Assessment Comments

Assessment is based on results from IDNR ambient monthly monitoring in 2000 & 2001.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses are assessed as "fully supported."  The Class C (drinking water) uses are assessed as "fully supported."  Fish consumption uses are "not assessed."  This assessment is based on results of IDNR monthly ambient monitoring conducted during the 2000-2001 biennial period at the County Road J-53 bridge near Shambaugh (station 10730001 (formerly station 787044)).   EXPLANATION:  Monitoring at the IDNR station near Shambaugh showed no violations of Class B(WW) water quality criteria during the 2000-2001 biennial period for dissolved oxygen 5(minimum value = 8.4 mg/l), pH (range = 7.5 to 8.8 units), or ammonia-nitrogen (maximum value = 1.40) in the 24 samples analyzed during the 2000-2001 period.   In addition, levels of toxic metals in the four samples analyzed, and levels of pesticides in the six samples analyzed, were all below the analytical level of detection.   These results suggest "full support" of the Class B(WW) aquatic life uses.   The Class C (drinking water) uses were assessed as "fully supported."  Results of IDNR ambient monthly monitoring near Shambaugh show no violations of the nitrate MCL in the 24 samples collected during the 2000-2001 biennial period (mean=2.4 mg/l; maximum=10.0 mg/l).   In addition, compliance sampling conducted for the IDNR Water Supply Section as part of requirements of the federal Safe Drinking Water Act show no violations of the MCL for nitrate in finished water during the 2000-2001 biennial period.   In addition, all levels of atrazine were less than the MCL of 3.0 ug/l in the 24 samples collected during the 2000-2001 period (mean = 0.19 ug/l; maximum value = 1.2 ug/l).   Fish consumption uses are "not assessed" due to the lack of recent fish tissue monitoring in this river reach.   The most recent fish contaminant monitoring in this river segment was conducted in 1994 as part of the U.S.  EPA / IDNR fish tissue (RAFT) monitoring program.   These data are now considered too old (greater than five years) for characterizing current water quality conditions.