Assessment Comments
Assessment is based on (1) surveys of Nebraska fisheries biologists and consultation with IDNR staff and (2) U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2000.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are “not assessed” due to the lack of data upon which to base an assessment. This segment was incorrectly identified by IDNR as impaired by bacteria on Iowa’s previous (2006) Section 303(d) list. This change in assessment represents a de-listing of this bacterial impairment. The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" 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 2000. The sources of information for this assessment include (1) results of U.S. EPA/IDNR fish tissue (RAFT) monitoring near Nebraska City in August 2000, (2) information from Nebraska fisheries biologists, and (3) 2008 assessment information from Nebraska DEQ.
EXPLANATION: The Class A1 (primary contact recreation) uses are “not assessed.” The previous bacterial impairment identified for this river segment by IDNR was incorrectly based on data collected by the Nebraska Department of Environmental Quality. These data were collected approximately 60 miles downriver from the Iowa state line; thus, the data are of questionable relevance to bacterial levels in Missouri River assessment segment IA 06-WEM-0010_0.
The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" 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 impairment is appropriate for Integrated Report Category 4c (impairment is not caused by a pollutant). 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 Nebraska City in 2000. The composite samples of fillets from channel catfish and flathead catfish had low levels of contaminants. 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 had previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses. This scenario, however, did not apply to the fish contaminant data generated from the 2000 RAFT sampling conducted in this assessment segment: the levels of contaminants did not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.
