Assessment Comments
Assessment is based on: (1) the results of monitoring for indicator bacteria conducted at Site 20 of the Upper Iowa River Watershed (UIRW) project from April 2004 through October 2006 and (2) results of IDNR/UHL biological (biocriteria) monitoring in 1997 & 2003.
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. 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 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: The presumptive Class A1 (primary contact recreation) uses remain assessed (monitored) as “not supported” due to levels of indicator bacteria that exceed state water quality criteria. The Class B(WW1) aquatic life uses remain assessed (monitored) as “fully supported” based on results of biological monitoring in 1997 & 2003. Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this assessment segment. The sources of data for this assessment include (1) the results of monitoring for indicator bacteria conducted at Site 20 of the Upper Iowa River Watershed (UIRW) project (STORET No. NEIARCD 191910013) from April 2004 through October 2006 and (2) results of IDNR/UHL biological (biocriteria) monitoring in 1997 & 2003.
EXPLANATION: The presumptive Class A1 (primary contact recreation) uses remain assessed (monitored) as “not supported” due to violations of Iowa’s water quality criteria for indicator bacteria. The geometric mean of E. coli in the 22 samples collected at UIRW site 20 during the recreational seasons of 2004 through 2006 was 198 orgs/100 ml. This geometric mean exceeds the Class A1 criterion of 126 orgs/100 ml. Ten of the 22 samples (45%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean of E. coli is greater than the applicable state criterion, the primary contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b).
The Class B(WW1) aquatic life uses remain assessed (monitored) as “fully supported.” This assessment remains based on data collected in 1997 and 2003 as part of the IDNR/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 1997 FIBI score was 81 (excellent) and the BMIBI score was 80 (excellent). The 2003 FIBI score was 77 (excellent) and the BMIBI score was 81 (excellent). 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 1994-2004. The FIBI BIC for this ecoregion is 52 and the BMIBI BIC for this ecoregion is 61. This segment passed the FIBI and BMIBI BICs 2/2 times in the last 12 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 between 2004 and 2008 to be considered “monitored”. This segment had multiple samples collected in the previous 12 years (1997-2008); however, the multiple samples were not collected during 2004-2008. Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).
Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this assessment segment.
