Assessment Comments
Assessment is based on 1994-1997, 2000 and 2007 IDNR/UHL biological monitoring data: FIBI = 41, 40, 35, 34, 47, 31, 47 (fair), BMIBI = 54 (fair), 73, 71, 73, 68, 65 (good), 78 (excellent). FIBI BIC = 36, BMIBI BIC = 51.
Basis for Assessment
Note 1: 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 (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 (2010) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
[Note 2: Although USGS monitoring was conducted in this segment during the 2004-2006 assessment period, only one sample was collected and analyzed. This sample, collected on October 5, 2004, did not violate the respective Class B(WW2) criteria for ammonia, dissolved oxygen, or pH. This amount of data is insufficient for developing an updated assessment of support of designated uses. Thus, the assessment developed for the previous (2006) assessment cycle will be used for the current (2008) cycle.]
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 remain assessed (evaluated) as "fully supported" based on results of IDNR/UHL biological (biocriteria) sampling in July 2000.
EXPLANATION: This assessment of the Class B(WW2) aquatic life used was based on data collected in 1994-1997, 2000 and 2007 as part of the IDNR/UHL stream biocriteria project. The FIBI scores were 41, 40, 35, 34, 47, 31, 47 (all fair) and the BMIBI scores were 54 (fair), 73, 71, 73, 68, 65 (good), 78 (excellent). The aquatic life use support was assessed 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 1994-2004. The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51. This segment passed the FIBI BIC 4/7 times and passed the BMIBI BIC 7/7 times in the last 15 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 between 2004 and 2008 to be considered “monitored”. This segment had multiple samples collected in the previous 15 years (1994-2008); however, the multiple samples were not collected during 2004-2008. Despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.
