Ill. Admin. Code tit. 35, § 352.423 - Calculation of Preliminary Effluent Limitation
a) The PEL is calculated in a simple mass
balance approach reflecting the dilution allowance established in Section
352.422:
WQS |
= |
[(Qe)(PEL) + (Qd)(Cd)] / [Qe + Qd] |
or
PEL |
= |
[WQS(Qe + Qd) - (Qd)(Cd)] / Qe |
where:
WQS |
= |
applicable water quality standard, criteria or value |
Qe |
= |
effluent flowrate |
Qd |
= |
allowable dilution flowrate |
Cd |
= |
background pollutant concentration in dilution water |
b)
The representative background concentration of pollutants to develop TMDLs and
WLAs calculated in the absence of a TMDL shall be established as follows:
1) "Background" represents all pollutant
loadings, specifically loadings that:
A) Flow
from upstream waters into the specified watershed, water body, or water body
segment for which a TMDL or WLA in the absence of a TMDL is being
developed.
B) Enter the specified
watershed, water body, or water body segment through atmospheric deposition,
chemical reaction, or sediment release or resuspension.
2) When determining what available data are
acceptable for use in calculating background, the Agency shall use its best
professional judgment, including consideration of the sampling location and the
reliability of the data through comparison, in part, to detection and
quantification levels. When data in more than 1 of the data sets or categories
described in susection (3) of this subsection (b) exists, best professional
judgment shall be used to select the data that most accurately reflects or
estimates background concentrations. Pollutant degradation and transport
information may be considered when using pollutant loading data to estimate a
water column concentration.
3) The
representative background concentration for a pollutant in the specified
watershed, water body, or water body segment shall be established as the
geometric mean of acceptable water column data or water column concentrations
estimated through the use of acceptable or projected pollutant loading data.
When determining the geometric mean of the data for a pollutant that includes
values both above and below the detection level, values less than the detection
level shall be assumed to be present at ½ of the detection level if the
detection level is less than the lowest water quality value for that pollutant.
If all of the acceptable data in a data set are below the detection level for a
pollutant, then all the data for the pollutant in that data set shall be
assumed to be zero. If the detection level of the available data is greater
than the lowest water quality value for the pollutant, then the background
concentration will be determined by the Agency on a case-by-case basis after
considering all representative data, including acceptable fish tissue
data.
Notes
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