Assessment Comments
Assessment is based on occurrence of fish kills.
Basis for Assessment
[Note: For the 2002 report, the previous waterbody segment for South Fork Iowa River (IA 02-IOW-0280-2), which extended 22 miles from an unnamed tributary east of Buckeye in Section 19, T88N, R21W, Hardin County to confluence with unnamed tributary in SE 1/4, S35, T90N, R23W, Wright Co., was split into three subsegments: (1) from tributary E of Buckeye to tributary N of Buckeye (IA 02-IOW-0280-3), (2) from tributary N of Buckeye to tributary E of Williams (IA 02-IOW-0280-4), and (3) from tributary E of Williams to Wright Co. tributary (IA 02-IOW-0280-5). See assessment information for segment IA 02-IOW-0280-3 for previous Section 305(b) assessments for the previous 18-mile stream segment.]
SUMMARY: The Class B(LR) aquatic life uses remain assessed (evaluated) as "partially supported" due to occurrence of a fish kill. EXPLANATION: The previous (2000) assessment of the aquatic life uses was based on the occurrence of a fish kill in 1997 (see assessment for the 2000 report above). According to IDNR's assessment methodology for Section 305(b) reporting, occurrence of a single pollution-caused fish kill within the most recent three-year period indicates ongoing impairment of the aquatic life uses. The absence of a fish kill in the three-year period following a fish kill suggest that impacts from the kill have likely dissipated. Because the most recent pollution-caused fish kill occurred on this stream segment prior to the most recent three-year period (1999, 2000, 2001), but occurred no more than six years ago, the aquatic life uses remain assessed as "partially supported." Due to the age of the kill (more than three years old), however, the confidence level for this assessment should be considered relatively low.
