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

A. The one-hour average concentration of total ammonia nitrogen (in mg N/L) in freshwater shall not exceed, more than once every three years on the average1, the acute criteria below:

Acute Ammonia Freshwater Criteria
Total Ammonia Nitrogen (mg N/L)

pH

Trout Present

Trout Absent

6.5

32.6

48.8

6.6

31.3

46.8

6.7

29.8

44.6

6.8

28.1

42.0

6.9

26.2

39.1

7.0

24.1

36.1

7.1

22.0

32.8

7.2

19.7

29.5

7.3

17.5

26.2

7.4

15.4

23.0

7.5

13.3

19.9

7.6

11.4

17.0

7.7

9.65

14.4

7.8

8.11

12.1

7.9

6.77

10.1

8.0

5.62

8.40

8.1

4.64

6.95

8.2

3.83

5.72

8.3

3.15

4.71

8.4

2.59

3.88

8.5

2.14

3.20

8.6

1.77

2.65

8.7

1.47

2.20

8.8

1.23

1.84

8.9

1.04

1.56

9.0

0.885

1.32

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.

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

Where trout are present:

Acute Criterion Concentration (mg N/L) =

0.275

+

39.0

 

(1 + 107.204-pH)

(1 + 10pH-7.204)

 

Or where trout are absent:

Acute Criterion Concentration (mg N/L) =

0.411

+

58.4

(1 + 107.204-pH)

(1 + 10pH-7.204)

1The default design flow for calculating steady state waste load allocations for the acute ammonia criterion is the 1Q10 (see 9VAC25-260-140 B footnote 10) unless statistically valid methods are employed which demonstrate compliance with the duration and return frequency of the water quality criteria.

B. The 30-day average concentration of total ammonia nitrogen (in mg N/L) where early life stages of fish are present in freshwater shall not exceed, more than once every three years on the average2, the chronic criteria below:

Chronic Ammonia Freshwater Criteria
Early Life Stages of Fish Present
Total Ammonia Nitrogen (mg N/L)

 

Temperature (°C)

pH

0

14

16

18

20

22

24

26

28

30

6.5

6.67

6.67

6.06

5.33

4.68

4.12

3.62

3.18

2.80

2.46

6.6

6.57

6.57

5.97

5.25

4.61

4.05

3.56

3.13

2.75

2.42

6.7

6.44

6.44

5.86

5.15

4.52

3.98

3.50

3.07

2.70

2.37

6.8

6.29

6.29

5.72

5.03

4.42

3.89

3.42

3.00

2.64

2.32

6.9

6.12

6.12

5.56

4.89

4.30

3.78

3.32

2.92

2.57

2.25

7.0

5.91

5.91

5.37

4.72

4.15

3.65

3.21

2.82

2.48

2.18

7.1

5.67

5.67

5.15

4.53

3.98

3.50

3.08

2.70

2.38

2.09

7.2

5.39

5.39

4.90

4.31

3.78

3.33

2.92

2.57

2.26

1.99

7.3

5.08

5.08

4.61

4.06

3.57

3.13

2.76

2.42

2.13

1.87

7.4

4.73

4.73

4.30

3.78

3.32

2.92

2.57

2.26

1.98

1.74

7.5

4.36

4.36

3.97

3.49

3.06

2.69

2.37

2.08

1.83

1.61

7.6

3.98

3.98

3.61

3.18

2.79

2.45

2.16

1.90

1.67

1.47

7.7

3.58

3.58

3.25

2.86

2.51

2.21

1.94

1.71

1.50

1.32

7.8

3.18

3.18

2.89

2.54

2.23

1.96

1.73

1.52

1.33

1.17

7.9

2.80

2.80

2.54

2.24

1.96

1.73

1.52

1.33

1.17

1.03

8.0

2.43

2.43

2.21

1.94

1.71

1.50

1.32

1.16

1.02

0.897

8.1

2.10

2.10

1.91

1.68

1.47

1.29

1.14

1.00

0.879

0.773

8.2

1.79

1.79

1.63

1.43

1.26

1.11

0.973

0.855

0.752

0.661

8.3

1.52

1.52

1.39

1.22

1.07

0.941

0.827

0.727

0.639

0.562

8.4

1.29

1.29

1.17

1.03

0.906

0.796

0.700

0.615

0.541

0.475

8.5

1.09

1.09

0.990

0.870

0.765

0.672

0.591

0.520

0.457

0.401

8.6

0.920

0.920

0.836

0.735

0.646

0.568

0.499

0.439

0.386

0.339

8.7

0.778

0.778

0.707

0.622

0.547

0.480

0.422

0.371

0.326

0.287

8.8

0.661

0.661

0.601

0.528

0.464

0.408

0.359

0.315

0.277

0.244

8.9

0.565

0.565

0.513

0.451

0.397

0.349

0.306

0.269

0.237

0.208

9.0

0.486

0.486

0.442

0.389

0.342

0.300

0.264

0.232

0.204

0.179

To calculate total ammonia nitrogen chronic criteria values in freshwater when fish early life stages are present at different pH and temperature values than those listed in this subsection, use the following formulas:

