Assessment Comments
Assessment based on 2000 biocriteria data: FIBI = 21 (poor), BMIBI = 31 (fair). FIBI non-riffle BIC = 32, BMIBI BIC = 62.
Basis for Assessment
SUMMARY: The Class B(LR) aquatic life uses remain assessed as "partially supported" based on results of biological monitoring in 2000. The full biological monitoring in 2000 suggests "partially supporting". Because of the segment's proximity to the upstream marsh, and the marsh-like qualities of the year 2000 site, it was determined to loosely apply the biological criteria and enter this assessment as evaluated. According to IDNR's assessment methodology, "evaluted" impairments are of relatively lower confidence that “monitored" which have relatively higher confidence. Such "evaluated" waters, while not appropriate for addition to Category 5 of the Integrated Report (= Section 303(d) list), will be placed in either Category 2b or 3b of the IR and thus will be added to the state’s list of “waters in need of further investigation”.
The assessment was based on data collected in 2000 as part of the DNR/UHL stream biocriteria project. 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 (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2000 FIBI score was 21 (poor) and the BMIBI score was 31 (fair). The aquatic life use support was assessed as partially supporting (= PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The non-riffle FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62.
