Mississippi River IA 01-NEM-71

Assessment Comments

Assessment is based on (1) LTRMP ambient monitoring from 2002-04, (2) interstate consultation with Illinois EPA in 2012, (3) result of U.S. EPA/IDNR fish contaminant trend monitoring 2006, 2008 and 2010, and (4) results of IDNR follow-up fish contaminant monitoring in 2007, 2009, and 2010.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses are considered “not assessed” due to the lack of monitoring information upon which to base an assessment.   The Class B(WW1) aquatic life uses remain 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 "fully supported" based on the removal of the "one meal per week" fish consumption advisory for Pool 12 of the Mississippi River in 2011.   This assessment represents a de-listing of the previous fish consumption impairment.   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) result of U.S.  EPA/IDNR fish contaminant trend monitoring 2006, 2008 and 2010, and (4) results of IDNR follow-up fish contaminant monitoring in 2007, 2009, and 2010.  

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., LTRMP) does not include analysis for indicator bacteria.  

The Class B(WW1) (aquatic life) uses remain 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 are assessed (monitored) as "fully supported" based on the removal of the "one meal per week" fish consumption advisory for this Pool 12 of the Mississippi River.    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.    Levels of mercury in samples of largemouth bass from consecutive samplings exceeded advisory trigger levels, thus suggesting the need for a consumption advisory in 2007.

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), however, exceeded the IDNR/IDPH trigger level of 0.30 ppm for a one meal per week consumption advisory (this levels 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 show that contaminant levels 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 all of Pool 12.

Follow-up monitoring was again conducted in 2009 and 2010.    The level of mercury in composite samples of largemouth bass fillets collected near Sabula in 2009 was 0.153 ppm, which is below the advisory trigger level.    IDPH/IDNR protocol requires two consecutive samples with mercury levels below the advisory trigger level prior to removal of a fish consumption advisory.    Additional monitoring was conducted in 2009 and 2010 in Dubuque near Hamm Island.    The level of mercury in composite samples of largemouth bass fillets was 0.193 ppm in 2009, and 0.188 ppm in 2009.    The level of mercury in composite samples of walleye fillets was 0.234 ppm in 2009, and 0.207 in 2010.    All of these levels are below the advisory trigger level.    Because two consecutive fillet samples showed levels of mercury below the advisory trigger level, the fish consumption advisory was removed for Pool 12 of the Mississippi River.

Additional fish contaminant monitoring has been conducted in this assessment segment as part of RAFT 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.      The results for the 2008 sample are as follows:  mercury: 0.104 ppm; total PCBs: 0.159 ppm; and technical chlordane: <0.03 ppm.    The results for the 2010 sample are as follows:  mercury: 0.111 ppm; total PCBs: 0.277 ppm; and technical chlordane: 0.031 ppm.    The level of total PCBs in the 2006 and 2010 whole-fish carp sample (0.208 ppm and 0.277 ppm, respectively)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 or 0.277 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.    Thus, results of RAFT monitoring in this river segment do not suggest the need to issue a consumption advisory for this waterbody for PCBs.