Assessment Comments
Assessment remains based on 1997, 2005 and 2006 IDNR/UHL biological monitoring data: 2005 FIBI = 49 (fair), 2006 FIBI = 40 (fair); 1997 BMIBI = 75 (good), 2006 BMIBI = 57 (good). Non-riffle 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 (2012) 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(WW2) aquatic life uses remain assessed (evaluated) as "partially supported" based on results of biological monitoring conducted in 1997, 2005 and 2006 as part of the IDNR/UHL biocriteria and REMAP projects.
EXPLANATION: The Class B(WW2) aquatic life uses are assessed (evaluated) as “partially supported” based on data collected in 1997, 2005 and 2006 as part of the IDNR/UHL stream biocriteria and REMAP projects. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biological 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 1997 BMIBI score was 75 (good). The 2005 FIBI was 49 (fair) and the 2006 FIBI was 40 (fair). The 2006 BMIBI was 57 (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 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 2/2 times in the last five years and passed the BMIBI BIC 1/2 times in the past 14 years. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.
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”. However, this segment did not have multiple BMIBI samples between 2006-2010; thus, this assessment is considered evaluated. 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).
