Assessment Comments
Assessment is based on results of IDNR ambient city monitoring and fish tissue (RAFT) monitoring.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses were assessed as "partially supported." The Class B(WW) aquatic life uses were assessed as "fully supported." Fish consumption uses remain assessed as "fully supported." The sources of data for this assessment are (1) the results of monthly monitoring from October 1999 through September 2001 at the IDNR ambient city monitoring station located at upstream from Waterloo at the old highway 218 bridge at Cedar Falls and (2) the results of U.S. EPA/IDNR fish tissue (RAFT) monitoring at Cedar Falls in 1997. EXPLANATION: The Class A uses were assessed as "partially supported." For purposes of Section 305(b) assessments, DNR uses the long-term average monthly flow plus one standard deviation of this average to identify river flows that are materially affected by surface runoff. According to the Iowa Water Quality Standards (IAC 1990:8), the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) does not apply "when the waters are materially affected by surface runoff." Seven of the 8 samples collected from the Cedar Falls station during the 2000 and 2001 recreational seasons were collected at flows not materially affected by surface runoff. The geometric mean level of indicator bacteria (fecal coliforms) in these seven non-runoff-affected samples (109 orgs/100ml) is below the Iowa Class A water quality criterion of 200 orgs/100ml. However, one of the seven samples (14%) contained a level of fecal coliform bacteria that exceeded the U.S. EPA-recommended single-sample maximum value of 400 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting, if more than 10% of samples exceed this single-sample maximum value, the primary contact recreation uses are "partially supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Because less than 10 non-flow affected samples were available for this assessment, the assessment type is considered "evaluated"; thus, this assessment is not of sufficient quality to support a Section 303(d) listing. The Class B(WW) aquatic life uses were assessed as "fully supported" based on results of monitoring from the IDNR ambient station at Cedar Falls in 2000 and 2001. Monitoring at this station showed no violations of Class B(WW) water quality criteria for dissolved oxygen, pH, ammonia-nitrogen, toxic metals, and toxic organic compounds in the 14 samples analyzed during this biennial period. Fish consumption uses remain assessed as "fully supported" based on results of U.S. EPA/IDNR fish tissue (RAFT) monitoring at Cedar Falls in 1997 that showed levels of all contaminants were less than ½ of the respective FDA action levels and IDNR levels of concern (see assessment for the 2000 and 1998 reports above).
