Howerdon Creek IA 04-LDM-1110

Assessment Comments

Assessment based 2009 IDNR/SHL biological sampling data: FIBI = 47 (fair), BMIBI = 68 (good). FIBI BIC = 36, BMIBI BIC = 51.

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, 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(WW-2) aquatic life uses are assessed (evaluated) as "fully supported” (IR 2a) based on results of IDNR/SHL biological sampling in 2009.  

EXPLANATION:  The Class B(WW2) aquatic life uses remain assessed (evaluated) as “fully supporting” based on biological data collected in 2009 as part of the IDNR/SHL stream biocriteria project.   The 2009 FIBI score was 47 (fair) and the BMIBI score was 68 (good).   The aquatic life use support was assessed (evaluated) as fully supported (=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 both the FIBI and BMIBI BICs in 2009.  

This aquatic life assessment is considered "evaluated" because there were not two or more samples collected from this segment in multiple years over a five-year period.   Despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.