Assessment is based on results of IDNR monthy ambient water quality monitoring near Redfield from 2000-02.
Basis for Assessment
SUMMARY: The Class B(WW) aquatic life are assessed (monitored) as "fully supported / threatened" due to a single violation of state criteria for ammonia. Fish consumption uses are "not assessed" due to the lack of fish contaminant monitoring in this river segment. The source of data for this assessment is the results of IDNR/UHL ambient monthly monitoring during the 2000-2002 assessment period at STORET station 10250001 (formerly station 429340) located near Redfield approximately 1 mile downriver from the confluence of Middle Raccoon and South Raccoon rivers.
EXPLANATION: The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported / threatened" based on results of IDNR/UHL ambient water quality monitoring. None of the 37 samples collected during the 2000-2002 assessment period at the IDNR monthly station violated Class B(WW) water quality criteria for pH or dissolved oxygen; no violations occurred in the nine samples analyzed for pesticides and other toxic organic compounds. The Class B(WW) aquatic life uses are assessed (monitored) as "fully supported / threatened" based on results of ambient chemical/physical water quality monitoring that showed a single violation of state criteria for ammonia-nitrogen. The sample collected on April 3, 2002 contained 1.4 mg/l of ammonia, thus violating state criteria. According to U.S. EPA guidelines for Section 305(b) reporting (U.S. EPA 1997b, page 3-18), this single violation of chronic criteria for ammonia does not suggest an impairment of aquatic life uses. Based on DNR's assessment methodology for Section 305(b) reporting, however, this violation does suggest that the Class B(WW) aquatic life uses should be assessed as "fully supported/threatened." In addition, the sample collected on July 5, 2001 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).
Fish consumption uses were "not assessed" due to the lack of recent fish contaminant monitoring in this stream segment.