Assessment Comments
Current assessment is based on results of IDNR/UHL biological (biocriteria) monitoring in 2005: FIBI = 30 (fair) and data were insufficient to calculate a BMIBI. Non-riffle habitat FIBI BIC = 32; BMIBI BIC = 62. However, biological monitoring in 2000 yielded a FIBI average of 34 and a BMIBI average of 38.5.
Basis for Assessment
[Note: Prior to the current (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), and due to the completion of a Use Attainability Analysis in 2007, this segment is now 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 (2008) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY: The Class A1 (primary contact recreation) uses are "not assessed" due to the lack of information upon which to base an assessment. The Class B(WW-2) aquatic life uses continue to be assessed (monitored) as "partially supported" based on results of IDNR/UHL biological (biocriteria) sampling in 2005. Following strict protocol and applying the Uncertainty Adjustment Value (UAV) of 7 points to just the 2005 FIBI sample and ignoring data five years old or older, this site would be fully supporting. However, because insufficient data were collected to calculate a 2005 BMIBI score and given the history of low BMIBI values from this location, this segment remains partially supporting. This is the same assessment as that developed for the 2006 reporting cycle.
EXPLANATION: The assessment of the Class B(WW2) aquatic life uses was based on data collected at two sites in 2000 and one site in 2005 as part of the DNR/UHL stream biocriteria project. A series of biological metrics which 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 that were 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 average was 34 (fair) and the 2000 BMIBI average was 38.5 (fair). The 2005 FIBI score was 30 (fair). The aquatic life use support 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 1994-2004. The non-riffle habitat FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62.
