Assessment Comments
Assessment is based on results of IDNR ambient city monitoring in 2000 & 2001.
Basis for Assessment
[Note: For the 2002 report, the previous waterbody segment for the Little Sioux River (IA 06-LSR-0030-2), which extended 45 miles from the Linn Grove Dam (Buena Vista Co.) to the Ocheyedan River at Spencer (Clay Co.), was split into three subsegments: (1) Linn Grove Dam to Willow Creek in southern Clay Co (IA 06-LSR-0030-3, (2) Willow Creek to the east corporate limit of Spencer (Clay Co.) (IA 06-LSR-0030-4 - this one), and (3) east corporate limit of Spencer to confluence with the Ocheyedan River at Spencer (IA 06-LSR-0030-5). These subsegments are renumbered to account for the splitting of the adjacent downstream subsegment (IA 06-LSR-0030-1). See previous Section 305(b) assessments from subsegment IA 06-LSR-0030_3 for assessments for the original 45-mile river reach.]
For the 2002 report: SUMMARY: The Class B(WW) aquatic life uses are assessed as "fully supported / threatened." Fish consumption uses remain "not assessed." The source of data for this assessment is the results of monthly monitoring from October 1999 through September 2001 at the IDNR ambient city monitoring station located downstream from Spencer at the County Road M50 bridge east of Spencer (station 10210003). EXPLANATION: The Class B(WW) aquatic life uses are assessed as "fully supported / threatened." Monitoring at the IDNR city station showed no violations of Class B(WW) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen in the 14 samples collected, or for pesticides in the six samples analyzed, during the 2000-2001 biennial period. Violations of Class B(WW) chronic criteria for toxic metals, however, did occur. One of the 14 samples analyzed for toxic metals exceeded the chronic Class B(WW) criterion for copper. The sample collected on October 9, 2000 contained 130 ug/l of copper; the level far exceeded the Class B(WW) chronic and acute criteria for copper of 35 ug/l and 60 ug/l, respectively. According to U.S. EPA guidelines for Section 305(b) reporting (U.S. EPA 1997b, page 3-18), this one violation of a toxic contaminant in a dataset of at least 10 samples collected over a three-year period does not suggest an impairment of the aquatic life uses. Based on DNR's assessment methodology for Section 305(b) reporting, however, this violation suggests that the Class B(WW) aquatic life uses should be assessed as "fully supported/threatened." Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring data for this river segment.
