Assessment Comments

Assessment is based on results of IDNR ambient monthly water quality monitoring near Missouri Valley in 2000 & 2001.

Basis for Assessment

[Note:  For the 2002 report, the previous waterbody segment for the Boyer River (IA 06-BOY-0020-0), which extended 46 miles from Willow Creek in Harrison County to East Boyer R.  in Crawford County, was split into two subsegments:  (1) Willow Creek to the Harrison/Crawford county line (IA 06-BOY-0020-1) and (2) Harrison/Crawford county line to East Boyer River near Denison (IA 06-BOY-0020-2).   See previous Section 305(b) assessments from this subsegment (IA 06-BOY-0020-1) for assessments of the original 46-mile stream segment.]

SUMMARY:  The Class B(WW) aquatic life uses are assessed as "fully supported."  Fish consumption uses remain "not assessed."  This assessment is based on results of IDNR monthly ambient monitoring conducted during the 2000-2001 biennial period at the County Road F-58 bridge NE of Missouri Valley (station 10430001 (formerly station 822304)).   EXPLANATION:  Monitoring at the IDNR station near Missouri Valley showed no violations of Class B(WW) water quality criteria for dissolved oxygen (minimum value = 6.7 mg/l), pH (range = 7.7 to 8.4), or ammonia nitrogen (maximum value = 2.0 mg/l) in the 24 samples analyzed during the 2000-2001 period.   The maximum value of ammonia-nitrogen (2.0 mg/l) occurred in the sample collected on March 5, 2001; this level did not exceed the Class B(WW) criterion.   The next highest level of ammonia nitrogen was 0.5 mg/l on April 17, 2000.   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.   Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this river segment.