Pilot Branch IA 05-NSH-1424

Assessment Comments

Assessment is based on results of IDNR/UHL biological (biocriteria) monitoring in 2002: FIBI = 31 (fair), BMIBI = 50 (fair). FIBI BIC = 31, BMIBI BIC = 54.

Basis for Assessment

SUMMARY:  The general aquatic life uses are assessed (evaluated) as "fully supported" (minor impacts) based on results of IDNR/UHL biological (biocriteria) sampling in 2002.   The assessment type is considered "evaluated" (relatively lower confidence assessment) due to the uncertainty of using biological assessment methods developed for Class B(LR) and wadable Class B(WW) streams for assessing aquatic life conditions in general use-only stream segments.

EXPLANATION:  The assessment was based on data collected in 2002 as part of the DNR/UHL stream biocriteria project.  The 2002 FIBI score was 31 (fair) and the BMIBI score was 50 (fair).   The aquatic life use support was assessed as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 31 and the BMIBI BIC for this ecoregion is 54.   Even though this site passed both the FIBI and BMIBI BICs, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small general use stream and doesn’t fall in the calibrated watershed size.