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 2000-02; (2) two water quality studies conducted for Lehigh Cement Co. in 1994-95, and (3) 2000 IDNR Fisheries data: Fish IBI = 63 (good).

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses remain assessed (evaluated) as "fully supported / threatened" based on results of biological monitoring conducted as part of water quality studies in 1994/1995 and IDNR Fisheries monitoring in 2000.   Neither results of ambient water quality monitoring from 2000-02 nor results of IDNR Fisheries sampling in 2000, however, suggest any threats or impairment to full support of these uses.   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 monthly water quality monitoring from May 2000 through December 2002 at the IDNR 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 1995 for the Lehigh Portland Cement Company, and (3) IDNR Fisheries fish samping near Fertile in 2000 (see below).  

EXPLANATION:  The Class B(WW) aquatic life uses remain assessed (evaluated) as "fully supported / threatened" based on results of biological monitoring conducted in 1994 and 1995.   Because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions—and nearly too old (greater than 10 years) to support any assessment of current conditions)—the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively high confidence).  

Results of recent ambient water quality monitoring at the IDNR city station, however, showed no violations of Class B(WW) water quality criteria for dissolved oxygen or ammonia-nitrogen in the 31 samples collected, for toxic metals in the 28 samples collected, and for toxic organic compounds in the nine samples analyzed, during the 2000-2002 assessment period.   Although these results of chemical/physical monitoring suggest "full support" of the Class B(WW) aquatic life uses, the results of biological sampling conducted for the Lehigh studies 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 (see assessment developed for Winnebago River segment IA 02-WIN-0010-1 developed for the 1998 reporting cycle).   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.  

The assessment was 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.
However, it was decided to keep the aquatic life uses as "fully supported/threated" because the 2000 Fisheries site was located above the city of Mason City; therefore, we do not know if the cement company is still having impacts on the aquatic community.   More monitoring is needed to determine the current impacts.

Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this river segment.