Assessment Comments
2014: Assessment is based on (1) results of U.S. EPA/IDNR fish tissue monitoring near Sergeant Bluff in 2004, 2007, and 2012, (2) information from Nebraska fisheries biologists, and (3) results of ambient water quality monitoring by USGS at station 06486000 at Sioux City from June 2011 through August 2012.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses remain “not assessed” (IR 3a) 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 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" (IR 2a) 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, 2007, and 2012 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 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. Although parameter coverage is limited, results of ambient water quality monitoring by USGS from June 2011 to August 2012 at Sioux City do not suggest water quality problems in this segment of river. No violations of Class B(WW1) criteria occurred in the 13 samples analyzed for dissolved oxygen (minimum = 7.4 mg/l) or in the 14 samples analyzed for pH (range: 8 to 8.5 pH units). None of the 230 samples measured for water temperature exceeded the Class B(WW1) criterion of 32C (maximum = 30.7C).
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, 2007, and 2012. 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 composite samples of fillets from paddlefish collected in 2012 also had low levels of contaminants. Levels of primary contaminants in the four-fish composite sample of paddlefish fillets in 2012 were as follows: mercury: 0.0906 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. All these contaminant levels are far below levels of concern for fish consumption. The fish contaminant data generated from the 2004, 2007, and 2012 RAFT sampling conducted at this river segment show that the levels of contaminants and low and do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.
