Wyoming Administrative Code › Agency 020 - Environmental Quality, Dept. of › Sub-Agency 0011 - Water Quality › Chapter 1 - WYOMING SURFACE WATER QUALITY STANDARDS › Appendix F - Conversion Factors to Change Total Recoverable Metal Values to Dissolved Values and Equations For Hardness Dependent Metals

Current through July 13, 2024
(a) Conversion Factors. Aquatic life values for the following
				  metals are based on the dissolved amount of each substance. The recommended
				  aquatic life value was calculated by using previous 304(a) aquatic life values
				  expressed in terms of total recoverable metal and multiplying it by a
				  conversion factor (CF). The conversion factors provided below are necessary to
				  convert a metal value expressed as the total recoverable fraction in the water
				  column to the dissolved fraction in the water column.
The toxicity of these metals also varies with hardness and
				  the total recoverable value must be calculated based on the hardness (mg/L of
				  CaCO3) prior to multiplying by the conversion factor
				  (CF).
(i) The conversion factors for the following metals are
				  constants:
Metal
Acute
						  Value
Chronic Value
Chromium (III)
0.316
0.860
Copper
0.960
0.960
Nickel
0.998
0.997
Silver
0.85
n/a
Zinc
0.978
0.986
(ii) The conversion factors (CF) for cadmium and lead are not
				  constant but vary with hardness (mg/L of CaCO3).
				  Conversion factors can be calculated using the following equations, although
				  when an ambient hardness of less than 25 mg/L (as CaCO3)
				  is used to establish criteria for lead or cadmium, the conversion factor should
				  not exceed one(a):
(A) Cadmium Acute: CF = 1.136672 - [(ln
				  hardness)(0.041838)]
(B) Cadmium Chronic: CF = 1.101672 - [(ln
				  hardness)(0.041838)]
(C) Lead Acute and Chronic: CF = 1.46203 - [(ln
				  hardness)(0.145712)]
(b) Equations for Hardness Dependent Metals. Aquatic life
				  values at various hardness(b) concentrations can be
				  calculated using the formulas below. The formulas include the conversion
				  factors to derive dissolved metal values:
Parameter
Acute 1-Hour
						  Average Concentration (µg/L)
Chronic 4-Day Average
						  Concentration (µg/L)
Cadmium
e(1.0166[ln(hardness)] - 3.924)(CF)
e(0.7409[ln(hardness)] - 4.719)(CF)
Chromium (III)
e(0.8190[ln(hardness)] + 3.7256)(0.316)
e(0.8190[ln(hardness)] + 0.6848)(0.860)
Copper
e(0.9422[ln(hardness)] - 1.700)(0.960)
e(0.8545[ln(hardness)] - 1.702)(0.960)
Lead
e(1.273[ln(hardness)] - 1.460)(CF)
e(1.273[ln(hardness)] - 4.705)(CF)
Manganese
e(0.7693[ln(hardness)] + 4.4995)
e(0.5434[ln(hardness)] + 4.7850)
Nickel
e(0.8460[ln(hardness)] + 2.255)(0.998)
e(0.8460[ln(hardness)] + 0.0584)(0.997)
Silver
e(1.72[ln(hardness)] -
							 6.52)(0.85)(0.5)(c)
n/a
Zinc
e(0.8473[ln(hardness)] + 0.884)(0.978)
e(0.8473[ln(hardness)]+0.884)(0.986)
(a)Based on Guidance on the
				  Calculation of Hardness-Dependent Metals Criteria presented in:
U.S.
				  EPA. 2002. National Recommended Water Quality Criteria.
				  EPA-822-R-02-47
.
(b)Hardness as mg/L
				  CaCO3. Hardness values used in these equations must be
				  less than 400 mg/L. For hardness values greater than 400 mg/L, use 400.
(c)Criterion multiplied by 0.5 to be
				  comparable with other acute values derived using an averaging period. Value
				  does not need to be multiplied by 0.5 if criterion is to be used as an
				  instantaneous maximum or end of pipe value, as the original criterion was
				  derived using EPA's 1980 guidelines as a not to be exceeded instantaneous
				  maximum.