Winnebago River IA 02-WIN-826

Assessment Comments

Assessment is based on results of (1) IDNR/UHL monthly ambient city monitoring downstream form Mason City from 2002-04, (2) U.S. EPA/IDNR fish contaminant monitoring in 2004, and (3) two water quality studies conducted for Lehigh Cement Co. in 1994-95.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses are assessed (monitored) as "fully supported” based on results of ambient water quality monitoring from 2002 through 2004.   Fish consumption uses are assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2004.   The sources of data for this assessment include (1) results of monthly monitoring from 2002 through 2004 at the IDNR/UHL ambient city monitoring station located downstream from Mason City (STORET station 10170003) and (2) results of U.S.  EPA/IDNR fish tissue (RAFT) monitoring east of Mason City in 2004.   The assessment is also based, in part, on historical water quality studies conducted for the Lehigh Portland Cement Company.  

EXPLANATION: The results of IDNR/UHL water quality monitoring downstream from Mason City (STORET station 10170003) suggest “full support” of the Class B(WW) aquatic life uses.   Monitoring at this station showed no violations of Class B(WW) water quality criteria for dissolved oxygen.  pH, or ammonia-nitrogen in the approximately 35 samples collected, or for pesticides and toxic metals in the 32 samples collected during the 2002-2004 assessment period.  Although these results suggest "full support" of the Class B(WW) aquatic life uses, the results of water quality studies conducted in 1994 and 1995, which showed relatively low diversity of the fish community downstream from Mason City, continue to suggest the possibility of threats to full support of the aquatic life uses within the Mason City urban/industrial area.   These studies are now quite old (approximately 10 years), and their ability to characterize current water quality conditions is doubtful.   Follow-up  monitoring is needed to better determine the status of the aquatic communities of this reach of the Winnebago River and to determine whether the Class B(WW) uses may be impaired.  

Fish consumption uses are assessed (monitored) as "fully supported" based on results of U.S.  EPA/IDNR fish tissue (RAFT) monitoring east of Mason City in 2004.   The composite samples of fillets from common carp and northern pike had low levels of contaminants.   Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.136 ppm; total PCBs: 0.101 ppm; and technical chlordane: < 0.03 ppm.   Levels of primary contaminants in the composite sample of northern pike fillets were as follows: mercury: 0.16 ppm; total PCBs: 0.09 ppm; and technical chlordane: < 0.03 ppm.

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, 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, however, does not apply to the fish contaminant data generated from the 2004 RAFT sampling conducted in this assessment segment:  the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.