Assessment Comments

Assessment is based on results of IDNR ambient monthly monitoring and stream use assessment..

Basis for Assessment

Used assessment of the Class B(LR) aquatic life uses developed for the 1994 report, along with results of quarterly WQ monitoring conducted from October 1993 to June 1995 to develop an assessment of the Class B(LR) uses.   One of the eight samples collected during the Oct 93-Jun 95 period violated the Class B(LR) chronic WQ criterion for ammonia.  U.S.  EPA Section 305(b) guidelines allow one violation of an acute or chronic WQ criterion for toxics in grab samples collected over the assessment period in fully supported waters.  Thus, the violation of the ammonia criterion does not suggest that the aquatic life uses of this stream are impaired.   The assessment of support of aquatic life uses developed for the 1994 report, however, suggests that physical alterations to cause the aquatic life uses to be only partially supported.  A review of the field sheet from the October 1992 DNR stream use assessment shows (1) a moderately diverse fish community (9 species from 3 families) for streams in the Des Moines Lobe subecoregion and (2) less than a majority of the expected fish taxa (5 of 10) for streams in this subregion.   Follow-up monitoring is needed to better define the status of the aquatic communities and habitats and to detrmine the degree to which the Class B(LR) uses may be impaired.