Rock Creek IA 02-CED-493

Assessment Comments

Assessment based on 2001, 2008 and 2012 IDNR/SHL biological sampling data: FIBI = 71 (excellent) and 61, 65 (both good), BMIBI = 50 (fair) and 65, 74 (both good) and 2002 Fisheries data: FIBI = 67 (good). FIBI BIC = 36 and BMIBI BIC = 51.

Basis for Assessment

[Note:  Prior to the 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, 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 remain "not assessed" (IR 3a) due to the lack of information upon which to base an assessment.   The Class B(WW-1) aquatic life uses remain assessed (evaluated) as "fully supported"  (IR 2a) based on results of IDNR/SHL biological sampling in 2001, 2008 and 2012 and Fisheries sampling in 2002.   Fish consumption uses remain "not assessed" (IR 3a) due to the lack of fish contaminant monitoring in this stream segment.  

EXPLANATION:  The Class B(WW1) aquatic life uses remain assessed (evaluated) as “fully supporting” based on data collected in 2001, 2008 and 2012 as part of the IDNR/SHL stream biocriteria project and on data collected in 2002 as part of a IDNR Fisheries stream sampling project: Manchester research station.   The 2012 FIBI score was 65 (good) and the BMIBI score was 50 (fair).   The 2008 FIBI score was 61 (good) and the BMIBI score was 74 (good).   The 2001 FIBI score was 71 (excellent) and the 2001 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 1994-2008.   The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51.   This segment passed the FIBI BIC 4/4 times and passed the BMIBI BIC 2/3 times in the last 12 years.  

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology.   IDNR now requires a segment have two or more biological samples collected from the segment in multiple years over a five-year period to be considered “monitored”.   This segment had multiple samples collected in the previous 12 years (2001-2012); however, the samples were not collected during a five-year period.   However, despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.  

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