Assessment Comments
Assessment based on 2003 REMAP data: FIBI = 50 (fair), 49 (fair); BMIBI = 46 (fair), 42 (fair) and 2003 Biocriteria data: FIBI = 60 (good); BMIBI = 78 (excellent). Riffle habitat FIBI BIC = 65, non-riffle habitat FIBI BIC = 44; natural substrate BMIBI BIC = 70.
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), 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 (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 presumptive Class A1 (primary contact recreation) uses are "not assessed" due to the lack of information upon which to base an assessment. This segment is partially supporting its Class B(WW2) aquatic life uses because the BMIBI scores from the REMAP site failed to meet the BMIBI BIC for this ecoregion and sample type. All of the FIBI scores and the BMIBI score from the biocriteria site met the applicable BICs.
EXPLANATION: The assessment of the Class B(WW2) aquatic life uses was based on data collected in 2003 as part of the DNR/UHL stream REMAP and biocriteria 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 2003 biocritera riffle habitat FIBI score was 60 (good) and the benthic macroinvertebrate hess sample (natural substrate) BMIBI score was 78 (excellent). The 2003 REMAP non-riffle habitat FIBI scores were 50 (fair); 49 (fair) and the 2003 benthic macroinvertebrate hess sample BMIBI scores were 46 (fair) and 42 (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 riffle habitat FIBI BIC for this ecoregion is 65 and the non-riffle habitat FIBI BIC is 44. The hess sample/natural substrate BMIBI BIC for this ecoregion is 70.
