Assessment Comments
Assessment based on 2004, 2005 & 2012 IDNR/SHL biological sampling data: 2004 FIBI = 64 (good), 36 (fair), 2004 BMIBI = 36 (fair), 36 (fair); 2005 FIBI = 54 (good), 2005 BMIBI = 20 (poor); 2012 FIBI = 31 (fair), 2012 BMIBI = 40 (fair). 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(WW) aquatic life uses, including fish consumption uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, this segment is also now presumptively designated for Class A1 (primary contact recreation) uses. This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]
SUMMARY/EXPLANATION: The presumptive Class A1 (primary contact recreation) and Class HH (human health/fish consumption uses) uses remain "not assessed" (IR 3a) due to the lack of information upon which to base an assessment.
The Class B(WW1) aquatic life uses remains assessed (evaluated) as “partially supporting” (IR 5b-v) based on data collected in 2004, 2005 and 2012 as part of the IDNR/SHL 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 2004 FIBI scores were 64 (good), 36 (fair) and 2005 FIBI score was 54 (good). The 2004 BMIBI score was 36 (fair), 36 (fair) and 2005 BMIBI score was 20 (poor). The 2012 FIBI score was 31 (fair) and the 2012 BMIBI score was 40 (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 1994-2008. The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51. This segment passed the FIBI BIC 3/4 times and passed the BMIBI BIC 0/4 times in the last nine years.
For previous assessments, the aquatic life use assessment was considered "monitored" because there were two or more samples collected in multiple years in a five year period. Because, however, these data have aged beyond five years, the assessment type is now considered “evaluated” (lower confidence) as opposed to “monitored” (higher confidence). Despite this change in assessment type, this waterbody was previously on Iowa’s Section 303(d) list and thus remains on Iowa’s Section 303(d) list of impaired waters (IR Category 5b-v).
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this assessment segment.
