1. 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.
2. 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.

3. 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:

   	Appalachian monkeyface pearly mussel	Quadrula sparsa
   	Birdwing pearly mussel	Conradilla caelata
   	Cumberland monkeyface pearly mussel	Quadrula intermedia
   	Dromedary pearly mussel	Dromus dromas
   	Fine-rayed pigtoe pearly mussel	Fusconaia cuneolus
   	Shiny pigtoe pearly mussel	Fusconaia edgariana

   Threatened Species:

   	Slender chub	Hybopsis cahni
   	Yellowfin madtom	Noturus flavipinnis

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

   Endangered Species:

   	Appalachian monkeyface pearly mussel	Quadrula sparsa
   	Birdwing pearly mussel	Conradilla caelata
   	Fine-rayed pigtoe pearly mussel	Fusconaia cuneolus
   	Green blossom pearly mussel	Dysnomia torulosa gubernaculum
   	Pink mucket pearly mussel	Lampsilis orbiculata
   	Shiny pigtoe pearly mussel	Fusconaia edgariana

   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:

   Slender chub

   Hybopsis cahni

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

   Endangered Species:

   	Fine-rayed pigtoe pearly mussel	Fusconaia cuneolus
   	Shiny pigtoe pearly mussel	Fusconaia edgariana

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

   Threatened Species:

   Yellowfin madtom

   Noturus flavipinnis

   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:

   Shiny pigtoe pearly mussel

   Fusconaia edgariana

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

   Threatened Species:

   Spotfin chub

   Hybopsis monacha

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

   Endangered Species:

   Tan riffle shell mussel

   Dysnomia walkeri

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

   Threatened Species:

   Spotfin chub

   Hybopsis monacha

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.