Winnebago River IA 02-WIN-827

Assessment Comments

Assessment is based on results of (1) IDNR/UHL ambient city monitoring upstream from Mason City from 2002-04; (2) two water quality studies conducted for Lehigh Cement Co. in 1994-95, and (3) biological monitoring by the IDNR Fisheries Bureau in 2000.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses are assessed (monitored) as "fully supported " based on results of (1) ambient water quality monitoring from 2002 through 2004 and (2) biological monitoring conducted by the IDNR Fisheries Bureau in 2000.   Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this river segment.   The sources of data for this assessment include (1) the results of ambient monthly water quality monitoring from January 2002 through December 2004 at the IDNR/UHL ambient city monitoring station located upstream from Mason City (STORET station 10170002), (2) the results of biological monitoring conducted as part of water quality studies in 1994 and (2) IDNR Fisheries fish sampling near Fertile in 2000.   The assessment is also based, in part, on historical water quality studies conducted for the Lehigh Portland Cement Company.

EXPLANATION:  The Class B(WW) aquatic life uses are assessed (monitored) as "fully supported " based on results of ambient water quality monitoring from 2002-2004 and on results of biological monitoring conducted in 2000.  

Results of monthly ambient water quality monitoring at the IDNR city station from January 2002 through December 2004 showed no violations of Class B(WW) water quality criteria for either conventional or toxic parameters.   No violations occurred in 47 samples analyzed for dissolved oxygen, in 46 samples analyzed for pH, in 36 samples analyzed for ammonia-nitrogen, in 31 samples analyzed for toxic metals, or in the approximately 10 samples analyzed for pesticides.  

The assessment is also partially based on data collected in 2000 as part of a DNR Fisheries stream sampling project: Manchester research station.   A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the Fisheries sampling data.   The biological metrics are based on the numbers and types of fish species that were collected in the stream sampling reach.   The biological metrics were combined to make a fish community index of biotic integrity (F-IBI).   The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2000 evaluated Fish IBI = 63 (good).   The aquatic life use support was assessed (evaluated) as Fully Supporting (=FS), based on a comparison of the F-IBI score with biological assessment criteria established for previous Section 305(b) reports.   The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.

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 in Winnebago River 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 remain "not assessed" due to the lack of recent fish contaminant monitoring in this river segment.