Mississippi River IA 01-NEM-61

The Class A (primary contact recreation) uses are assessed as “partially supported” based on the impairment of primary contact recreation uses identified for this segment of the Upper Mississippi River by the Illinois EPA for the 2016 Section 303(d) listing cycle. The Illinois EPA identified an impairment of primary contact recreation uses in this river segment due to high levels of indicator bacteria (fecal coliforms). This assessment was developed as result of interstate consultation on Section 303(d) listing conducted through the Upper Mississippi River Basin Association’s “Water Quality Task Force” in June 2016.

The assessment of support of the Class B(WW1) aquatic life uses is changed for the current (2016) IR cycle from “fully supported” to “partially supported” due to occurrence of a fish kill in January 2015.  This fish kill occurred at Davenport, IA, on or before January 29, 2015.  Investigators attributed the kill to natural causes. An estimated 270 Freshwater Drum were killed.  The following are notes from the fish kill investigation:

Approximately 270 dead freshwater drum have been reported along the shoreline of the Mississippi River near Davenport.  Fisheries biologists investigated the fish kill that occurred along the river shoreline from Lock and Dam 15 to Credit Island Park. The fish kill was determined to be from natural causes, either oxygen depletion, stress or disease. A similar fish kill of freshwater drum occurred at approximately the same time last year in the same area.

According to IDNR’s assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired”.     If a cause of the kill was not identified during the IDNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated.”    Such assessments, although suitable for Section 305(b) reporting, lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (IR Category 5).  Waterbodies affected by such fish kills will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation.

The assessment of support of the fish consumption uses is based on results of Iowa DNR fish tissue monitoring at two locations: (1) in Pool 17 downriver from Muscatine and (2) in Pool 16 downriver from Davenport near Linwood.  Results from these fish tissue monitoring stations continue to show full support of fish consumption uses.  

Results of Iowa DNR fish contaminant status (fillet) monitoring downstream from Muscatine (Pool 17) in 2012 suggest “full support” of fish consumption uses.  Fillets of common carp and tissue plugs of white bass were analyzed.  Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.046 ppm; total PCBs: 0.09 ppm, and technical chlordane: <0.03 ppm.  The average level of mercury in the 2012 tissue plugs from four white bass was 0.244 ppm.  These results do not exceed Iowa thresholds for issuance of fish consumption advisories and thus suggest “full support” of fish consumption uses.

Results of Iowa DNR fish contaminant trend (whole-fish) and status (fillet) monitoring near Linwood (Pool 16) in 2012 and 2014 also suggest “full support” of fish consumption uses.  Results of whole fish common carp samples at the trend monitoring site near Linwood in 2012 showed low levels of primary contaminants.  Levels of primary contaminants in the composite samples of whole-fish common carp were as follows:  mercury: 0.0733 ppm; total PCBs: 0.187 ppm; technical chlordane:  0.033 ppm. 

The levels of primary contaminants in the 2014 composite sample of common carp fillets from near Linwood were as follows: mercury: <0.05 ppm; total PCBs: 0.06 ppm, and technical chlordane:  <0.1 ppm.  Levels of contaminants in samples of whole fish common carp from the trend monitoring site near Linwood in 2014 showed similarly low levels of primary contaminants:  mercury: 0.09 ppm; total PCBs: <0.24 ppm; technical chlordane:  0.11 ppm.  Note:  the level of total PCBs (<0.24) suggests the possibility of a total PCB concentration of greater than the one-meal-per-week consumption advisory threshold of 0.2 ppm.  Review of the data for the individual Aroclors that comprise total PCBs (Aroclors 1248, 1254, and 1260), however, shows that all Aroclors for this sample were reported as less than the level of detection:  0.08 ppm.  Thus, the sum of the three Aroclors (3 X 0.08 ppm) was 0.24 ppm.  Iowa DNR is working with the lab that conducts these analyses to reduce the level of detection for the individual Aroclors.  In addition, a level of a contaminant above a consumption advisory threshold in a whole-fish sample does not suggest the need to issue a consumption advisory.  That is, according to IDNR’s assessment methodology, the occurrence of levels of PCBs above an advisory trigger level in whole-fish samples—even in consecutive years—does not suggest impairment of the fish consumption uses but does suggest the need to conduct additional fish contaminant monitoring to determine contaminant levels in the edible portion of the fish (fillets).   The IDNR/IDPH advisory protocol states that two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory. 

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.  Results of fish contaminant monitoring in this assessment segment in 2012 and 2014 showed that levels of primary contaminants in fillet samples from predator and bottom-feeding fish species were below thresholds for issuing a one-meal-per-week consumption advisory (mercury:  0.3 ppm; PCBs:  0.2 ppm, and technical chlordane:  0.5 ppm).  These results do not indicate the need for issuance of a consumption advisory; thus, the fish consumption uses are assessed as “fully supported”.