Virginia regulations · Through 2026 Regular Session (effective July 1, 2026)

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.

Table of Parameters6, 7

PARAMETER

CAS Number

USE DESIGNATION

AQUATIC LIFE

HUMAN HEALTH

FRESHWATER

SALTWATER

Public Water Supply3

All Other Surface Waters4

Acute1

Chronic2

Acute1

Chronic2

Acenapthene (µg/l)

83329

Acrolein (µg/l)

107028

3.0

400

Acrylonitrile (µg/l)

107131

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.61

Aldrin (µg/l)

309002

Known or suspected carcinogen; human health criteria at risk level 10-5.

3.0

1.3

0.0000077

Aluminum (µg/l)

7429905

Acute and chronic freshwater aluminum criteria values for a site shall be calculated using the 2018 Aluminum Criteria Calculator (Aluminum Criteria Calculator V.2.0.xlsx), or a calculator in R or other software package using the same 1985 Guidelines calculation approach and underlying model equations as in the Aluminum Criteria Calculator V.2.0.xlsx, as defined in EPA's Final Aquatic Life Ambient Water Quality Criteria for Aluminum. (EPA-822-R-18-001, 2018) Values displayed in the table are examples of criteria calculated by the model using the indicated input parameters for pH, hardness, and Dissolved Organic Carbon (DOC). Freshwater criteria expressed as total recoverable.

1,300

pH= 7.0

Total hardness (CaCO3) = 25 mg/l DOC = 5.0 mg/l

500

pH= 7.0

Total hardness (CaCO3) = 25 mg/l DOC = 5.0 mg/l

Ammonia (µg/l)

7664417

Chronic criterion is a 30-day average concentration not to be exceeded more than once every three years on the average.(see 9VAC25-260-155)

Anthracene (µg/l)

120127

300

400

Antimony (µg/l)

7440360

5.3

580

Arsenic (µg/l)5

7440382

340

150

Bacteria

(see 9VAC25-260-160 and 9VAC25-260-170)

Barium (µg/l)

7440393

2,000

Benzene (µg/l)

71432

Known or suspected carcinogen; human health criteria at risk level 10-5

5.8

160

Benzidine (µg/l)

92875

Known or suspected carcinogen; human health criteria at risk level 10-5

0.0014

0.11

Benzo (a) anthracene (µg/l)

56553

Known or suspected carcinogen; human health criteria at risk level 10-5

0.012

0.013

Benzo (b) fluoranthene (µg/l)

205992

Known or suspected carcinogen; human health criteria at risk level 10-5

0.012

0.013

Benzo (k) fluoranthene (µg/l)

207089

Known or suspected carcinogen; human health criteria at risk level 10-5

0.12

0.13

Benzo (a) pyrene (µg/l)

50328

Known or suspected carcinogen; human health criteria at risk level 10-5

0.0012

0.0013

Bis2-Chloroethyl Ether (µg/l)

111444

Known or suspected carcinogen; human health criteria at risk level 10-5

0.30

2,2'-Oxybis(1-Chloropropane) (µg/l)

108601

200

4,000

Bis2-Ethylhexyl Phthalate (µg/l)

117817

Known or suspected carcinogen; human health criteria at risk level 10-5. Synonym = Di-2-Ethylhexyl Phthalate.

3.2

3.7

Bromoform (µg/l)

75252

Known or suspected carcinogen; human health criteria at risk level 10-5.

1,200

Butyl benzyl phthalate (µg/l)

85687

1.0

Cadmium (µg/l)5

7440439

Freshwater values are a function of total hardness as calcium carbonate (CaCO3) mg/l and the WER. The minimum hardness allowed for use in the equation below shall be 25 and the maximum hardness shall be 400 even when the actual ambient hardness is less than 25 or greater than 400.

Freshwater acute criterion (µg/l)

WER e (0.9789[ln(hardness)]-3.866) (CFa)

Freshwater chronic criterion (µg/l)

WER e (0.7977[ln(hardness)]-3.909) (CFc)

WER = Water Effect Ratio = 1 unless determined otherwise under 9VAC25-260-140 F

e = natural antilogarithm

ln = natural logarithm

CF = conversion factor a (acute) or c (chronic)

CFa = 1.136672-[(ln hardness)(0.041838)]

CFc = 1.101672-[(ln hardness)(0.041838)]

1.8

CaCO3 = 100

0.72

CaCO3 = 100

X WER

7.9

X WER

Carbon tetrachloride (µg/l)

56235

Known or suspected carcinogen; human health criteria at risk level 10-5.

