Assessment Comments
Assessment based on results of (1) IDNR/UHL monitoring conducted in support of TMDL development, (2) IDNR/UHL Biocriteria sampling in 1999 and 2001.
Basis for Assessment
SUMMARY: The Class B(WW) aquatic life uses are assessed as “not supporting” due to results of DNR/UHL biological monitoring that show regionally poor biological integrity. Fish consumption uses were “not assessed” due to the lack of fish contaminant monitoring in this river reach.
EXPLANATION: The aquatic life use assessment was based on data collected in 1999 and 2001 as part of the DNR/UHL stream biocriteria and TMDL development projects. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and 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) and a benthic macroinvertebrate index (BM-IBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 1999 Fish IBI score was 27 (fair) and the BM-IBI score was 47 (fair). The 2001 Fish IBI scores were 29, 33, 26 (fair), and the BM-IBI scores were 47 (fair), 52 (good), 48 (fair). The aquatic life use support was assessed as "not supporting (=NS)", 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.
