To calculate freshwater aquatic life criteria for total recoverable metals, the equations described in (a) and (b), below, shall be used in conjunction with the coefficients shown in (c), Table 1703-3, below, provided that the values used for hardness in the equations shall be as specified in Env-Wq 1703.23(d):

1. (a) To calculate the acute criteria, in μg/L, for the metals shown Table 1703-3, the exponent “e” shall be raised to the power “x” where “x” is equal to the parenthetical expression “ma” multiplied by the natural logarithm (ln) of the hardness and to which product the value “ba” shall be added, as follows:

   Acute Criteria = e^x where x = ( m_a [ ln (hardness) ] + b_a)

2. (b) To calculate the chronic criteria, in μg/L, for the metals shown in Table 1703-3, the exponent “e” shall be raised to the power “x” where “x” is equal to the parenthetical expression “mc” multiplied by the natural logarithm of the hardness and to which product the value “bc” shall be added, as follows:

   Chronic Criteria = e^x where x = ( m_c [ ln (hardness) ] + b_c)

3. (c) Table 1703-3 shall be as follows:

   Table 1703-3: Coefficients in Equations for Calculating Total Recoverable Aquatic Life Criteria for Metals

   m_a

   b_a

   m_c

   b_c

   Cadmium

   0.9789

   -3.866

   0.7977

   -3.909

   Copper

   0.9422

   -1.700

   0.8545

   -1.702

   Chromium+3

   0.8190

   3.7256

   0.8190

   0.6848

   Lead

   1.273

   -1.460

   1.273

   -4.705

   Nickel

   0.8460

   2.255

   0.8460

   0.0584

   Silver

   1.72

   -6.59

   -------

   -------

   Zinc

   0.8473

   0.884

   0.8473

   0.884

Source. (See Revision Notes #1, #2, and #3 at chapter heading for Env-Wq 1700) #12042, eff 12-1-16; ss by #14203, eff 2-26-25