4.0

Carbaryl (µg/l)

63252

2.1

1.6

Chlordane (µg/l)

57749

Known or suspected carcinogen; human health criteria at risk level 10-5.

2.4

0.0043

0.09

0.0040

0.0031

0.0032

Chloride (µg/l)

16887006

Human health criterion to maintain acceptable taste and aesthetic quality and applies at the drinking water intake.

Chloride criteria do not apply in Class II transition zones (see subsection C of this section).

860,000

230,000

250,000

Chlorine, Total Residual (µg/l)

7782505

In DWR class i and ii trout waters (9VAC25-260-390 through 9VAC25-260-540) or waters with threatened or endangered species are subject to the halogen ban (9VAC25-260-110).

See 9VAC25-260-110

Chlorine Produced Oxidant (µg/l)

7782505

7.5

Chlorobenzene (µg/l)

108907

100

800

Chlorodibromomethane (µg/l)

124481

Known or suspected carcinogen; human health criteria at risk level 10-5.

8.0

210

Chloroform (µg/l)

67663

2,000

2-Chloronaphthalene (µg/l)

91587

800

1,000

2-Chlorophenol (µg/l)

95578

800

Chlorpyrifos (µg/l)

2921882

0.083

0.041

0.011

0.0056

Chromium III (µg/l)5

16065831

Freshwater values are a function of total hardness as calcium carbonate CaCO3 mg/l and the WER. The minimum hardness allowed for use in the equation below shall be 25 and the maximum hardness shall be 400 even when the actual ambient hardness is less than 25 or greater than 400.

Freshwater acute criterion µg/l

WER [e{0.8190[ln(hardness)]+3.7256}] (CFa)

Freshwater chronic criterion µg/l

WER [e{0.8190[ln(hardness)]+0.6848}] (CFc)

WER = Water Effect Ratio = 1 unless determined otherwise under 9VAC25-260-140.F

e = natural antilogarithm

ln = natural logarithm

CF = conversion factor a (acute) or c (chronic)

CFa= 0.316

CFc=0.860

570

(CaCO3 = 100)

100

(total Cr)

Chromium VI (µg/l)5

18540299

1,100

Chrysene (µg/l)

218019

Known or suspected carcinogen; human health criteria at risk level 10-5.

1.2

1.3

Copper (µg/l)5

7440508

Freshwater acute criterion (µg/l)

WER [e {0.9422[ln(hardness)]-1.700}] (CFa)

Freshwater chronic criterion (µg/l)

WER [e {0.8545[ln(hardness)]-1.702}] (CFc)

WER = Water Effect Ratio = 1 unless determined otherwise under 9VAC25-260-140 F.

e = natural antilogarithm

ln = natural logarithm

CF = conversion factor a (acute) or c (chronic)

CFa = 0.960

CFc = 0.960

Alternate copper criteria in freshwater: the freshwater criteria for copper can also be calculated using the EPA 2007 Biotic Ligand Model (See 9VAC25-260-140 G).

Acute saltwater criterion is a 24-hour average not to be exceeded more than once every three years on the average.

CaCO 3 = 100

9.0

CaCO3 = 100

9.3

X WER

6.0

X WER

1,300

Cyanide, Free (µg/l)

57125

5.2

1.0

400

DDD (µg/l)

72548

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.0012

DDE (µg/l)

72559

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.00018

DDT (µg/l)

50293

Known or suspected carcinogen; human health criteria at risk level 10-5.

Total concentration of DDT and metabolites shall not exceed aquatic life criteria.

1.1

0.0010

0.13

0.0010

0.00030

Demeton (µg/l)

8065483

0.1

Diazinon (µg/l)

333415

0.17

0.82

Dibenz (a, h) anthracene (µg/l)

53703

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.0012

0.0013

1,2-Dichlorobenzene (µg/l)

95501

1,000

3,000

1,3-Dichlorobenzene (µg/l)

541731

1,4 Dichlorobenzene (µg/l)

106467

300

900

3,3 Dichlorobenzidine (µg/l)

91941

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.49

1.5

Dichlorobromomethane (µg/l)

75274

Known or suspected carcinogen; human health criteria at risk level 10-5.

9.5

270

1,2 Dichloroethane (µg/l)

107062

Known or suspected carcinogen; human health criteria at risk level 10-5.

6,500

1,1 Dichloroethylene (µg/l)

75354

300

20,000

1,2-trans-dichloroethylene (µg/l)

156605

100

4,000

2,4 Dichlorophenol (µg/l)

120832

2,4 Dichlorophenoxy acetic acid (Chlorophenoxy Herbicide) (2,4-D) (µg/l)

94757

1,300

12,000

1,2-Dichloropropane (µg/l)

78875

Known or suspected carcinogen; human health criteria at risk level 10-5.

