the site when conditions improve. "Occur at the site" does not include taxa that were once present at the site but cannot exist at the site now due to permanent physical alteration of the habitat at the site.

4. Any modifications to ambient water quality criteria for ammonia in subdivision 1 of this subsection shall not likely jeopardize the continued existence of any federal or state listed, threatened, or endangered species or result in the destruction or adverse modification of such species' critical habitats.

5. Site-specific modifications to the ambient water quality criteria for ammonia to account for the absence of freshwater mussels shall be conducted in accordance with the procedures contained in this subsection. Because the department presumes that most state waterbodies have freshwater mussel species, the criteria shall be calculated assuming mussels are present using subsections B and C of this section unless the demonstration that freshwater mussels are absent is successfully completed and accepted by DEQ and the Department of Wildlife Resources.

6. Equations for calculating ammonia criteria for four different site-specific scenarios are provided in subdivisions 6 a through d of this subsection as follows: (i) acute criteria when mussels are absent but trout are present, (ii) acute criteria when mussels and trout are absent, (iii) chronic criteria when mussels are absent and early life stages of fish are present, and (iv) chronic criteria when mussels and early life stages of fish are absent. Additional information regarding site-specific criteria can be reviewed in appendix N (pages 225-242) of the EPA Aquatic Life Ambient Water Quality Criteria to Ammonia--Freshwater 2013 (EPA 822-R-13-001).

a. Acute criteria: freshwater mussels absent and trout present. To calculate total ammonia nitrogen acute criteria values (in mg N/L) in freshwater with freshwater mussels absent (procedures for making this determination are in subdivisions 1 through 5 of this subsection) and trout present, use the following equations. The acute criterion is the lesser of the following calculation results. Round the result to two significant digits.

or

b. Acute criteria: freshwater mussels absent and trout absent. To calculate total ammonia nitrogen acute criteria values (in mg N/L) in freshwater where freshwater mussels are absent and trout are absent, use the following equation. Round the result to two significant digits.

Where MIN = 51.93 or 62.15 X 10^{0.036 X (20 – T)}, whichever is less

T = Temperature in ^oC

c. Chronic criteria: freshwater mussels absent and early life stages of fish present. The chronic criteria for total ammonia nitrogen (in mg N/L) where freshwater mussels are absent (procedures for making this determination are in subdivisions 1 through 5 of this subsection) in freshwater shall not exceed concentration values calculated using the following equation. Round the result to two significant digits.

Where MIN = 6.920 or 7.547 X 10^{0.028 x (20 – T)} whichever is less

T = temperature in °C

d. Chronic criteria: freshwater mussels absent and early life stages of fish absent. The chronic criteria for total ammonia nitrogen (in mg N/L) where freshwater mussels are absent and early life stages of fish are absent (procedures for making this determination are in subdivisions 1 through 5 of this subsection) in freshwater shall not exceed concentration values calculated using the following equation. Round the result to two significant digits.

Where MAX = 7 or temperature in degrees Celsius, whichever is greater

T = temperature in °C

E. The one-hour average concentration of total ammonia nitrogen (in mg N/L) in saltwater shall not exceed, more than once every three years on the average, the acute criteria in the following table:

To calculate total ammonia nitrogen acute criteria values in saltwater at different pH and temperature values than those listed in this subsection, use the following formulas:

Where I = molal ionic strength of water

S = Salinity ppt (g/kg)

The regression model used to relate I to pKa (negative log of the ionization constant) is

pKa = 9.245 + 0.138(I)

pKa as defined by these equations is at 298 degrees Kelvin (25°C).

T °Kelvin = °C + 273

To correct for other temperatures:

pKa^S_T = pKa^S₂₉₈ + 0.0324(298 - T °Kelvin)

The unionized ammonia fraction (UIA) is given by:

The acute ammonia criterion in saltwater is given by:

Multiply the acute value by 0.822 to get the ammonia-N acute criterion.

F. The 30-day average concentration of total ammonia nitrogen (in mg N/L) in saltwater shall not exceed, more than once every three years on the average, the chronic criteria in the following table: