South Raccoon River IA 04-RAC-1181

Assessment Comments

Assessment is based on results of IDNR monthy ambient monitoring near Redfield in 2000 and 2001.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life are assessed as "fully supported."  Fish consumption uses are "not assessed."  The source of data for this assessment is the results of IDNR ambient monthly monitoring during the 2000-2001 biennial period at station 10250001 (formerly station 429340) located near Redfield approximately 1 mile downriver from confluence of Middle Raccoon and South Raccoon rivers.   EXPLANATION:  The Class B(WW) aquatic life uses were assessed as "fully supported."  None of the 25 samples collected during the 2000-2001 biennial period at the IDNR monthly station violated Class B(WW) water quality criteria for pH, dissolved oxygen, or ammonia-nitrogen; no violations occurred in the four samples analyzed for toxic metals or in the six samples analyzed for pesticides and other toxic organic compounds.   The sample collected on July 5, 2001, however, contained detectable levels of three toxic metals:  chromium (30 ug/l), copper (30 ug/l), and lead (30 ug/l).   None of these levels exceeds Iowa Class B(WW) criteria (although the value for lead is equal to the chronic Class B(WW) criterion).   Despite these detections, the results of monitoring at the Redfield station suggest full support of the Class B(WW) aquatic life uses.   Fish consumption uses were "not assessed" due to the lack of recent fish contaminant monitoring in this stream segment.