9.0

310

1,3-Dichloropropene (µg/l)

542756

Known or suspected carcinogen; human health criteria at risk level 10-5.

2.7

120

Dieldrin (µg/l)

60571

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.24

0.056

0.71

0.0019

0.000012

Diethyl Phthalate (µg/l)

84662

600

2,4 Dimethylphenol (µg/l)

105679

100

3,000

Dimethyl Phthalate (µg/l)

131113

2,000

Di-n-Butyl Phthalate (µg/l)

84742

2,4 Dinitrophenol (µg/l)

51285

300

Dinitrophenols (µg/l)

25550587

1,000

2-Methyl-4,6-Dinitrophenol (µg/l)

534521

2,4 Dinitrotoluene (µg/l)

121142

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.49

Dioxin 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (µg/l)

1746016

4.6 E-8

4.7 E-8

1,2-Diphenylhydrazine (µg/l)

122667

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.3

2.0

Dissolved Oxygen (µg/l)

(See 9VAC25-260-50)

Alpha-Endosulfan (µg/l)

959988

Total concentration alpha and beta-endosulfan shall not exceed aquatic life criteria.

0.22

0.056

0.034

0.0087

Beta-Endosulfan (µg/l)

33213659

Total concentration alpha and beta-endosulfan shall not exceed aquatic life criteria.

0.22

0.056

0.034

0.0087

Endosulfan Sulfate (µg/l)

1031078

Endrin (µg/l)

72208

0.086

0.036

0.037

0.0023

0.03

Endrin Aldehyde (µg/l)

7421934

Ethylbenzene (µg/l)

100414

130

Fecal Coliform

(see 9VAC25-260-160)

Fluoranthene (µg/l)

206440

Fluorene (µg/l)

86737

Foaming Agents (µg/l)

Criterion measured as methylene blue active substances. Criterion to maintain acceptable taste, odor, or aesthetic quality of drinking water and applies at the drinking water intake.

500

Guthion (µg/l)

86500

0.01

Heptachlor (µg/l)

76448

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.52

0.0038

0.053

0.0036

0.000059

Heptachlor Epoxide (µg/l)

1024573

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.52

0.0038

0.053

0.0036

0.00032

Hexachlorobenzene (µg/l)

118741

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.00079

Hexachlorobutadiene (µg/l)

87683

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.1

Hexachlorocyclohexane Alpha-BHC (µg/l)

319846

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.0036

0.0039

Hexachlorocyclohexane Beta-BHC (µg/l)

319857

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.080

0.14

Hexachlorocyclohexane (µg/l) (Lindane)

Gamma-BHC

58899

0.95

0.16

4.2

4.4

Hexachlorocyclohexane (HCH)-Technical (µg/l)

608731

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.066

0.1

Hexachlorocyclopentadiene (µg/l)

77474

Hexachloroethane (µg/l)

67721

Known or suspected carcinogen; human health criteria at risk level 10-5.

Hydrogen sulfide (µg/l)

7783064

2.0

Indeno (1,2,3,-cd) pyrene (µg/l)

193395

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.012

0.013

Iron (µg/l)

7439896

Criterion to maintain acceptable taste, odor, or aesthetic quality of drinking water and applies at the drinking water intake.

300

Isophorone (µg/l)

78591

Known or suspected carcinogen; human health criteria at risk level 10-5.

340

18,000

Kepone (µg/l)

143500

zero

Lead (µg/l)5

7439921

Freshwater values are a function of total hardness as calcium carbonate CaCO3 mg/l and the water effect ratio. The minimum hardness allowed for use in the equation below shall be 25 and the maximum hardness shall be 400 even when the actual ambient hardness is less than 25 or greater than 400.

Freshwater acute criterion (µg/l)

WER [e {1.273[ln(hardness)]-1.084}](CFa)

Freshwater chronic criterion (µg/l)

WER [e {1.273[ln(hardness)]-3.259}] (CFc)

WER = Water Effect Ratio = 1 unless determined otherwise under 9VAC25-260-140 F

e = natural antilogarithm

ln = natural logarithm

CF = conversion factor a (acute) or c (chronic)

CFa = 1.46203-[(ln hardness)(0.145712)]

CFc = 1.46203-[(ln hardness)(0.145712)]

CaCO3 = 100

230 X WER

8.8 X WER

Malathion (µg/l)

121755

0.1

Mercury (µg/l) 5

7439976

1.4

0.77

1.8

0.94

Methyl Bromide (µg/l)

