Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 260 - WATER QUALITY STANDARDS › Part I - Surface Water Standards with General, Statewide Application › Section 9VAC25-260-140 - Criteria for surface water

Current through Register Vol. 40, No. 24, July 15, 2024
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
70
90
Acrolein (µg/l)
107028
3.0
3.0
3
400
Acrylonitrile (µg/l)
107131
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
0.61
70
Aldrin (µg/l)
309002
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
3.0
1.3
0.0000077
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
69
36
10
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
22
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.
70
1,200
Butyl benzyl phthalate (µg/l)
85687
1.0
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)]
1.8CaCO3 = 100
0.72CaCO3 = 100
33X WER
7.9X WER
5
Carbon tetrachloride (µg/l)
56235
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
4.0
50
Carbaryl (µg/l)
63252
2.1
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).
19
See
								9VAC25-260-110
11
See
								9VAC25-260-110
Chlorine Produced Oxidant (µg/l)
7782505
13
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
60
2,000
2-Chloronaphthalene (µg/l)
91587
800
1,000
2-Chlorophenol (µg/l)
95578
30
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)
74(CaCO3 = 100)
100
(total Cr)
Chromium VI
								(µg/l)5
18540299
16
11
1,100
50
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 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
								  {0.9422[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.
13CaCO 3 = 100
9.0CaCO3 = 100
9.3X WER
6.0X WER
1,300
Cyanide, Free (µg/l)
57125
22
5.2
1.0
1.0
4
400
DDD (µg/l)
72548
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
0.0012
0.0012
DDE (µg/l)
72559
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
0.00018
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
0.00030
Demeton (µg/l)
8065483
0.1
0.1
Diazinon (µg/l)
333415
0.17
0.17
0.82
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
7
10
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.
99
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
10
60
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
0.000012
Diethyl Phthalate (µg/l)
84662
600
600
2,4 Dimethylphenol (µg/l)
105679
100
3,000
Dimethyl Phthalate (µg/l)
131113
2,000
2,000
Di-n-Butyl Phthalate (µg/l)
84742
20
30
2,4 Dinitrophenol (µg/l)
51285
10
300
Dinitrophenols (µg/l)
25550587
10
1,000
2-Methyl-4,6-Dinitrophenol (µg/l)
534521
2
30
2,4 Dinitrotoluene (µg/l)
121142
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
0.49
17
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
20
30
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
20
40
Endosulfan Sulfate (µg/l)
1031078
20
40
Endrin (µg/l)
72208
0.086
0.036
0.037
0.0023
0.03
0.03
Endrin Aldehyde (µg/l)
7421934
1
1
Ethylbenzene (µg/l)
100414
68
130
Fecal Coliform
(see
								9VAC25-260-160)
Fluoranthene (µg/l)
206440
20
20
Fluorene (µg/l)
86737
50
70
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
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
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
0.00032
Hexachlorobenzene (µg/l)
118741
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
0.00079
0.00079
Hexachlorobutadiene (µg/l)
87683
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
0.1
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
4
4
Hexachloroethane (µg/l)
67721
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
1
1
Hydrogen sulfide (µg/l)
7783064
2.0
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
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)]
94 CaCO3 = 100
11 CaCO3 = 100
230 X WER
8.8 X WER
15
Malathion (µg/l)
121755
0.1
0.1
Mercury (µg/l)
57439976
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
0.30
Methylene Chloride (µg/l)
75092
Known or suspected carcinogen; human health
								criteria at risk level 10-5.Synonym =
								Dichloromethane
20
1,000
Methoxychlor (µg/l)
72435
0.03
0.03
0.02
0.02
Mirex (µg/l)
2385855
zero
zero
Nickel
								(µg/l)5
7440020
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 
								{0.8460[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
180CaCO3 = 100
20CaCO3 = 100
74 X WER
8.2 X WER
470
1,500
Nitrate as N (µg/l)
14797558
10,000
Nitrobenzene (µg/l)
98953
10
600
N-Nitrosodimethylamine (µg/l)
62759
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
0.0065
27
N-Nitrosodiphenylamine (µg/l)
86306
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
30
55
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
28
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
0.00058
Pentachlorobenzene (µg/l)
608935
0.1
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
6.7pH = 7.0
13
7.9
0.3
0.4
pH
See
								9VAC25-260-50
Phenol (µg/l)
108952
4,000
300,000
Phosphorus Elemental (µg/l)
7723140
0.10
Pyrene (µg/l)
129000
20
30
Radionuclides
Gross Alpha Particle Activity (pCi/L)
15
Beta Particle & Photon Activity (mrem/yr)
								(formerly man-made radionuclides)
4
Combined Radium 226 and 228 (pCi/L)
5
Uranium (µg/L)
7440611
30
Selenium
								(µg/l)5
7782492
WER shall not be used for freshwater acute and
								chronic criteria. Freshwater criteria expressed as total recoverable.
20
5.0
290 X WER
71 X WER
160
3,800
Silver
								(µg/l)5
7440224
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
								  {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
0.03
1,1,2,2-Tetrachloroethane (µg/l)
79345
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
2.0
30
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
57
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-Trichloroethane71556
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
89
Trichloroethylene (µg/l)
79016
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
6.0
70
2, 4, 5 -Trichlorophenol95954
300
600
2, 4, 6-Trichlorophenol (µg/l)
88062
Known or suspected carcinogen; human health
								criteria at risk level 10-5.
15
28
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
16
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
120 CaCO3 = 100
90 X WER
81X 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.