Assessment Comments
Assessment is based on: (1) results of ambient water quality monitoring conducted by USGS at Omaha, NE, (station 06610000) from January 2008 through December 2010, (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 are “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 fish consumption uses are assessed (monitored) as "fully supported" 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 2006 through December 2008, (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.
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 2008-2010 assessment period, however, suggest good water quality in this river segment. No violations of Class B(WW1) criteria occurred in the 37 samples analyzed during this period for ammonia (maximum of 0.78 mg/l), dissolved oxygen (minimum = 6.0 mg/L) or pH (range from 8.0 to 8.7 pH units). Levels of toxic metals (e.g., arsenic) and pesticides (e.g., dieldrin) in the 37 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. Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa. In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol. This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol). Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses. This scenario, however, does not apply to the fish contaminant data generated from the 2005 RAFT sampling conducted in this assessment segment the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.