74839

100

10,000

3-Methyl-4-Chlorophenol

59507

500

2,000

Methyl Mercury (Fish Tissue Criterion mg/kg) 8

22967926

0.30

Methylene Chloride (µg/l)

75092

Known or suspected carcinogen; human health criteria at risk level 10-5. Synonym = Dichloromethane

1,000

Methoxychlor (µg/l)

72435

0.03

0.02

Mirex (µg/l)

2385855

zero

Nickel (µg/l)5

7440020

Freshwater acute criterion (µg/l)

WER [e {0.8460[ln(hardness)] + 1.312}] (CFa)

Freshwater chronic criterion (µg/l)

WER [e {0.8460[ln(hardness)] - 0.8840}] (CFc)

WER = Water Effect Ratio = 1 unless determined otherwise under 9VAC25-260-140 F

e = natural antilogarithm

ln = natural logarithm

CF = conversion factor a (acute) or c (chronic)

CFa = 0.998

CFc = 0.997

180

CaCO3 = 100

74 X WER

8.2 X WER

470

1,500

Nitrate as N (µg/l)

14797558

10,000

Nitrobenzene (µg/l)

98953

600

N-Nitrosodimethylamine (µg/l)

62759

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.0065

N-Nitrosodiphenylamine (µg/l)

86306

Known or suspected carcinogen; human health criteria at risk level 10-5.

N-Nitrosodi-n-propylamine (µg/l)

621647

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.047

4.6

Nonylphenol (µg/l)

84852153

6.6

7.0

1.7

Parathion (µg/l)

56382

0.065

0.013

PCB Total (µg/l)

1336363

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.014

0.030

0.00058

Pentachlorobenzene (µg/l)

608935

0.1

Pentachlorophenol (µg/l)

87865

Known or suspected carcinogen; human health criteria risk level at 10-5.

Freshwater acute criterion (µg/l)

e (1.005(pH)-4.869)

Freshwater chronic criterion (µg/l)

e (1.005(pH)-5.134)

8.7

pH = 7.0

6.7

pH = 7.0

7.9

0.3

0.4

See 9VAC25-260-50

Phenol (µg/l)

108952

4,000

300,000

Phosphorus Elemental (µg/l)

7723140

0.10

Pyrene (µg/l)

129000

Radionuclides

Gross Alpha Particle Activity (pCi/L)

Beta Particle & Photon Activity (mrem/yr) (formerly man-made radionuclides)

Combined Radium 226 and 228 (pCi/L)

Uranium (µg/L)

7440611

Selenium (µg/l)5

7782492

WER shall not be used for freshwater acute and chronic criteria. Freshwater criteria expressed as total recoverable.

5.0

290 X WER

X WER

160

3,800

Silver (µg/l)5

7440224

Freshwater acute criterion (µg/l)

WER [e {1.72[ln(hardness)]-6.52}] (CFa)

WER = Water Effect Ratio = 1 unless determined otherwise under 9VAC25-260-140 F

e = natural antilogarithm

ln = natural logarithm

CF = conversion factor a

(acute) or c (chronic)

CFa = 0.85

3.4; CaCO3 = 100

1.9 X WER

Sulfate (µg/l)

Criterion to maintain acceptable taste, odor, or aesthetic quality of drinking water and applies at the drinking water intake.

250,000

Temperature

See 9VAC25-260-50

1,2,4,5-Tetrachlorobenzene

95943

0.03

1,1,2,2-Tetrachloroethane (µg/l)

79345

Known or suspected carcinogen; human health criteria at risk level 10-5.

2.0

Tetrachloroethylene (µg/l)

127184

Known or suspected carcinogen; human health criteria at risk level 10-5.

100

290

Thallium (µg/l)

7440280

0.22

0.43

Toluene (µg/l)

108883

520

Total Dissolved Solids (µg/l)

Criterion to maintain acceptable taste, odor or aesthetic quality of drinking water and applies at the drinking water intake.

500,000

Toxaphene (µg/l)

8001352

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.73

0.0002

0.21

0.0002

0.0070

0.0071

Tributyltin (µg/l)

E1790678

0.46

0.072

0.42

0.0074

1, 2, 4 Trichlorobenzene (µg/l)

120821

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.71

0.76

1,1,1-Trichloroethane

71556

10,000

200,000

1,1,2-Trichloroethane (µg/l)

79005

Known or suspected carcinogen; human health criteria at risk level 10-5.

5.5

Trichloroethylene (µg/l)

79016

Known or suspected carcinogen; human health criteria at risk level 10-5.

