Cedar River IA 02-CED-462

Assessment Comments

Assessment is based on results of (1) IDNR/UHL ambient city monitoring at Gilbertville from 2002-04 and (2) U.S. EPA/IDNR fish tissue (RAFT) monitoring in 1997.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported" based on results of IDNR/UHL ambient water quality monitoring.   Fish consumption uses were assessed (evaluated) as "fully supported" based on results of fish contaminant monitoring in 1997.   The sources of data for this assessment are (1) the results of monthly monitoring from January 2002 through December 2004 at the IDNR ambient city monitoring station located at downstream from Waterloo at County Road D38 bridge at Gilbertville (STORET station 10070006) and (2) the results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring in 1997.  

EXPLANATION:  The Class B(WW) aquatic life uses were assessed as "fully supported" based on results of monitoring from the IDNR ambient station at Gilbertville from 2002 through 2004.   Monitoring at this station showed no violations of Class B(WW) water quality criteria for dissolved oxygen, pH, ammonia-nitrogen, toxic metals, and toxic organic compounds in the approximately 30 samples analyzed during this assessment period; none of the 7 samples analyzed for pesticides exceeded their respective Class B(WW) criteria.  

Fish consumption uses are assessed (evaluated) as "fully supported " based on the 1997 EPA/IDNR fish tissue (RAFT) sampling on the Cedar River near Gilbertville.   This site was sampled for whole-fish common carp as part of an upstream/downstream comparison in the early and mid-1990s.   Both of the whole-fish samples of common carp had generally low levels of the primary contaminants (mercury, total PCBs, and technical chlordane).   While results from this sampling show that levels of chlordane and mercury are well below levels of concern, the level of total PCBs in one of the samples, however, exceeded the 1 meal/week trigger level as defined in Iowa’s revised (2006) fish consumption advisory protocol.   Because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).  

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.   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, 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.   Although this scenario does not apply to the fish contaminant data generated from the 1997 RAFT sampling conducted in this assessment segment, levels of contaminant are sufficiently high for concern and justify follow-up monitoring.

Results from the 1997 sampling show that the level of total PCBs in the sample of whole-fish common carp (0.38 ppm) exceeds the 1 meal/week trigger level of 0.2 ppm as defined in Iowa’s revised (2006) 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.   Also, the age of the data (approaching 10 years), combined with the nationwide trend of declining levels of PCBs in fish over time, suggests that additional monitoring is justified before any decisions are made on issuance of consumption advisories.   But, this elevated level does indicate a concern and the need to conduct additional monitoring to better define contaminant levels in fish from this river segment.   Thus, follow-up monitoring will be is scheduled for 2008 to better determine (1) levels of PCBs in the edible portions (fillets) of fish in this river segment and (2) whether a one-meal-per-week consumption advisory needs to be issued.