Assessment Comments
Assessment is based on (1) results of U.S. EPA/IDNR fish tissue monitoring near Sergeant Bluff in 2004 and 2007 and (2) information from Nebraska fisheries biologists.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are considered “not assessed” due to the lack of information upon which to base an assessment. The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" (IR Category 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 human health/fish consumption uses remain assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2004 and 2007. The sources of information for this assessment include (1) results of U.S. EPA/IDNR fish tissue monitoring near Sergeant Bluff in 2004 and 2007 and (2) information from Nebraska fisheries biologists.
EXPLANATION: The Class A1 (primary contact recreation) uses are considered “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 Category 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 remain assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Sergeant Bluff in 2004 and 2007. The composite samples of fillets from common carp, flathead catfish, and freshwater drum had low levels of contaminants. Levels of primary contaminants in the composite sample of common carp fillets in 2004 were as follows: mercury: 0.101 ppm; total PCBs: 0.09 ppm; and technical chlordane: 0.043 ppm. Levels of primary contaminants in the composite sample of flathead catfish fillets in 2004 were as follows: mercury: 0.062 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 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. Follow-up sampling conducted in 2007 showed that levels of primary contaminants in the composite sample of freshwater drum fillets were as follows: mercury: 0.195 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. The fish contaminant data generated from the 2004 and 2007 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.
