Little Sioux River IA 06-LSR-1570

Assessment Comments

Assessment is based on results of IDNR monthly ambient monitoring near Larrabee in 2000-2001.

Basis for Assessment

[Note:  For the 2002 report, the previous waterbody segment for the Little Sioux River (IA 06-LSR-0030-1), which extended 38 miles from the Highway 3 at Cherokee (Cherokee Co.) (approximately equal to confluence with Mill Creek north of Cherokee) to the Linn Grove Dam (Buena Vista Co.), was split into two subsegments:  (1) Highway 3 at Cherokee to confluence with Waterman Creek (O'Brien Co.) (IA 06-LSR-0030-1 - this one) and (2) Waterman Creek to the Linn Grove Dam (Buena Vista Co.) (IA 06-LSR-0030-2).   See previous Section 305(b) assessments from this subsegment for the original 38-mile river reach.]

For the 2002 report:  SUMMARY:  The Class B(WW) aquatic life uses are assessed as "fully supported."  Fish consumption uses remain "not assessed."  This assessment is based on results of IDNR monthly ambient monitoring conducted during the 2000-2001 biennial period near Larrabee (station 10180001 (formerly station 911060)).   EXPLANATION:  Monitoring at the IDNR station near Larrabee showed no violations of Class B(WW) water quality criteria during the 2000-2001 biennial period for dissolved oxygen (minimum value = 6.7 mg/l), pH (range = 7.7 to 8.9 units), or ammonia-nitrogen (maximum value = 0.40 mg/l) in the 24 samples analyzed.   In addition, levels of toxic metals in the four samples analyzed, and levels of pesticides in the six samples analyzed, were all below the analytical level of detection.   These results suggest "full support" of the Class B(WW) aquatic life uses.   Fish consumption uses remain "not assessed due to the lack of recent fish contaminant monitoring in this river reach.