Assessment Comments
Assessment is based on results of (1) ambient monitoring conducted by Illinois EPA, 2008-2010, (2) LTRMP ambient monitoring from 2002-04, and (3) EPA/IDNR fish contaminant (RAFT) monitoring in 2006 and 2007.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are considered “not assessed” due to the lack of data upon which to base an assessment. The Class B(WW1) aquatic life uses are assessed (monitored) as "not supporting" (IR Category 5a) based on results of ambient monitoring provided for aluminum and cadmium by Illinois EPA. Fish consumption uses remain assessed (monitored) as "fully supported." The sources of data used for this assessment are (1) results of monitoring conducted from May 6, 2008 to November 3, 2010 by the Illinois Environmental Protection Agency at station M-13 at Lock and Dam 11 at Dubuque (river mile 583), (2) results of routine chemical/physical water quality monitoring conducted at station M582.5B at the Lock and Dam 11 tailwater from January 2002 through September 2004 by IDNR staff of the Upper Mississippi River Long-Term Resource Monitoring Program (LTRMP) at Bellevue, IA, and (3) results of U.S. EPA/DNR fish tissue (RAFT) monitoring in 2006 near Dubuque (Mud Lake) and in 2007 downstream of Guttenberg.
EXPLANATION: The Class A1 (primary contact recreation) uses are considered “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., USGS and 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 all 10 of the samples analyzed for aluminum from 2008-2010 exceeded Iowa’s Class B(WW1) chronic criterion for aluminum of 87 ug/l. Two of the 10 samples exceeded the acute criterion for aluminum (750 mg/l). The maximum sample value for aluminum at this station during the 2008-2010 period was 1,170 ug/l. For cadmium, four of 11 samples analyzed as dissolved cadmium exceeded the respective hardness-dependent chronic criteria (criteria ranged from 0.38 to 0.54 ug/l); three of the 11 samples analyzed for total cadmium exceeded these criteria. 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 (10 violations) and chromium (four violations) 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 at Station M-13 showed no violations of Class B(WW1) criteria during the 2008-2010 period.
Results of water quality monitoring from LTRMP station M582.5B at the tailwater area of Lock and Dam 11 from 2002-04 do not suggest water quality concerns with conventional parameters. Results at this station showed no violations of Class B(WW1) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen in the 17 samples collected. (Note: LTMRP monitoring has not been conducted at this station since 2004.) Similarly, results of IL EPA monitoring at station M-13 at Lock and Dam 11 from 2008-2010 show no violations of dissolved oxygen, pH, or ammonia-nitrogen in the 10 samples collected.
[Note on change in listing methodology regarding toxics: Based on consultation with other Region 7 states and U.S. EPA Region 7 staff in 2007, IDNR's methodology for assessing impairments due to violations of chronic criteria for toxic parameters was changed for the 2008 listing cycle. Prior to the 2008 cycle, IDNR followed a U.S. EPA recommendation (U.S. EPA 1997b, page 3-18) that more than one violation of a water quality criterion for a toxic pollutant in an abundant data set indicates an impairment of aquatic life uses. Because no state in Region 7 collected ambient data with the frequency necessary to accurately identify compliance with a chronic criterion (i.e., to allow calculation of short-term (4-day or 30-day) averages), Region 7 states concluded that another assessment approach (e.g., the 10% rule) was more appropriate. Thus, for the 2008 listing cycle, IDNR identified aquatic life impairments for toxic parameters when significantly more than 10% of the samples exceeded a chronic criterion. This methodology was also used for Iowa’s 2010 listing cycle. For the current (2012) cycle, however, EPA Region 7 informed its states that this “10%” approach to identifying impairments due to toxics would no longer be acceptable. Rather, states were to consider the occurrence of more than one violation of a water quality criterion (chronic or acute) for a toxic parameter over a three-year period as indicating Section 303(d) impairment.]
Fish consumption uses are assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Dubuque in 2006 and downstream of 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 composite samples of fillets from the 2006 RAFT sampling had low levels of contaminants. Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.091 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: 0.204 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. For the 2007 sampling 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 2006 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.
