Assessment is based on results of IDNR ambient monthly monitoring near Colfax in 2000 & 2001.
Basis for Assessment
SUMMARY: The Class B(LR) aquatic life uses are assessed as fully supported." The source of data for this assessment is the results of IDNR monthly ambient monitoring conducted in 2000 and 2001 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 24 samples analyzed during the 2000-2001 biennial period and no violations of Class B(LR) chronic criteria for toxic metals in the four samples analyzed, or for pesticides and other toxic organic compounds in the six samples analyzed, during the biennial period. 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."