Brush Creek IA 01-VOL-317

Assessment Comments

Assessment is based on results of IDNR/UHL biological (biocriteria) sampling in 2005: FIBI = 80 (excellent), BMIBI = 61 (good). FIBI BIC = 52, BMIBI BIC = 61.

Basis for Assessment

[Note:  Prior to the current (2008) Section 305(b) cycle, this stream segment was designated only for Class B(LR) aquatic life uses.   Due to changes in Iowa’s surface water classification that were approved by U.S.  EPA in February 2008 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment is now presumptively designated for Class A1 (primary contact recreation) uses.   The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses).   Thus, for the current (2008) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]

SUMMARY:  The presumptive Class A1 (primary contact recreation) uses are "not assessed" due to the lack of information upon which to base an assessment.   The Class B(WW2) aquatic life uses are assessed (monitored) as "fully supporting"  based on results of IDNR/UHL biological (biocriteria) sampling in 2005.

EXPLANATION:  The assessment of the Class B(WW2) aquatic life uses was based on data collected in 2000 as part of the DNR/UHL stream biocriteria project.   The 2000 FIBI score was 80 (excellent) and the BMIBI score was 61 (good).  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 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 FIBI BIC for this ecoregion is 52 and the BMIBI BIC for this ecoregion is 61.