Chronic Criteria Concentration =

(

0.0577

+

2.487

 )

x MIN

(1 + 107.688-pH)

(1 + 10pH-7.688)

Where MIN = 2.85 or 1.45 x 100.028(25-T), whichever is less.

T = temperature in °C

2The default design flow for calculating steady state waste load allocations for the chronic ammonia criterion where early life stages of fish are present is the 30Q10 (see 9VAC25-260-140 B footnote 10) unless statistically valid methods are employed which demonstrate compliance with the duration and return frequency of the water quality criteria.

C. The 30-day average concentration of total ammonia nitrogen (in mg N/L) where early life stages of fish are absent (procedures for making this determination are in subdivisions 1 through 4 of this subsection) in freshwater shall not exceed, more than once every three years on the average3, the chronic criteria below:

Chronic Ammonia Freshwater Criteria
Early Life Stages of Fish Absent
Total Ammonia Nitrogen (mg N/L)

Temperature (°C)

pH

0-7

8

9

10

11

12

13

14

15

16

6.5

10.8

10.1

9.51

8.92

8.36

7.84

7.35

6.89

6.46

6.06

6.6

10.7

9.99

9.37

8.79

8.24

7.72

7.24

6.79

6.36

5.97

6.7

10.5

9.81

9.20

8.62

8.08

7.58

7.11

6.66

6.25

5.86

6.8

10.2

9.58

8.98

8.42

7.90

7.40

6.94

6.51

6.10

5.72

6.9

9.93

9.31

8.73

8.19

7.68

7.20

6.75

6.33

5.93

5.56

7.0

9.60

9.00

8.43

7.91

7.41

6.95

6.52

6.11

5.73

5.37

7.1

9.20

8.63

8.09

7.58

7.11

6.67

6.25

5.86

5.49

5.15

7.2

8.75

8.20

7.69

7.21

6.76

6.34

5.94

5.57

5.22

4.90

7.3

8.24

7.73

7.25

6.79

6.37

5.97

5.60

5.25

4.92

4.61

7.4

7.69

7.21

6.76

6.33

5.94

5.57

5.22

4.89

4.59

4.30

7.5

7.09

6.64

6.23

5.84

5.48

5.13

4.81

4.51

4.23

3.97

7.6

6.46

6.05

5.67

5.32

4.99

4.68

4.38

4.11

3.85

3.61

7.7

5.81

5.45

5.11

4.79

4.49

4.21

3.95

3.70

3.47

3.25

7.8

5.17

4.84

4.54

4.26

3.99

3.74

3.51

3.29

3.09

2.89

7.9

4.54

4.26

3.99

3.74

3.51

3.29

3.09

2.89

2.71

2.54

8.0

3.95

3.70

3.47

3.26

3.05

2.86

2.68

2.52

2.36

2.21

8.1

3.41

3.19

2.99

2.81

2.63

2.47

2.31

2.17

2.03

1.91

8.2

2.91

2.73

2.56

2.40

2.25

2.11

1.98

1.85

1.74

1.63

8.3

2.47

2.32

2.18

2.04

1.91

1.79

1.68

1.58

1.48

1.39

8.4

2.09

1.96

1.84

1.73

1.62

1.52

1.42

1.33

1.25

1.17

8.5

1.77

1.66

1.55

1.46

1.37

1.28

1.20

1.13

1.06

0.990

8.6

1.49

1.40

1.31

1.23

1.15

1.08

1.01

0.951

0.892

0.836

8.7

1.26

1.18

1.11

1.04

0.976

0.915

0.858

0.805

0.754

0.707

8.8

1.07

1.01

0.944

0.885

0.829

0.778

0.729

0.684

0.641

0.601

8.9

0.917

0.860

0.806

0.756

0.709

0.664

0.623

0.584

0.548

0.513

9.0

0.790

0.740

0.694

0.651

0.610

0.572

0.536

0.503

0.471

0.442

At 15°C and above, the criterion for fish early life stages absent is the same as the criterion for fish early life stages present.

