Rock Creek IA 02-CED-493

Assessment Comments

Assessment based on results of IDNR/UHL biological (biocriteria) monitoring in 2001: FIBI = 71 (excellent), BMIBI = 65 (good) and 2002 Fisheries data: FIBI = 67 (good).

Basis for Assessment

[Note:  Prior to the current (2008) Section 305(b) cycle, this stream segment was designated only for Class B(WW) aquatic life uses, including fish consumption 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 also now presumptively designated for Class A1 (primary contact recreation) uses.   This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]

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-1) aquatic life uses are assessed (monitored) as "fully supported"  based on results of IDNR/UHL biological (biocriteria) sampling in 2001 and Fisheries sampling in 2002.   Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream segment.

EXPLANATION:  The assessment of the Class B(WW1) aquatic life uses was based on data collected in 2001 as part of the IDNR/UHL stream biocriteria project and on data collected in 2002 as part of a IDNR Fisheries stream sampling project: Manchester research station.   The 2001 FIBI score was 71 (excellent) and the BMIBI score was 65 (good).   The 2002 Fisheries FIBI score was 67 (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 36 and the BMIBI BIC for this ecoregion is 51.

Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream segment