Winnebago River IA 02-WIN-826

Assessment Comments

Assessment is based on (1) IDNR ambient city monitoring downstream form Mason City in 2000-01, (2) fish tissue monitoring in 1998, 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 remain assessed as "fully supported / threatened."  Fish consumption uses remain assessed as "fully supported.".   The sources of data for this assessment include (1) results of monthly monitoring from November 1999 through September 2001 at the IDNR ambient city monitoring station located downstream from Mason City (station 10170003) and (2) results of U.S.  EPA/IDNR fish tissue (RAFT) monitoring in 1998.   The assessment is also based, in part, on water quality studies conducted in 1994 and 1995 for the Lehigh Portland Cement Company.   EXPLANATION:  The Class B(WW) aquatic life uses remain assessed as "fully supported / threatened."  Monitoring at the IDNR city station showed no violations of Class B(WW) water quality criteria for dissolved oxygen or ammonia-nitrogen in the 14 samples collected, for toxic metals in the 14 samples collected, and for toxic organic compounds in the six samples analyzed, during the 2000-2001 biennial period.   Although these results suggest "full support" of the Class B(WW) aquatic life uses, the results of the water quality studies conducted in 1994 and 1995 suggest the possibility of threats to full support (see assessment developed for the 1998 report above).   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 remain assessed as "fully supported" based on results of U.S.  EPA/IDNR fish tissue (RAFT) monitoring in 1998 (see assessment for the 2000 report above).