Assessment Comments
Assessment remains based on (1) results of U.S. EPA/IDNR fish tissue monitoring near Little Sioux in 2009 and (2) information from Nebraska fisheries biologists.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses remain “not assessed” (IR 3a) due to lack of information upon which to base an assessment. The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" (IR 4c) based on information from local fisheries biologists on impacts related to flow modification and habitat alterations in this segment of the Missouri River. The fish consumption uses remain assessed (monitored) as "fully supported" (IR 2a) based on results of fish contaminant monitoring in 2009. The sources of information for this assessment include (1) results of U.S. EPA/IDNR fish tissue monitoring near Little Sioux in 2009 and (2) information from Nebraska fisheries biologists.
EXPLANATION: The Class A1 (primary contact recreation) uses remain “not assessed” due to the lack of information upon which to base an assessment.
The Class B(WW1) uses remain assessed (evaluated) as "partially supported" (IR 4c, non-pollutant stressor) based on the assessment developed for the 1998, 2000, and 2002 reports (i.e., habitat alterations and flow modifications that resulted from development of the river for navigation uses in the mid-Twentieth Century). This assessment was developed in consultation with the Missouri River fisheries biologist for the state of Nebraska.
Fish consumption uses are assessed (monitored) as "fully supported" based on results of U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2009 near Little Sioux in Harrison County. The composite samples of fillets from channel catfish and flathead catfish had very low levels of contaminants. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.0617 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. The level of mercury in the composite sample of flathead catfish fillets was 0.156 ppm. The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses. The fish contaminant data generated from the 2009 RAFT sampling conducted at this river segment show that the levels of contaminants do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.
