Assessment Comments
Assessment is based on results of (1) ambient monitoring conducted by Illinois EPA, 2006-08, (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 assessed (monitored) as “fully supported” based on the 2010 assessment developed by the Illinois EPA. The Class B(WW1) aquatic life uses are assessed (monitored) as "not supporting" based on results of ambient monitoring provided for aluminum by Illinois EPA. This is a new Section 303(d) impairment for this assessment segment. Fish consumption uses remain assessed (monitored) as "fully supported." The sources of data used for this assessment are (1) results of monitoring conducted from February 22, 2006 to October 22, 2008 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 assessed (monitored) as “fully supported” based on the results of ambient monitoring for indicator bacteria as conducted by the Illinois EPA. This assessment was developed as result of interstate consultation on Section 303(d) listing conducted in May 2010 through the Upper Mississippi River Basin Association’s “Water Quality Task Force.” 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.” 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 2006-2008 show no violations of dissolved oxygen, pH, or ammonia-nitrogen in the 12 samples collected.
Results of monitoring from Illinois EPA station M-13, however, show that nine of 11 samples analyzed for aluminum from 2006-08 exceeded Iowa’s Class B(WW1) chronic criterion for aluminum of 87 ug/l. The maximum sample value for aluminum at this station during the 2006-2008 period was 1,100 ug/l; the mean and median values were 350 ug/l and 310 ug/l, respectively. Based on IDNR’s Section 303(d) listing methodology, these results suggest that significantly more than 10 percent of the samples exceed Iowa’s chronic criterion for aluminum and thus suggest an impairment of the Class B(WW1) aquatic life uses. [Note: the chronic/acute criteria for aluminum used for the previous (2008) assessment were 388 and 4,539 ug/l respectively; these criteria were changed in the Iowa Water Quality Standards to 87 and 750 ug/l, respectively in 2007. Iowa’s aquatic life criteria for metals are expressed as “total recoverable.”] One of 12 samples violated the chronic criterion for cadmium, copper, and silver. According to the IDNR assessment/listing methodology, the frequencies of violations of the chronic criteria for these metals are not significantly greater than 10% and thus do not indicate an impairment. Monitoring results for other toxic parameters and for conventional parameters at Station M-13 showed no violations of Class B(WW1) criteria during the 2006-2008 period.
Note: 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. Prior to the 2008 listing 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 collects 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.
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.
