Assessment Comments
Assessment based on 2007, 2011, 2012 and 2013 IDNR/SHL biological sampling data: FIBI = 42 (fair) and 57, 59, 61, 64 (good); BMIBI = 49, 50, 53 (fair) and 57, 61 (good). FIBI BIC = 36, BMIBI BIC = 51.
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 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" (IR 3a)due to the lack of information upon which to base an assessment. The Class B(WW2) aquatic life uses are assessed (evaluated) as "fully supported" based on results of IDNR/SHL biological sampling in 2007 and 2011-2013. Although the results of the biological sampling suggest (evaluated) "full support" of the aquatic life uses, this segment remains in IR Category 5b-t because the assessment used: (1) data older than five years (2007) and (2) data collected outside the index period (7/15-10/15).
EXPLANATION: The Class B(WW2) aquatic life uses are assessed (evaluated) as “fully supported” was based on data collected in 2007 and 2011-2013 as part of the IDNR/SHL stream biocriteria and follow-up sampling projects. 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 2007 FIBI scores were 42 (fair) and 61 (good) and the BMIBI scores were 53 (fair) and 61 (good). The 2011 FIBI score was 57 (good) and the BMIBI score was 49 (fair). The 2012 FIBI score was 59 (good) and the BMIBI score was 50 (fair). The 2013 FIBI score was 64 (good) and the BMIBI score 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 biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51. This segment passed the FIBI BIC 5/5 times and passed the BMIBI BIC 3/5 times in the last seven years.
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”. This segment had multiple samples collected in the previous five years (2009-2013); however, the data were inconclusive and could not complete the assessment. To complete the assessment, data older than five years were used; therefore, the assessment was changed from "monitored" to "evaluated." Despite this change in assessment methodology and type, this waterbody remained on Iowa’s 2010 Section 303(d) list and remains on the 2012 list of impaired waters as a fully supporting - evaluated waterbody.
