Assessment Comments
Assessment is based on results of IDNR/UHL ambient city monitoring from 2000-02.
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.]
SUMMARY: The Class B(WW) aquatic life uses are assessed (monitored) as "fully supported / threatened" due to a violation of the state water quality standard for copper. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this river segment. The source of data for this assessment is the results of monthly monitoring from May 2000 through December 2002 at the IDNR/UHL ambient city monitoring station located downstream from Spencer at the County Road M50 bridge east of Spencer (STORET station 10210003).
EXPLANATION: The Class B(WW) aquatic life uses are assessed as "fully supported / threatened" due to a single violation of the state water quality standard for copper. Monitoring at this IDNR/UHL city station showed no violations of Class B(WW) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen in the 28 samples collected, or for pesticides in the nine samples analyzed, during the 2000-2002 assessment period. A violation of Class B(WW) chronic criteria for toxic metals, however, did occur. One of the 28 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. None of the 28 samples contained levels of other toxic metals that violated state water quality criteria. Based on IDNR'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.
