Assessment Comments
Assessment is based on results of IDNR/UHL biological (biocriteria) monitoring in 2003: FIBI = 34 (fair), 33 (fair); BMIBI = 33 (fair), 45 (fair). FIBI BIC = 32 (non-riffle), 53 (riffle); BMIBI BIC = 62.
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/EXPLANATION: The presumptive Class A1 (primary contact recreation) uses are "not assessed" due to the lack of information upon which to base an assessment
The assessment of the Class B(WW2) aquatic life uses was based on data collected in 2003 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 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 FIBI scores were 34 (fair); 33 (fair) and the BMIBI scores were 33 (fair); 45 (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 FIBI BIC for this ecoregion is 32 (non-riffle) and 53 (riffle) and the BMIBI BIC for this ecoregion is 62. The 34 FIBI score corresponds with a non-riffle site and passed the non-riffle BIC (32), while the 33 FIBI score was from a riffle site, thus it failed to meet the riffle BIC (53). In addition, both sites failed to meet the BMIBI BIC of 62.
