Sugar Creek IA 02-CED-492

Assessment Comments

Assessment based on (1) 2001 Biocriteria: Fish IBI = 53 (good); BM-IBI = 50 (fair) and (2) TMDL monitoring in 2001.

Basis for Assessment

SUMMARY:  The general aquatic life uses are assessed as "fully supported / threatened."  Sources of information for this assessment include (1) results of biological monitoring conducted in 2001 as part of the DNR/UHL stream biocriteria project and (2) water quality monitoring conducted at one site in this segment from March to November 2001 by IDNR and UHL in support of TMDL development.   EXPLANATION:  The Class B(LR) uses are assessed as "fully supported / threatened" based on results of biological monitoring conducted in 2001.   The biological assessment was based on data collected in 2001 as part of the DNR/UHL stream biocriteria project.   The 2001 Fish IBI score was 53 (good) and the BM-IBI score was 50 (fair).  The aquatic life use support was assessed as "fully supported / threatened" (=FST), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established specifically for the 2002 Section 305(b) report.   The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.   Results of chemical/physical water quality monitoring conducted in 2001 in support of TMDL development show no violations of Class B(LR) state water quality criteria for conventional parameters and ammonia-nitrogen in the nine monthly samples collected between March and November 2001 at the site 2 miles E of Tipton (Site 9) (the maximum value of ammonia-nitrogen was 0.12 mg/l).   These results suggest "full support" of the aquatic life uses.   Biological monitoring, however, is better able to reflect cumulative impacts of water quality over time and thus is believed to more accurately represent water quality conditions of this segment of Sugar Creek than do results from the 2001 monthly TMDL monitoring sites.   Thus, these uses are assessed as "fully supported / threatened."