Assessment Comments
Assessment based on 2008 and 2009 IDNR/SHL biological sampling data: FIBI = 26, 29 (fair) and BMIBI = 26 (poor) and 46 (fair). FIBI BIC = 33, BMIBI BIC = 41.
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 assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY/EXPLANATION: 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 Class B(WW2) aquatic life uses are assessed (monitored) as “partially supporting” (impaired), and this waterbody remains in Category 5b-v of Iowa’s Integrated Report.
The assessment of the Class B(WW2) aquatic life uses was based on data collected in 2008 and 2009 by IDNR/SHL in support of SI/TMDL development. 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 2008 FIBI score was 26 (fair) and the 2008 BMIBI score was 26 (poor). The 2009 FIBI score was 29 (fair) and the 2009 BMIBI score was 46 (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 from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The FIBI BIC for this ecoregion is 33 and the BMIBI BIC is 41. This segment passed the BIBI BIC 0/2 times and passed the BMIBI BIC 1/2 times in the last five years.
This assessment is considered "monitored" because there were multiple samples collected in multiple years during a recent five year period from this segment.
