Assessment Comments
Assessment based on 2000, 2006 and 2012 IDNR/SHL biological sampling data: FIBI = 23 (poor), 27, 32 (both fair); BMIBI = 45, 45, 55 (all fair). Non-riffle habitat FIBI BIC = 32, 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, 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 aquatic life uses are assessed (evaluated) as "partially supported" (IR 5b-t) based on results of IDNR/SHL biological (biocriteria) sampling in 2000, 2006 and 2012.
EXPLANATION: The Class B(WW2) aquatic life uses are assessed (evaluated) as “partially supported” based on data collected in 2000, 2006 and 2012 as part of the IDNR/SHL stream biocriteria project. The 2000 FIBI score was 27 (fair) and the BMIBI score was 55 (fair). The 2006 FIBI score was 32 (fair) and the BMIBI score was 45 (fair). The 2012 FIBI score was 23 (poor) and the BMIBI score was 45 (fair). The aquatic life use support assessment was assessed as partially supporting (=PS), 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 non-riffle habitat FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62. This segment passed the FIBI BIC 1/3 times and passed the BMIBI BIC 0/3 times in the past 13 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 13 years (2000-2012); however, the multiple samples were not collected during a five-year period. According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation). However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5b-t and remains on Iowa’s Section 303(d) list of impaired waters.