To calculate total ammonia nitrogen chronic criteria values in freshwater when fish early life stages are absent at different pH and temperature values than those listed in this subsection, use the following formulas:

Chronic Criteria Concentration =

(

0.0577

+

2.487

)

x 1.45(100.028(25-MAX))

(1 + 107.688-pH)

(1 + 10pH-7.688)

MAX = temperature in °C or 7, whichever is greater.

3The default design flow for calculating steady state waste load allocations for the chronic ammonia criterion where early life stages of fish are absent is the 30Q10 (see 9VAC25-260-140 B footnote 10) unless statistically valid methods are employed that demonstrate compliance with the duration and return frequency of the water quality criteria.

1. Site-specific modifications to the ambient water quality criteria for ammonia to account for the absence of 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 early life stages of fish present during most times of the year, the criteria shall be calculated assuming early life stages of fish are present using subsection B of this section unless the following demonstration that early life stages are absent is successfully completed. 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 Game and Inland Fisheries 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/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 by 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 where 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 fish early life stages 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 are absent. This list is available either upon request from the Office of Water Quality Programs at P.O. Box 1105, Richmond, Virginia 23218 or from the department website http://www.deq.virginia.gov/wqs.

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; 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 habitat.

D. 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 below:

Acute Ammonia Saltwater Criteria
Total Ammonia Nitrogen (mg N/L)
Salinity = 10 g/kg

 

Temperature °C

pH

0

5

10

15

20

25

30

35

7.00

231.9

159.8

110.1

75.88

52.31

36.08

24.91

17.21

7.20

146.4

100.9

69.54

47.95

33.08

22.84

15.79

10.93

7.40

92.45

63.73

43.94

30.32

20.94

14.48

10.03

6.97

7.60

58.40

40.28

27.80

19.20

13.28

9.21

6.40

4.47

7.80

36.92

25.48

17.61

12.19

8.45

5.88

4.11

2.89

8.00

23.37

16.15

11.18

7.76

5.40

3.78

2.66

1.89

8.20

14.81

10.26

7.13

4.97

3.48

2.46

1.75

1.27

8.40

9.42

6.54

4.57

3.20

2.27

1.62

1.18

0.87

8.60

6.01

4.20

2.95

2.09

1.50

1.09

0.81

0.62

8.80

3.86

2.72

1.93

1.39

1.02

0.76

0.58

0.46

9.00

2.51

1.79

1.29

0.95

0.71

0.55

0.44

0.36

Salinity = 20 g/kg

 

Temperature °C

pH

0

5

10

15

20

25

30

35

7.00

247.6

170.5

117.5

80.98

55.83

38.51

26.58

18.36

7.20

156.3

107.7

74.21

51.17

35.30

24.37

16.84

11.66

7.40

98.67

68.01

46.90

32.35

22.34

15.44

10.70

7.43

7.60

62.33

42.98

29.66

20.48

14.17

9.82

6.82

4.76

7.80

39.40

27.19

18.78

13.00

9.01

6.26

4.37

3.07

8.00

24.93

17.23

11.92

8.27

5.76

4.02

2.83

2.01

8.20

15.80

10.94

7.59

5.29

3.70

2.61

1.86

1.34

8.40

10.04

6.97

4.86

3.41

2.41

1.72

1.24

0.91

8.60

6.41

4.47

3.14

2.22

1.59

1.15

0.85

0.65

8.80

4.11

2.89

2.05

1.47

1.07

0.80

0.61

0.48

9.00

2.67

1.90

1.36

1.00

0.75

0.57

0.46

0.37

Salinity = 30 g/kg

 

Temperature °C

pH

0

5

10

15

20

25

30

35

7.00

264.6

182.3

125.6

86.55

59.66

41.15

28.39

19.61

7.20

167.0

115.1

79.31

54.68

37.71

26.03

17.99

12.45

7.40

105.5

72.68

50.11

34.57

23.87

16.50

11.42

7.92

7.60

66.61

45.93

31.69

21.88

15.13

10.48

7.28

5.07

7.80

42.10

29.05

20.07

13.88

9.62

6.68

4.66

3.27

8.00

26.63

18.40

12.73

8.83

6.14

4.29

3.01

2.13

8.20

16.88

11.68

8.10

5.64

3.94

2.78

1.97

1.42

8.40

10.72

7.44

5.18

3.63

2.56

1.82

1.31

0.96

8.60

6.83

4.77

3.34

2.36

1.69

1.22

0.90

0.68

8.80

4.38

3.08

2.18

1.56

1.13

0.84

0.64

0.50

9.00

2.84

2.01

1.45

1.06

0.79

0.60

0.47

0.39

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:

I =

19.9273S

(1000 - 1.005109S)

