Indiana Administrative Code › Title 327 - WATER POLLUTION CONTROL DIVISION › Article 5 - INDUSTRIAL WASTEWATER PRETREATMENT PROGRAMS AND NPDES › Rule 2 - Basic NPDES Requirements › Section 2-11.6 - Great Lakes system dischargers establishment of water quality-based effluent limitations (WQBELs)

Current through July 10, 2024
Authority: IC 13-14-8; IC 13-14-9; IC 13-15-1-2; IC
				  13-15-2-1; IC 13-18-3
Affected: IC 13-11-2; IC 13-18-4
Sec. 11.6.
(a) The
				NPDES permit shall include conditions necessary to achieve water quality
				standards established under 327 IAC 2-1.5, including narrative water quality
				criteria. The numeric water quality criteria set forth in
				327 IAC
				2-1.5-8 and
				327
				IAC 2-1.5-16 and Tier I criteria and Tier II values
				established under
				327 IAC
				2-1.5-11 through
				327
				IAC 2-1.5-16 shall not be enforceable against any
				point source discharger until translated into effluent limitations that are
				incorporated in NPDES permits in accordance with this article.
(b) TMDLs and WLAs developed under section
				11.4 of this rule shall provide the basis for numeric water quality-based
				effluent limitations (WQBELs) established in NPDES permits for point sources
				discharging to waters within the Great Lakes system. If a variance has been
				granted from a water quality criterion under
				327
				IAC 2-1.5-17 and
				327
				IAC 5-3-4.1, WQBELs for the pollutant that is the
				subject of the variance shall be calculated on the basis of the variance rather
				than the water quality criterion.
(c) The following procedure shall be used to
				calculate WQBELs using the WLAs developed under section 11.4 of this rule:
(1) This subsection assumes that effluent
				data follow a log-normal distribution. If a discharger is able to demonstrate
				that the effluent data for a pollutant does not follow a log-normal
				distribution and provides an alternate distribution that more accurately
				describes the data, this alternate distribution may be used instead of the
				procedures in this subsection.
(2)
				For the equations contained within this subsection, the following apply:
(A) Z99 = 2.326 (99th
				percentile probability basis).
(B)
				CV = coefficient of variation = ratio of the standard deviation to the mean. A
				value of six-tenths (0.6) will be used for the CV unless the discharger
				demonstrates that an alternate CV is more representative of the variability of
				the pollutant in the effluent.
(3) The first step in this procedure is to
				calculate a long term average (LTA) for each WLA determined for the pollutant
				under section 11.4 of this rule. These LTAs are calculated as follows:
(A) The LTAA
				protective of acute aquatic life effects shall be calculated as follows:
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Where:
[SIGMA]2
=
ln(CV2 + 1).
WLAA
=
WLA determined under section 11.4 of this rule using
							 the acute aquatic life criterion or value. This WLA is expressed as a one (1)
							 day maximum.
(B)
				The LTAC protective of chronic aquatic life effects
				shall be calculated as follows:
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Where:
[SIGMA]42
=
ln(CV2/4 + 1).
WLAC
=
For chloride, sulfate, total dissolved solids,
							 fluoride, and dissolved iron, the more stringent WLA determined under section
							 11.4 of this rule using the criterion for the pollutant under
							 327 IAC
							 2-1.5-8(j), if applicable, or the
							 chronic aquatic life criterion or value. For other pollutants, the WLA
							 determined under section 11.4 of this rule using the chronic aquatic life
							 criterion or value. This WLA is expressed as a four (4) day average.
(C)
				The LTAH protective of human health effects shall be
				calculated as follows:
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Where:
[SIGMA]302
=
ln(CV2/30 + 1).
WLAH
=
The most stringent WLA determined under section 11.4 of
							 this rule using a criterion or value for the protection of human health. This
							 WLA is expressed as a thirty (30) day average.
(D)
				The LTAW protective of wildlife effects shall be
				calculated as follows:
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Where:
[SIGMA]302
=
ln(CV2/30 + 1).
WLAW
=
WLA determined under section 11.4 of this rule using
							 the WC or WV. This WLA is expressed as a thirty (30) day average.
(4) Daily maximum and monthly average WQBELs
				are determined using the lowest LTA calculated in subdivision (3) as follows:
(A) The daily maximum WQBEL is calculated as
				follows:
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Where:
[SIGMA]2
=
ln(CV2 + 1).
(B)
				The monthly average WQBEL is calculated as follows:
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Where:
[SIGMA]n2
=
ln(CV2/n + 1).
z95
=
1.645 (95th percentile probability basis).
n
=
Number of samples per month. A value of ten (10) will
							 be used unless the discharger demonstrates that an alternate value is more
							 appropriate.
(C)
				The monthly average WQBEL shall not exceed the most stringent WLA developed
				under section 11.4 of this rule unless calculated using the following:
(i) A CV calculated using facility-specific
				effluent monitoring data that is representative of the variability of the
				pollutant in the effluent.
(ii) A
				value for n based on the monitoring frequency in the NPDES permit to be
				issued.