Assessment Comments

Assessment is based on results of (1) IDNR/UHL ambient monthly monitoring from 2002-04 and (2) IDNR/UHL biological (biocriteria) sampling in 2004.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses are assessed (evaluated) as "partially supported" based on results of biological monitoring in 2004.   Fish consumption uses remain assessed "not assessed" due to the lack of fish contaminant monitoring in this river reach.   This assessment is based on (1) results of IDNR/UHL monthly ambient water quality monitoring conducted during the 2002-2004 assessment period at the State Highway 2 bridge 2 miles east of Clarinda (STORET station 10730002 (formerly station 780809)) and (2) results of IDNR/UHL biocriteria monitoring in 2004.   The assessment is considered evaluated because during the field fish collection, staff encountered equipment failure and combined with the width and depth of the stream, the results are unreliable.   The aquatic life uses are considered "partially supporting" because the FIBI score (23 + UAV (7)) failed to meet the FIBI BIC (31).   This site will be assessed again in the near future.    

EXPLANATION:  Results of monitoring at the IDNR/UHL ambient monitoring station east of Clarinda showed no violations of Class B(WW) water quality criteria during the 2002-2004 assessment period for dissolved oxygen (minimum value = 5.7 mg/l), pH (range = 7.6 to 8.6 units), or ammonia-nitrogen (maximum value = 0.6 mg/l) in the 36 samples analyzed.   In addition, levels of pesticides in the seven samples analyzed, and levels of toxic metals in the ten samples analyzed, were all below the respective Class B(WW) criteria.   These results suggest "full support" of the Class B(WW) aquatic life uses.  

Results of biological monitoring, however, suggest that the Class B(WW) uses are only "partially supported".   Based on IDNR/UHL biocriteria monitoring in 2004, the 2004 FIBI score was 23 (poor) and the BMIBI score was 46 (fair).   This suggests the aquatic life use support be assessed (evaluated - see above) as partially supported (= PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports.  The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 31 and the BMIBI BIC for this ecoregion is 54.

Fish consumption uses remain "not assessed" due to the lack of recent fish tissue monitoring in this river reach.