Statutes, codes, and regulations
Wyoming Administrative Code
Agency 020 - Environmental Quality, Dept. ofSubagency 0011 - Water Quality
Chapter 1 - WYOMING SURFACE WATER QUALITY STANDARDS
Appendix C - Ammonia Toxicity Criteria

Appendix C - Ammonia Toxicity Criteria

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Current through April 27, 2019
Appendix C - Ammonia Toxicity Criteria

(a) The ammonia values in the tables below are expressed in milligrams ammonia nitrogen per liter (mg N/L) and vary with temperature and/or pH, fish species or fish life stage. The ammonia criteria for pH values not represented in the tables can be calculated using the formulas in section (b) of Appendix C.

(i) pH-Dependent Values of the Acute Criterion (CMC)(1) for Ammonia

Acute Values, (mg N/L)
pH Salmonids Present Salmonids 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

(ii) Temperature and pH Dependent Values of the Chronic Criterion (CCC)(2) for Ammonia, Fish Early Life Stages Present

Temperature (oC)
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

(iii) Temperature and pH Dependent Values of the Chronic Criterion (CCC)(2) for Ammonia, Fish Early Life Stages Absent

Temperature (oC)
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 oC and above, the criterion for fish early life stages absent is the same as the criterion for fish early life stages present.

(b) For pH values not expressed in the tables above, ammonia toxicity criteria can be calculated as follows:

(i) Criterion maximum concentration (CMC) when salmonids or other sensitive cold water species are present:

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(ii) Criterion maximum concentration (CMC) when salmonids or other sensitive cold water species are absent:

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(iii) Criterion continuous concentration (CCC) when fish early life stages are present:

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(iv) Criterion continuous concentration (CCC) when fish early life stages are absent:

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(1)Criterion maximum concentration (CMC) refers to the one-hour average concentration of total ammonia nitrogen (mg N/L) not to be exceeded more than once every three (3) years. The CMC can also be referred to as the acute value.

(2)Criterion continuous concentration (CCC) refers to the 30-day average concentration of total ammonia nitrogen (mg N/L) not to be exceeded more than once every three (3) years. In addition, the highest 4-day average within the 30-day period should not exceed 2.5 times the CCC. The CCC can also be referred to as the chronic value. The CCC values are implemented on Class 2 waters with an assumption that early life stages of fish are present. This assumption can be rebutted, but only where a permittee, discharge permit applicant or affected party provides sufficient site-specific information to support a conclusion that the assumption is not appropriate for that water body.

Amended, Eff. 4/24/2018.