Assessment Comments

Assessment is based on results of IDNR monthly ambient monitoring 4 mi N of Indianola during 1998 & 1999.

Basis for Assessment

SUMMARY:  Assessed support of the Class B(WW) aquatic life uses as "fully supported / threatened."  Fish consumption uses were not assessed.   EXPLANATION:  Results of quarterly water quality monitoring during the 1998-1999 biennial period at the DNR station located approximately 4 miles NNW of Indianola (station 200551) showed no violations of criteria to protect the Class B(WW) aquatic life uses:  no violations of Class B(WW) criteria for conventional or toxic parameters (dissolved oxygen, pH, and ammonia-nitrogen) occurred in the 8 samples collected during this monitoring period; neither of the two samples analyzed for toxic metals showed violations of Class B(WW) chronic criteria.   As noted in previous assessments, however, this portion of the Middle River has been extensively channelized and, based on a 1992 DNR stream use assessment, has been presumed to only "partially support" its aquatic life uses in past WQ assessments due to habitat alterations caused by hydromodification (channelization) (see above).   Results from the 1992 stream assessment, however, are more than five years old and are now considered too old for characterizing current water quality conditions.   Thus, the assessment for the 2000 report was based primary on results of chemical monitoring at the Indianola station, and the assessment of the Class B(WW) aquatic life uses was changed from "partially supported" to "fully supported / threatened."  Although water quality conditions appear to fully support the designated aquatic life uses, follow-up biological monitoring is needed to determine the status of the aquatic communities and habitats and to determine the degree to which the Class B(WW) uses are supported.   This assessment was based on results of quarterly monitoring.   Results from stations monitored monthly or more frequently, however, are preferred for Section 305(b) assessments in order to improve the accuracy and confidence level of the assessment.   As part of DNR's expanded water quality monitoring program, monthly monitoring at the Indianola station began in October 1999.   The fish consumption uses remained "not assessed" due to the lack of fish tissue monitoring in this river reach.