Assessment is based on results of (1) DNR monthly ambient station NE of Conesville and (2) USGS NAWQA monitoring of water quality and fish tissue near Conesville.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses remain assessed as fully supported. The Class B(WW) aquatic life were assessed as "fully supported / threatened." Fish consumption uses remain assessed as fully supported / threatened. EXPLANATION: Results of DNR quarterly WQ monitoring in 1996 and 1997 from the DNR station located near Conesville (station 323015) showed relatively low levels of indicator bacteria (fecal coliforms) in samples collected during summers of 1996 and 1997. Based on this information, the Class A uses were assessed as fully supported (see assessment for the 1998 report above). Results of this monitoring also showed no violations of WQ criteria to protect the Class B(WW) aquatic life uses: no violations of state water quality criteria conventional or toxic parameters (dissolved oxygen, pH, and ammonia-nitrogen) occurred in the 8 samples collected during this monitoring period; neither of the two samples analyzed for toxic metals showed violations of these criteria. Results of monitoring by USGS at this station from March 1996 to October 1996 as part of the eastern Iowa basins NAWQA project (station 05465000) were consistent with results of DNR monitoring. This monitoring, however, showed that one of nine samples contained a level of dieldrin above the chronic water quality criterion to protect the Class B(WW) aquatic life uses. According to U.S. EPA guidelines for Section 305(b) reporting (U.S. EPA 1997b, page 3-18), this one violation 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." This assessment was based on results of quarterly monitoring. Results from stations monitored monthly or more frequently, however, are preferred for Section 305(b) assessments in order to improve the accuracy and confidence level of the assessement. As part of DNR's expanded water quality monitoring program, monthly monitoring at the Conesville station began in October 1999. Fish consumption uses remain assessed as "fully supported/threatened" based on results of USGS monitoring in September 1995 that showed levels of dieldrin in the sample of whole-fish carp were above ½ of the FDA action level (see assessment for the 1998 report).