Assessment Comments
Assessment is based on results of water quality monitoring conducted in 2001 by IDNR and UHL in support of TMDL development.
Basis for Assessment
[NOTE: For the 2002 report, the previous waterbody segment IA 02-SHL-0020-0, which extended 46 miles from the Winnebago River to the Iowa/Minnesota state line, was split into two subsegments: (1) Winnebago River to Rose Creek (aka Plymouth Cr. or Beaver Cr.) (IA 02-SHL-0020-1) and (2) Rose Creek to the Iowa/Minnesota state line (IA 02-SHL-0020-2). The assessment developed for previous Section 305(b) reports (see above) refer to the previous 46-mile assessment segment named IA 02-SHL-0020-0.]
The Class A (primary contact recreation) uses are assessed (evaluated) as "fully supported." The Class B(WW) aquatic life uses remain assessed (evaluated) as fully supported / threatened." Fish consumption uses are "not assessed." The sources of data for this assessment is (1) results of monthly monitoring conducted near Rockford from April to November 2001 by IDNR/UHL in support of TMDL development and (2) anecdotal information and best professional judgement used to develop assessments for the 1998 and 2000 reports (see above). EXPLANATION: The Class A (primary contact recreation) uses were assessed as "fully 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." Five of the 7 samples collected from the Rockford station during the 2001 recreational seasons were collected at flows not materially affected by surface runoff. The geometric mean level of indicator bacteria (fecal coliforms) in these 5 non-runoff-affected samples (73 orgs/100ml) is well-below the Iowa Class A water quality criterion of 200 orgs/100ml. None of the five samples had levels of fecal coliforms 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 the geometric mean is less than 200 orgs/100 ml, and if 10% or less of the samples exceed the single-sample maximum value of 400 orgs/100 ml, the primary contact recreation uses are "fully 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" and is thus of a lower confidence than a "monitored" assessment. The Class B(WW) uses remain assessed as "fully supported / threatened" based on anecdotal information that nutrient enrichment of the river tends to produce nuisance levels of algae in summer (see assessments developed for the 1998 and 2000 reports above). Results of monitoring conducted near Rockford in 2001 in support of TMDL development, however, show no violations of state water quality criteria for conventional parameters in the eight monthly samples collected between April and November 2001 (samples were not analyzed for toxic metals or pesticides). Fish consumption uses were "not assessed" due to the lack of recent fish tissue monitoring in this river segment.
