Mississippi River IA 01-NEM-76

Assessment Comments

Assessment based on (1) LTRMP ambient monitoring near Guttenberg from 2002-04 and (2) U.S. EPA/IDNR fish contaminant monitoring in 2000.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment.   The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supporting" based on results of ambient chemical water quality monitoring from 2002 through 2004.   Fish consumption uses remain assessed (monitored) as "fully supported" based on fish contaminant monitoring in 2000.   The sources of data used for this assessment are (1) the results of routine chemical/physical water quality monitoring conducted at station M615.2B at the Lock and Dam 10 tailwater at Guttenberg from January 2002 through September 2004 by IDNR staff of the Upper Mississippi River Long-Term Resource Monitoring Program (LTRMP) at Bellevue, IA and (2) results of U.S.  EPA/DNR fish tissue (RAFT) monitoring in 2000 downstream from Guttenberg.

EXPLANATION:  An assessment of support of the Class A1 (primary contact recreation) uses was not developed due to lack of sufficient data on levels of indicator bacteria in this river reach.   LTRMP monitoring does not include analysis for indicator bacteria.  

Results of water quality monitoring from LTRMP station M615.2B at the tailwater area of Lock and Dam 10 do not suggest water quality concerns with conventional parameters.   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 (evaluated) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring downstream from Guttenberg in 2000.   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.   Prior to 2006, IDNR used action levels published by the U.S.  Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa.   In an effort to make Iowa’s consumption more protective and compatible with the various protocols used by adjacent states, the Iowa Department of Public Health (IDPH), in cooperation with Iowa DNR, developed a risk-based advisory protocol.   This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol).   Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest impairment of, fish consumption uses.  

Although this scenario does not apply to the fish contaminant data generated from the 2000 RAFT sampling conducted in this assessment segment, levels of contaminant are sufficiently high for at least some concern and justify follow-up monitoring.   The levels of at least one contaminant now slightly exceeds one or more advisory trigger levels, thus suggesting the need for additional (follow-up) monitoring to determine whether a consumption advisory should be issued.   The composite samples of fillets from the 2000 RAFT sampling had generally low levels of contaminants.   Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.072 ppm; total PCBs: 0.207 ppm; and technical chlordane: <0.03 ppm.   Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: 0.125 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm.   The level of mercury in the sample of common carp fillets, however, exceeds the IDNR/IDPH trigger level of 0.2 ppm for a one meal per week consumption advisory.   According to the IDNR/IDPH advisory protocol, two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory.   Thus, additional monitoring will be conducted in 2008 to determine whether an advisory is needed for this waterbody.   According to IDNR’s assessment methodology, the occurrence of contaminant slightly above an advisory trigger level does not suggest impairment of the fish consumption uses but does suggest the need to conduct additional fish contaminant monitoring.