Assessment Comments
Assessment is based on results of IDNR/UHL biological (biocriteria) sampling in 2000: Fish IBI= 36(fair), 66(good); BM-IBI= 45,(fair),62(good).
Basis for Assessment
SUMMARY: The Class B(LR) aquatic life uses are assessed (monitored) as "partially supported" based on results of IDNR/UHL biological (biocriteria) sampling in 2000.
EXPLANATION: The Class B(LR) aquatic life uses continued to be assessed as "partially supported" based on results of DNR/UHL biological (biocriteria) monitoring in 2000. 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 2000 Fish IBI scores were 36 (fair) and 66 (good); the BM-IBI scores were 45 (fair) and 62 (good). The aquatic life use support was assessed as partially supporting (=PS), 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.
A fish kill occurred in Indian Creek at Marion on August 25, 1998. This kill occurred following the injection of approximately 90 gallons of termaticide at a residence. Approximately 2.25 miles of stream were affected; an estimated 43,300 fish were killed; the party responsible for the kill was identified and restitution was sought. According to IDNR's assessment methodology, the absence of a fish kill in the three-year period following a fish kill suggest that impacts from the kill have dissipated. Thus, due to the lack of a subsequent kill in this stream reach, and due to the enforcment action taken by IDNR in response to this kill, the occurrence of the fish kill in 1998 is no longer a factor in determining the degree to which the aquatic life uses are supported.
