Deep Creek IA 01-VOL-1876

Assessment Comments

Assessment was based on 2000 and 2005 IDNR/UHL biological monitoring data: FIBI = 73 (good), 70 (good); BMIBI = 75 (good), 79 (excellent). FIBI BIC = 52; BMIBI BIC = 61.

Basis for Assessment

[Note:  Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general 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 and for Class B(WW1) aquatic life uses.   According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters.   Thus, for the current (2010) assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.]

SUMMARY:  The presumptive Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment.   The presumptive Class B(WW1) aquatic life uses are assessed (evaluated) as “fully supported” based on results of IDNR/UHL biological (biocriteria) monitoring in 2000 and 2005.  

EXPLANATION:  This evaluated biological assessment of the presumptive Class B(WW1) uses was based on data collected in 2000 and 2005 as part of the IDNR/UHL stream biocriteria project.   A series of biological metrics that 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 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 2000 FIBI score was 73 (good) and the BMIBI score was 75 (good).   The 2005 FIBI score was 70 (good) and the BMIBI score was 79 (excellent).   This segment passed the FIBI BIC 2/2 times and passed the BMIBI BIC 2/2 times in the last ten years.   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 from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 52 and the BMIBI BIC for this ecoregion is 61.

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 between 2004 and 2008 to be considered “monitored”.   This segment had multiple samples collected in the previous 10 years (1999-2008); however, the samples were not collected during 2004-2008.   However, despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.