English River IA 02-IOW-671

Assessment Comments

Assessment is based on results from the IDNR ambient monthly water quality monitoring station near Riverside.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses were assessed as "fully supporting / threatened" based upon ambient water quality monitoring data and biological monitoring results from 1999-2001.   Fish consumption uses remain "not assessed."  EXPLANATION:  The assessments of support of beneficial uses are based (1) on results of DNR monthly water quality monitoring conducted on the English River near Riverside during the 1998-1999 biennial period and (2) on results of pesticide monitoring conducted from April 1996 to August 1998 by USGS as part of the National Water Quality Assessment Program (NAWQA) (eastern Iowa river basins study unit, station 05455570).   None of the 24 samples collected during the 1998-1999 biennial period violated Class B(WW) water quality criteria for pH, dissolved oxygen, or ammonia-nitrogen; no violations occurred in the one sample analyzed for toxic metals.   Although these results suggest "full support" of the Class B(WW) uses, results of the USGS/NAWQA pesticide monitoring suggest that these uses be assessed as "fully supported / threatened."  One of 29 samples analyzed for pesticides contained chlorpyrifos above the Class B(WW) chronic criterion.   According to U.S.  EPA guidelines for Section 305(b) reporting (U.S.  EPA 1997b, page 3-18), this one violation of a toxic contaminant does not suggest an impairment of the aquatic life uses.   Based on DNR's assessment methodology for Section 305(b) reporting, this violation suggests that the Class B(WW) aquatic life uses should be assessed as "fully supported/threatened."  Support of the fish consumption uses remains "not assessed" due to the lack of recent fish contaminant monitoring in this river reach.