Bear Creek IA 03-SSK-958

Assessment Comments

Assessment remains based on 2007 and 2008 IDNR/SHL biological sampling data: FIBI = 55 (good) and 71 (excellent); BMIBI = 68, 71 (good). Non-riffle habitat FIBI BIC = 32, BMIBI BIC = 62.

Basis for Assessment

[Note:  Prior to the 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 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 remain "not assessed" (IR 3a) due to the lack of information upon which to base an assessment.   The Class B(WW2) aquatic life uses remain assessed as "fully supported" (IR 2a) based on 2007 and 2008 IDNR/SHL biological sampling data.  

EXPLANATION:  This Class B(WW2) aquatic life uses remain assessment (monitored) as “fully supporting” based on data collected in 2007 and 2008 as part of the IDNR/SHL stream biological sampling project.   A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biological sampling data.   The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species 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 2007 FIBI score was 71 (excellent) and the BMIBI score was 71 (good).   The 2008 FIBI score was 55 (good) and the BMIBI score was 68 (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 non-riffle habitat FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62.   This segment passed the FIBI and BMIBI BICs 2/2 times in the last five years.   The biological impairment criteria were determined from a statistical analysis of biological data collected at stream ecoregion reference sites from 1994-2008.   This assessment is considered "monitored" because there were two or more samples collected in multiple years during a five-year period.