Assessment is based on results of IDNR/UHL ambient monthly monitoring near Colfax from 2000-02.
Basis for Assessment
SUMMARY: The Class B(LR) aquatic life uses are assessed (monitored) as fully supported" based on results of ambient chemical/physical water quality monitoring. The source of data for this assessment is the results of IDNR/UHL monthly ambient monitoring conducted from 2000 through 2002 on Indian Creek at a bridge 4.8 miles north of Colfax and 1.8 miles east of Green Castle in Jasper County (station 10500001).
EXPLANATION: Results of monitoring at the IDNR station show no violations of Class B(WW) criteria for pH or ammonia nitrogen (maximum value = 0.40 mg/l) in the 36 samples analyzed during the 2000-2002 assessment period and no violations of Class B(LR) chronic criteria for pesticides in the nine samples analyzed. One sample, however, contained a level of dissolved oxygen that violated the Class B(LR) water quality criterion. The sample collected on December 20, 2000, contained 4.9 mg/l of dissolved oxygen, thus slightly violating the Class B(LR) criterion of 5.0 mg/l. According to U.S. EPA guidelines for Section 305(b) reporting (U.S. EPA 1997b: page 3-17), however, a violation frequency for conventional parameters (including dissolved oxygen) of 10% or less does not suggest an impairment of aquatic life uses. Thus, the Class B(LR) aquatic life uses were assessed as "fully supported."