Assessment Comments
Assessment is based on IDNR ambient monthly monitoring in 2000 & 2001 west of Jefferson.
Basis for Assessment
[Note: For the 2002 report, the previous waterbody subsegment for the North Raccoon River (IA 04-RAC-0040-1), which extended 43 miles from Buttrick Creek (Greene Co.) to Highway 286 near Lanesboro in Carroll County, was split into three subsegments: (1) Buttrick Cr. to Short Cr. in Greene Co. (IA 04-RAC-0040-1, this one), (2) Short Cr. to Cedar Cr. near Churdan in Greene Co. (IA 04-RAC-0040-2), and (3) Cedar Cr. near Churdan to Highway 286 near Lanesboro (IA 04-RAC-0040-3). See previous assessments from this subsegment for historic Section 305(b) assessments of the original 43-mile subsegment of the North Raccoon River.]
SUMMARY: The Class A (primary contact recreation) uses are assessed (monitored) as "not supported." The Class B(WW) aquatic life uses are assessed (evaluated) as "fully supported." Support of fish consumption uses remains "not assessed." The source of data for this assessment is the results from the IDNR ambient monthly monitoring station near Jefferson in Greene County (station 10370001 (formerly station 700101)). EXPLANATION: The Class A uses were assessed as "not 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." Sixteen of the 21 samples collected from the Jefferson 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 16 non-runoff-affected samples (227 orgs/100ml) is above the Iowa Class A water quality criterion of 200 orgs/100ml; four of the 16 samples (25%) exceeded the U.S. EPA-recommended single-sample maximum value of 400 orgs/100 ml (these results are nearly identical to those from the IDNR ambient monitoring station upstream on the North Raccoon River near Sac City (10810001)). According to U.S. EPA guidelines for Section 305(b) reporting, geometric means for fecal coliforms that exceed 200 organisms/100 ml indicate nonsupport of primary contact recreation uses (see pgs 3-33 to 3-35 of U.S. EPA 1997b). The Class B(WW) uses are assessed (evaluated) as "fully supported." Results of monitoring at the Jefferson station during the 2000-2001 biennial period show no violations of Class B(WW) (aquatic life) water quality criteria in the 24 samples analyzed for dissolved oxygen, pH, and ammonia, in the four samples analyzed for toxic metals, or in the six samples analyzed for pesticides and other toxic organic compounds. These results suggest that the aquatic life uses of this river segment are "fully supported." Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this river segment (see assessment developed for the 2000 report).
