Elk Run IA 02-CED-544

Assessment Comments

Assessment based on results of IDNR/UHL biological (biocriteria) monitoring in 1999: FIBI = 73 (excellent), BMIBI = 64 (good). Non-riffle habitat FIBI BIC = 44, natural substrate BMIBI BIC = 70.

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 (evaluted) as "fully supported" based on results of IDNR/UHL biological (biocriteria) sampling in 1999.   The 1999 biological sampling data are now more than five years old; therefore, this assessment is now considered "evaluated" instead of "monitored."

EXPLANATION:  The assessment of the aquatic life use was based on data collected in 1999 as part of the IDNR/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 1999 FIBI score was 73 (excellent) and the BMIBI score was 64 (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 44 and the natural substrate BMIBI BIC for this ecoregion is 70.   This site passed the FIBI BIC and passed the BMIBI BIC using the BMIBI UAV of 8 points.