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:

pKaST = pKaS298 + 0.0324(298 - T °Kelvin)

The unionized ammonia fraction (UIA) is given by:

UIA =

1

1 + 10(pKaST-pH)

The acute ammonia criterion in saltwater is given by:

Acute =

0.233

UIA

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

E. 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 below:

Chronic Ammonia Saltwater Criteria
Total Ammonia Nitrogen (mg N/L)
Salinity = 10 g/kg

 

Temperature °C

pH

0

5

10

15

20

25

30

35

7.00

34.84

24.00

16.54

11.40

7.86

5.42

3.74

2.59

7.20

21.99

15.15

10.45

7.20

4.97

3.43

2.37

1.64

7.40

13.89

9.57

6.60

4.55

3.15

2.18

1.51

1.05

7.60

8.77

6.05

4.18

2.88

2.00

1.38

0.96

0.67

7.80

5.55

3.83

2.65

1.83

1.27

0.88

0.62

0.43

8.00

3.51

2.43

1.68

1.17

0.81

0.57

0.40

0.28

8.20

2.23

1.54

1.07

0.75

0.52

0.37

0.26

0.19

8.40

1.41

0.98

0.69

0.48

0.34

0.24

0.18

0.13

8.60

0.90

0.63

0.44

0.31

0.23

0.16

0.12

0.09

8.80

0.58

0.41

0.29

0.21

0.15

0.11

0.09

0.07

9.00

0.38

0.27

0.19

0.14

0.11

0.08

0.07

0.05

Salinity = 20 g/kg

 

 

Temperature °C

 

pH

0

5

10

15

20

25

30

35

 

7.00

37.19

25.62

17.65

12.16

8.39

5.78

3.99

2.76

 

7.20

23.47

16.17

11.15

7.69

5.30

3.66

2.53

1.75

 

7.40

14.82

10.22

7.04

4.86

3.36

2.32

1.61

1.12

 

7.60

9.36

6.46

4.46

3.08

2.13

1.47

1.02

0.71

 

7.80

5.92

4.08

2.82

1.95

1.35

0.94

0.66

0.46

 

8.00

3.74

2.59

1.79

1.24

0.86

0.60

0.43

0.30

 

8.20

2.37

1.64

1.14

0.79

0.56

0.39

0.28

0.20

 

8.40

1.51

1.05

0.73

0.51

0.36

0.26

0.19

0.14

 

8.60

0.96

0.67

0.47

0.33

0.24

0.17

0.13

0.10

 

8.80

0.62

0.43

0.31

0.22

0.16

0.12

0.09

0.07

 

9.00

0.40

0.28

0.20

0.15

0.11

0.09

0.07

0.06

 

Salinity = 30 g/kg

 

 

Temperature °C

 

pH

0

5

10

15

20

25

30

35

 

7.00

39.75

27.38

18.87

13.00

8.96

6.18

4.27

2.95

 

7.20

25.09

17.29

11.91

8.21

5.67

3.91

2.70

1.87

 

7.40

15.84

10.92

7.53

5.19

3.59

2.48

1.72

1.19

 

7.60

10.01

6.90

4.76

3.29

2.27

1.57

1.09

0.76

 

7.80

6.32

4.36

3.01

2.08

1.44

1.00

0.70

0.49

 

8.00

4.00

2.76

1.91

1.33

0.92

0.64

0.45

0.32

 

8.20

2.53

1.75

1.22

0.85

0.59

0.42

0.30

0.21

 

8.40

1.61

1.12

0.78

0.55

0.38

0.27

0.20

0.14

 

8.60

1.03

0.72

0.50

0.35

0.25

0.18

0.14

0.10

 

8.80

0.66

0.46

0.33

0.23

0.17

0.13

0.10

0.08

 

9.00

0.43

0.30

0.22

0.16

0.12

0.09

0.07

0.06

 

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

I =

19.9273S

(1000 - 1.005109S)

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:

pKaST = pKaS298 + 0.0324(298 - T °Kelvin)

The unionized ammonia fraction (UIA) is given by:

UIA =

1

1 + 10(pKaST-pH)

The chronic ammonia criterion in saltwater is given by:

Chronic =

0.035

UIA

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

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 10) unless statistically valid methods are employed which 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 10) unless statistically valid methods are employed which demonstrate compliance with the duration and return frequency of the water quality criteria.

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 19, Issue 23, eff. August 27, 2003; amended, Virginia Register Volume 20, Issue 9, eff. February 12, 2004; Volume 28, Issue 18, eff. June 6, 2012; Volume 32, Issue 26, eff. June 27, 2017.


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