Missouri River IA 06-WEM-1720
from confluence with Little Sioux R. (Harrison Co.) to confluence with Elm Cr. at river mile 691.0 at Decatur NE (=S18 T83N R46W Monona Co.).
- Cycle
- 2016
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 12/5/2016 4:43:26 PM
- Updated
- 1/19/2017 1:46:10 PM
The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" (IR 5a) based on the bacterial impairment of recreation uses identified by the Nebraska Department of Environmental Quality. This is a new impairment for this assessment segment. 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 are assessed (monitored) as “fully supporting” (IR 2a) based on results of fish contaminant monitoring near Blencoe in 2012. The sources of information for this assessment are (1) information from Nebraska fisheries biologists (Mestl) on habitat conditions in the Missouri River and (2) results of fish contaminant monitoring near Blencoe in September 2012.
The Class A1 (primary contact recreation) uses are assessed as "partially supporting" based on the bacterial impairment identified for this assessment segment by the state of Nebraska. A TMDL for the Nebraska impairment in this segment of the Missouri River was approved by EPA in 2007. Because Iowa DNR did not participate in the preparation of this TMDL, this impairment is appropriate for Category 5a of Iowa's Integrated Report.
The Class B(WW1) uses remain assessed (evaluated) as "partially supported" (IR Category 4c, non-pollutant stressor) based on the assessment developed for previous assessment/listing 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.
Fish consumption uses are assessed (monitored) as "fully supported" based on results of U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2012 near Blencoe in Monona County. The composite sample of fillets from Paddlefish had very low levels of contaminants. Levels of primary contaminants were as follows: mercury: 0.0906 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. The fish contaminant data generated from the 2012 RAFT sampling conducted in 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. The Iowa DNR/Dept. of Public Health consumption advisory trigger levels are as follow: mercury: 0.3 ppm; total PCBs: 0.2 pppm, and technical chlordane: 0.6 ppm.