South Skunk River IA 03-SSK-927

Assessment Comments

Assessment is based on results of (1) IDNR ambient monthly monitoring near Oskaloosa and (2) EPA / DNR (RAFT).

Basis for Assessment

Changed the assessment of support of the Class B(WW) aquatic life uses from PS to FST due to lack of violations of Class B(WW) WQ criteria in two years (1994-95) of quarterly WQ monitoring conducted N of Oskaloosa.   Used results of USGS fish tissue monitoring conducted for the National Water Quality Assessment (NAWQA) program in September 1995 to develop an assessment of support of fish consumption uses.   The composite sample of whole-fish carp was analyzed for several organochlorine compounds, including chlordane, dieldrin, DDT, and PCBs.   Levels of all these contaminants were well below 1/2 the respective FDA action levels, thus suggesting full support (FS) of the fish consumption uses.   For more information on the USGS fish tissue study, see USGS Fact Sheet FS-027-97 (March 1997).   Continue to assess support of the Class C drinking water uses as FS based on lack of violations of Class C WQ criteria during quarterly monitoring north of Oskaloosa during FFY 1994 and 1995.   The assessment of support of the Class B(WW) uses was developed without the benefit of information on the status of the aquatic communities of this reach of the South Skunk River.   In addition, the assessment of support of the Class C uses was developed without information on levels of agricultural pesticides in the river.   Additional monitoring is needed to provide the information on aquatic communities and on levels of pesticides that is needed to develop more accurate assessments of support of the Class B(WW) and Class C uses.