Assessment Comments
Assessment is based on results of (1) ambient monitoring conducted by Illinois EPA, 2010-2012, (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 remain “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 by Illinois EPA. The existing aquatic life impairment due to cadmium is proposed for de-listing due to an error in assessment. Fish consumption uses remain assessed (monitored) as "fully supported." The sources of data used for this assessment are (1) results of monitoring conducted from March 17, 2010 to October 27, 2011 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 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 all eight of the samples analyzed for total aluminum from 2010-2011 exceeded Iowa’s Class B(WW1) chronic criterion for aluminum of 87 ug/l (none of the eight samples analyzed for dissolved aluminum exceeded Iowa’s chronic aquatic life criteria). Two of the eight samples exceeded the acute criterion for aluminum (750 mg/l). The maximum sample value for total aluminum at this station during the 2008-2010 period was 1,170 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 (100 %) 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 2010-2012 period.
The existing impairment of the Class B(WW1) aquatic life uses due to cadmium, however, is proposed for de-listing. A review of the methods used by Iowa DNR to identify the existing impairment for cadmium showed that the impairment was based entirely on estimated data (i.e., data reported as between the method detection level and the reporting limit). As described in the U.S. Geological Survey’s Open File Report 99—193 (Oblinger Childress et al. 1999), estimated data may not be appropriate for addressing regulatory issues:
"[Laboratories] providing estimates of low concentrations gives the user the flexibility to decide when it is appropriate to censor the reporting level and when it is appropriate to use estimated values below the reporting level for interpretations that are based on particular objectives of a study. Some studies require a high degree of certainty for an individual analysis, such as those that address regulatory issues. Others do not require the same high degree of certainty for an individual analysis but rather base interpretation on results from large numbers of samples, such as studies that assess the occurrence of a constituent in the environment."
Given that (1) estimated values may not be appropriate for addressing regulatory issues (such as Section 303(d) listing), (2) all data used to identify violations of Iowa’s chronic aquatic life criteria for cadmium were estimated values, and (3) the Illinois method detection level for cadmium (0.18 ug/l) is below Iowa’s chronic criterion for cadmium (0.45 ug/l), the existing aquatic life impairment based on cadmium is proposed for de-listing for the current (2014) Integrated Reporting Cycle.
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 eight samples collected.
Fish consumption uses remain 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.
