Mississippi River IA 01-NEM-75

The Class A1 (primary contact recreation) uses remain “not assessed” due to the lack of information upon which to base an assessment.  Although ambient monitoring is conducted in this river segment by the Illinois EPA, the resulting data are for fecal coliform bacteria.  These data are not applicable to Iowa’s water quality standard for E. coli to protect the designated Class A1 primary contact recreation uses.  Water quality monitoring conducted by other agencies in this river segment (e.g., LTRMP) does not include analysis for indicator bacteria.  

The Class B(WW1) (aquatic life) uses are assessed (monitored) as “not supported” (IR Category 5a) due to violations of aquatic life criteria for toxic metals.  Results of monitoring from Illinois EPA station M-13 show that nine of the 11 samples (82%) analyzed for total aluminum from 2012-2014 exceeded Iowa’s Class B(WW1) chronic criterion for aluminum of 87 ug/l (none of the 11 samples analyzed for dissolved aluminum exceeded Iowa’s chronic aquatic life criteria).  Two of the 11 samples (18%) exceeded the acute criterion for aluminum (750 mg/l).  The maximum sample value for total aluminum at this station during the 2012-2014 period was 2,120 ug/l.  Based on Iowa DNR’s assessment/listing methodology, more than one violation of a chronic or acute water quality criterion for a toxic parameter over a three-year period suggests impairment of aquatic life uses.  Thus, the frequency of violations of the aquatic life criteria for aluminum suggests that the Class B(WW1) aquatic life uses of this assessment segment should be assessed as “not supported” and placed in IR Category 5a.  Monitoring results for other toxic parameters and for conventional parameters (dissolved oxygen, pH, or ammonia-nitrogen) at Station M-13 showed no violations of Class B(WW1) criteria during the 2012-2014 period.  

Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Dubuque in 2013 and downstream from Guttenberg in 2007.  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 average level of mercury in tissue plugs from five Largemouth Bass collected in 2013 near Mud Lake was 0.165 ppm; this level is below the one meal/week consumption advisory trigger of 0.3 ppm.  For the 2007 sampling downstream from Guttenberg, the levels of primary contaminants were also below the advisory trigger levels.  Levels of primary contaminants in the composite sample of common carp fillets in 2007 were as follows: mercury: 0.126 ppm; total PCBs: 0.112 ppm; and technical chlordane: <0.03 ppm.  The level of mercury in the composite sample of white bass fillets was 0.065 ppm.  The levels of contaminants from the 2013 and 2007 RAFT sampling do not exceed any of the advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.