Buttrick Creek IA 04-RAC-1149

Assessment Comments

Assessment based on results of IDNR/UHL biological (biocriteria) monitoring in 2001: FIBI = 36 (fair), BMIBI = 70 (good). Non-riffle habitat FIBI BIC = 32; BMIBI BIC = 62.

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(WW-2) aquatic life uses are assessed (evaluated) as "fully supported"  based on results of IDNR/UHL biological (biocriteria) sampling in 2001.   The 2001 sampling data are now greater than five years old; therefore, this assessment is now considered "evaluated" instead of "monitored".  

EXPLANATION:  This assessment was based on data collected in 2001 as part of the IDNR/UHL stream biocriteria project.  The 2001 FIBI score was 36 (fair) and the BMIBI score was 70 (good).   The aquatic life use support was assessed (evaluated) 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 non-riffle habitat FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62.