Assessment Comments
Assessment is based on (1) LTRMP ambient monitoring from 2002-04, (2) interstate consultation with Illinois EPA in 2010, (3) result of U.S. EPA/IDNR fish contaminant monitoring 2006 and 2008, and (4) results of IDNR follow-up fish contaminant monitoring in 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 "fully supporting" based on results of LTRMP ambient chemical/physical water quality monitoring from 2002 through 2004. Fish consumption uses are assessed (monitored) as "partially supported" based on issuance of a "one meal per week" fish consumption advisory for Pool 12 of the Mississippi River by Iowa DNR in 2007. The sources of data used for this assessment are (1) 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, (2) interstate consultation with Illinois EPA through the UMRBA Water Quality Task Force, (3) results of U.S. EPA/DNR fish tissue (RAFT) monitoring downstream from Dubuque in 2004, 2006, and 2008, and (4) results of IDNR/Fisheries Bureau follow-up fish tissue monitoring at Dubuque in 2007.
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 were assessed (monitored) as “fully supported” based on results of water quality monitoring from LTRMP station M582.5B at the tailwater area of Lock and Dam 11. Results of monitoring from 2002-04 at this station show 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.
Fish consumption uses remain assessed (monitored) as "partially supported" based on IDNR’s issuance of a "one meal per week" fish consumption advisory for Pool 12 of the Mississippi River 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. For the 2006 RAFT sampling, the duplicate composite samples of fillets from common carp and largemouth bass had generally low levels of contaminants. Levels of primary contaminants in the duplicate composite sample of common carp fillets were as follows: mercury: 0.022 and 0.145 ppm; total PCBs: 0.114 and 0.095 ppm; and technical chlordane: 0.003 and 0.022 ppm. Levels of primary contaminants in the duplicate composite sample of largemouth bass fillets were as follows: mercury: 0.206 and 0.311 ppm; total PCBs: 0.09 and 0.09 ppm; and technical chlordane: 0.03 and 0.03 ppm. The level of mercury in the samples of largemouth bass (0.311 ppm) exceeded the IDNR/IDPH trigger level of 0.30 ppm for a one meal per week consumption advisory (this level is well below the “do not eat” trigger level for mercury of 1.0 ppm). According to the IDNR/IDPH advisory protocol, two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed before issuance of a consumption advisory is justified. In response to the elevated level of mercury, the IDNR Fisheries Bureau conducted follow-up monitoring at Dubuque in 2007. Levels of mercury in the composite samples of fillets of largemouth bass and walleye were 0.41 and 0.31 ppm, respectively. Because the level of mercury in samples of largemouth bass fillets from two consecutive samplings exceeded the mercury advisory trigger level, IDNR issued a one meal per week advisory in late 2007. This advisory covers predator fish species in all of Pool 12. According to IDNR’s assessment methodology, the existence of a “one meal per week” consumption advisory indicates that fish consumption uses should be assessed as “partially supported.”
Additional fish contaminant monitoring has been conducted in this assessment segment as part of RAFT trend monitoring. This segment has been sampled for whole-fish common carp since 1994 on an every-other-year basis as part of RAFT trend monitoring. The results from the 2004, 2006, and 2008 trend sampling all show low levels of the primary contaminants (chlordane, PCBs, and mercury). The results for the 2004 sample are as follows: mercury: 0.05 ppm; total PCBs: 0.14 ppm; and technical chlordane: <0.03 ppm. The results for the 2006 sample are as follows: mercury: 0.136 ppm; total PCBs: 0.208 ppm; and technical chlordane: <0.03 ppm and for the 2008 sample are mercury: 0.104 ppm; total PCBs: 0.159 ppm; and technical chlordane: <0.03 ppm. The level of total PCBs in the 2006 whole-fish carp sample (0.208), although approximately equal to the advisory trigger level for total PCBs of 0.2 ppm, does not suggest an immediate concern. That is, levels of chlorinated hydrocarbon contaminants such as PCBs tend to be lower in fillet samples than in whole-fish samples. Thus, a total PCB level of 0.208 ppm in a whole fish sample strongly suggests that levels of total PCBs in fillet samples would be less than the PCB advisory trigger level. The results for the 2008 sample are as follows: mercury: 0.104 ppm; total PCBs: 0.159 ppm; and technical chlordane: <0.03 ppm. Thus, results of RAFT monitoring in this river segment do not suggest the need to issue a consumption advisory for this waterbody for PCBs. Results of future RAFT trend monitoring in this segment will be reviewed to determine if levels of PCBs suggest the need for follow-up monitoring with fillet samples.
