Assessment Comments
The source of data for this assessment is results of EPA/IDNR fish contaminant (RAFT) monitoring at Cedar Lake in 2004 and 2006.
Basis for Assessment
SUMMARY: The general aquatic life uses were not assessed due to the lack of information upon which to base an assessment. Fish consumption uses remain assessed as impaired due to the continuance of the fish consumption advisory at this lake: levels of PCBs in bottom-feeding fish suggest the need to continue the existing fish consumption advisory at this lake. The source of data for this assessment is results of EPA/IDNR fish contaminant (RAFT) monitoring at Cedar Lake in 2004 and 2006.
Note: A TMDL for chlordane at Cedar Lake was prepared by IDNR and approved by EPA in 2001; thus, this lake was placed into IR Category 4a (TMDL approved) for the 2004 assessment/listing cycle. Because the 2006 and 2008 Section 303(d) impairment due to PCBs was not addressed in the TMDL, this waterbody remains in IR Category 5a (impaired; TMDL needed) for the 2008 assessment/listing cycle.
EXPLANATION: Because data are not available to develop an assessment of support of the Class B(LW) (aquatic life) uses, these uses are considered "not assessed."
Fish consumption uses were assessed (monitored) as “partially supported” based the existence of a fish consumption advisory at this lake and on results of ongoing U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Cedar Lake in 2004 and 2006. 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 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 either a threat to, or impairment of, fish consumption uses. This scenario applies to the fish contaminant data generated from the RAFT sampling conducted in Cedar Lake: levels of chlordane and PCBs exceeded advisory trigger levels in the samples of channel catfish and common carp from the 2002 RAFT, levels of PCBs in the sample of channel catfish exceeded the advisory trigger level for PCBs in the 2004 RAFT, and levels of PCBs in the samples of channel catfish and carp exceeded the advisory trigger level for PCBs in the 2006 RAFT sampling. These results suggest the continued need for a consumption advisory at Cedar Lake. Levels of total chlordane were below the advisory trigger level (0.6 ppm) in both 2004 and 2006 samples. 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”.
A fish consumption advisory has existed at Cedar Lake since 1986. Because of this advisory, Cedar Lake has been monitored as part of the RAFT program on an every-other-year basis since 1986. According to the IDNR/IDPH advisory protocol, two consecutive samplings showing that contaminant levels are below the trigger level in fillet samples are needed to rescind an existing consumption advisory. Levels of chlordane in bottom feeding fish have decreased in 2004 and 2006 and therefore the fish consumption advisory based on chlordane has been removed from this lake. However, levels of PCBs continue to exceed the advisory trigger level, therefore continuance of the existing advisory, and the impairment of fish consumption uses is justified.