6.0

2, 4, 5 –Trichlorophenol

95954

300

600

2, 4, 6-Trichlorophenol (µg/l)

88062

Known or suspected carcinogen; human health criteria at risk level 10-5.

2-(2, 4, 5-Trichlorophenoxy) propionic acid (Silvex) (µg/l)

93721

100

400

Vinyl Chloride (µg/l)

75014

Known or suspected carcinogen; human health criteria at risk level 10-5.

0.22

Zinc (µg/l)5

7440666

Freshwater values are a function of total hardness as calcium carbonate (CaCO3) mg/l and the WER. The minimum hardness allowed for use in the equation below shall be 25 and the maximum, hardness shall be 400 even when the actual ambient hardness is less than 25 or greater than 400.

Freshwater acute criterion (µg/l)

WER [e {0.8473[ln(hardness)]+0.884}](CFa)

Freshwater chronic criterion (µg/l)

WER [e{0.8473[ln(hardness)]+0.884}] (CFc)

WER = Water Effect Ratio = 1 unless determined otherwise under 9VAC25-260-140 F

e = natural antilogarithm

ln = natural logarithm

CF = conversion factor a (acute) or c (chronic)

CFa = 0.978

CFc = 0.986

120 CaCO3 = 100

X WER

7,000

23,000

1One hour average concentration not to be exceeded more than once every 3 years on the average, unless otherwise noted.

2Four-day average concentration not to be exceeded more than once every 3 years on the average, unless otherwise noted.

3Criteria have been calculated to protect human health from toxic effects through drinking water and fish consumption, unless otherwise noted and apply in segments designated as PWS in 9VAC25-260-390 through 9VAC25-260-540. Human health criteria are based on the assumption of average amount of exposure on a long-term basis.

4Criteria have been calculated to protect human health from toxic effects through fish consumption, unless otherwise noted and apply in all other surface waters not designated as PWS in 9VAC25-260-390 through 9VAC25-260-540. Human health criteria are based on the assumption of average amount of exposure on a long-term basis.

5Acute and chronic saltwater and freshwater aquatic life criteria apply to the biologically available form of the metal and apply as a function of the pollutant's water effect ratio (WER) as defined in 9VAC25-260-140 F (WER X criterion). Metals measured as dissolved shall be considered to be biologically available, or, because local receiving water characteristics may otherwise affect the biological availability of the metal, the biologically available equivalent measurement of the metal can be further defined by determining a water effect ratio (WER) and multiplying the numerical value shown in 9VAC25-260-140 B by the WER. Refer to 9VAC25-260-140 F. Values displayed above in the table are examples and correspond to a WER of 1.0. Metals criteria have been adjusted to convert the total recoverable fraction to dissolved fraction using a conversion factor. Criteria that change with hardness have the conversion factor listed in the table above.

6The flows listed below are default design flows for calculating steady state wasteload allocations unless statistically valid methods are employed which demonstrate compliance with the duration and return frequency of the water quality criteria.

Aquatic Life:

Acute criteria

1Q10

Chronic criteria

7Q10

Chronic criteria (ammonia)

30Q10

Human Health:

Noncarcinogens

30Q5

Carcinogens

Harmonic mean

The following are defined for this section:

"1Q10" means the lowest flow averaged over a period of 1 day which on a statistical basis can be expected to occur once every 10 climatic years.

"7Q10" means the lowest flow averaged over a period of 7 consecutive days that can be statistically expected to occur once every 10 climatic years.

"30Q5" means the lowest flow averaged over a period of 30 consecutive days that can be statistically expected to occur once every 5 climatic years.

"30Q10" means the lowest flow averaged over a period of 30 consecutive days that can be statistically expected to occur once every 10 climatic years.

"Averaged" means an arithmetic mean.

"Climatic year" means a year beginning on April 1 and ending on March 31.

7The criteria listed in this table are two significant digits. For other criteria that are referenced to other sections of this regulation in this table, all numbers listed as criteria values are significant.

8The fish tissue criterion for methylmercury applies to a concentration of 0.30 mg/kg as wet weight in edible tissue for species of fish and shellfish resident in a waterbody that are commonly eaten in the area and have commercial, recreational, or subsistence value.

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:

CLASS OF WATERS

NUMERICAL CRITERIA

I and II (Estuarine Waters)

Saltwater criteria apply

II (Transition Zone)

More stringent of either the freshwater or saltwater criteria apply

II (Tidal Freshwater), III, IV, V, VI and VII

Freshwater criteria apply

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.

Where this section sits in the code

Title 9. Environment
Agency 25. State Water Control Board
Chapter 260. Water Quality Standards
Part I. Surface Water Standards with General, Statewide Application