Assessment Comments
Assessment is based on results of IDNR ambient monthly monitoring near Hornick in 2000 & 2001.
Basis for Assessment
[Note: For the 2002 report, the previous waterbody segment for the West Fork Little Sioux River (IA 06-LSR-0120-0), which extended 32 miles from its mouth to confluence with Mud Creek near Moville in Woodbury Co., was split into two subsegments: (1) mouth to confluence with an unnamed tributary 0.5 miles north of Climbing Hill (Woodbury Co. - this one) (IA 06-LSR-0120-1) and (2) unnamed tributary 0.5 miles north of Climbing Hill to Mud Creek near Moville, Woodbury Co. (IA 06-LSR-0120-2). See previous Section 305(b) from this subsegment for the assessments of the original 32-mile river reach.]
SUMMARY: The Class B(LR) aquatic life uses are assessed as "fully supported / threatened." This assessment is based on results of IDNR monthly ambient monitoring conducted during the 2000-2001 biennial period on West Fork Ditch at the Highway 141 bridge approximately 1 mile east of Hornick in (station 10970001). EXPLANATION: Previous assessments of the aquatic life uses of this stream segment ("fully supported / threatened") were based on biological data collected in 1995 (see assessments for the 1996, 1998 and 2000 reports). These data are now considered too old (greater than five years) for accurately characterzing current water quality conditions. Monitoring at the IDNR station east of Hornick showed no violations of Class B(WW) water quality criteria in the 12 samples collected during the 2000-2001 biennial period for dissolved oxygen (minimum value = 7.1 mg/l), pH (range = 8.1 to 8.5 units), or ammonia-nitrogen (maximum value = 1.80). Levels of pesticides in the four samples analyzed were all below the analytical level of detection; samples from this station were not analyzed for toxic metals during the biennial period. Although these results suggest "full support" of the Class B(WW) aquatic life uses, the extensive habitat alterations in this stream system suggest at least a threat to full support of the aquatic life uses. Thus, these uses were assessed as "fully supported / threatened" (no declining trend) for the 2002 report.
