Parameter changes for developing TMDLs
In May 2001 Illinois EPA entered into a contract with Camp Dresser & McKee Inc. to
develop Total Maximum Daily Loads (TMDLs) for Casey Fork (NJ10), Casey Fork
(NJ14), Sevenmile Creek (NJC), and Jaycees Lake. In the 1998 Section 303(d) List,
Casey Fork (NJ10) was listed as impaired for the following parameters: manganese,
low dissolved oxygen (DO), and total dissolved solids (TDS); Casey Fork (NJ14) was
listed for manganese and low DO; Sevenmile Creek (NJC) was listed for low DO and
other habitat alterations; Jaycees Lake was listed for nitrogen, siltation, total
suspended solids (TSS), excessive algal growth, and chlorophyll-a.
Illinois EPA has since determined that at this time TMDLs will only be developed for
those parameters with numeric water quality standards. These numeric water quality
standards will serve as the target endpoints for TMDL development and provide a
greater degree of clarity and certainty about the TMDL and implementation plans. As
a result, a TMDL will not be developed for Jaycees Lake at this time, since numeric
water quality standards do not exist for any of the parameters listed as causes of
impairment. TMDL development for Sevenmile Creek will address the parameters of
low DO and manganese, for which numeric water quality standards exist.
New data assessed in 2002 showed that Casey Fork segments NJ10 and NJ14 are only
impaired for PCBs based on fish consumption use. This assessment was based on data
extrapolated from segment NJ07. Since no new data is directly available from
segments NJ10 and NJ14, Illinois EPA continued to develop TMDLs for the
parameters originally listed for each of these two segments. Numeric water quality
standards exist for manganese, DO, and TDS.
Causes of impairment not based on numeric water quality standards will be assigned
a lower priority for TMDL development. Pending the development of numeric water
quality standards for these parameters, as may be proposed by the Agency and
adopted by the Illinois Pollution Control Board, Illinois EPA will continue to work
toward improving water quality throughout the state by promoting and
administering existing programs and working toward creating new methods for
treating these potential causes of impairment.
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