Assessment Comments
Assessment is based on results of 1994-1997 and 2000 IDNR/UHL biological monitoring data: FIBI = 47, 48 (fair), 52, 57, 59, 61 (good); BMIBI = 58, 62, 67, 71, 62 (good). Riffle habitat FIBI BIC = 53, BMIBI BIC = 62.
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 (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.]
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 Class B(WW-2) aquatic life uses are assessed (evaluated) as "fully supported" based on results of IDNR/UHL biological (biocriteria) sampling in 1994-1997 and 2000. The biological sampling data are now more than five years old; therefore, this assessment is considered evaluated (less confidence) instead of monitored.
EXPLANATION: The Class B(WW2) aquatic life uses remain assessed (evaluated) as “fully supporting” based on biological data collected in 1994-1997 and 2000 as part of the IDNR/UHL stream biocriteria project. The 1994-1997 and 2000 FIBI scores were 47, 48 (fair), 52, 57, 59, 61 (good). The 1994-1997 and 2000 BMIBI scores were 58, 62, 67, 71, 62 (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 riffle habitat FIBI BIC for this ecoregion is 53 and the BMIBI BIC for this ecoregion is 62. This segment passed the FIBI BIC 3/6 times and passed the BMIBI BIC 4/5 times in the past 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. Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). Despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.
