Assessment Comments
Assessment is based on: (1) results of ambient water quality monitoring conducted by USGS at Omaha, NE, (station 06610000) from January 2010 through December 2012, (2) results of U.S. EPA/IDNR fish tissue (RAFT) monitoring near Council Bluffs in 2005, and (3) information from Nebraska fisheries biologists.
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 fish consumption uses are assessed (monitored) as "fully supported" (IR 2a) based on results of fish contaminant monitoring in 2005. The sources of information for this assessment include (1) results of ambient water quality monitoring conducted by USGS at Omaha, NE, (station 06610000) from January 2010 through December 2012, (2) results of U.S. EPA/IDNR fish tissue (RAFT) monitoring near Council Bluffs in 2005, and (3) information from Nebraska fisheries biologists.
EXPLANATION: The Class A1 (primary contact recreation) uses are considered “not assessed” due to the lack of water quality data upon which to base an assessment. Monitoring conducted by USGS at Omaha does not include indicator bacteria.
The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" (IR Category 4c, non-pollutant stressor) based on the assessment developed for previous reporting cycles (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.
Results of ambient water quality monitoring conducted by USGS during the 2010-2012 assessment period, however, suggest good water quality in this river segment. No violations of Class B(WW1) criteria occurred in the samples analyzed during this period for ammonia (38 samples, maximum of 0.35 mg/l), dissolved oxygen (48 samples, minimum = 6.0 mg/L), pH (47 samples, range from 8.0 to 8.7 pH units), chloride (38 samples), or sulfate (38 samples). No violations of the Class B(WW1) criterion for temperature occurred in the 323 samples collected during the 2010-12 period. Levels of toxic metals (e.g., arsenic and selenium) and pesticides (e.g., chlorpyrifos and dieldrin) in the 36 samples collected were below their respective Class B(WW1) criteria.
Fish consumption uses remain assessed (evaluated) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring south of Council Bluffs in 2005. The composite samples of fillets from common carp and flathead catfish had low levels of contaminants. Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.117 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of flathead catfish fillets were as follows: mercury: 0.039 ppm; total PCBs: 0.102 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. The results of fish contaminant monitoring in this assessment segment from the 2005 RAFT sampling, however, show that the levels of contaminants do not exceed any of Iowa' advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.
