Assessment Comments
Assessment is based on results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2009 and 2010.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) and Class B(LW) aquatic life uses remain "not assessed" due to a lack of information upon which to base these assessments. The fish consumption uses remain assessed (monitored) as "partially supported" (IR 5a) due to the issuance of a fish consumption advisory at this lake. This assessment remains based on results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2009 and 2010.
EXPLANATION: Fish consumption uses remain assessed (monitored) as “partially supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at McKinley Lake in 2009 and 2010. The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes. The fish contaminant data generated from the 2009 RAFT sampling conducted at McKinley Lake showed that levels of PCBs were sufficiently high for concern and thus justified follow-up monitoring. Results from this sampling showed that the level of PCBs in the sample of channel catfish fillets (0.212 ppm) exceeded the 1 meal/week trigger level (0.2 ppm) as defined in Iowa’s fish consumption advisory protocol. According to IDNR’s assessment methodology, the single occurrence of contaminant above an advisory trigger level neither warrants issuance of an advisory nor indicates impairment of the fish consumption uses: two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory. Follow-up sampling conducted in 2010 showed that levels of PCBs in common carp (0.263 ppm) again exceeded the 1 meal/week trigger level (0.2 ppm). Thus a one meal per week fish consumption advisory was issued for McKinley Lake, and the fish consumption uses are thus assessed as “partially supported.”
