Assessment Comments
Assessment remains based on: (1) the results of monitoring for indicator bacteria conducted at Site 16 of the Upper Iowa River Watershed (UIRW) project from April 2004 through October 2006 and (2) result of IDNR/UHL biological (biocriteria) monitoring in 2005. EPA approval of Class A3 UAA recommendation moves the bacterial impairment to Category 5a of Iowa's Integrated Report.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(CW) 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), and due to the completion of a Use Attainability Analysis, this segment is also now designated for Class A3 (children’s contact recreation) and for Class A2 (secondary contact recreation) uses. This segment remains designated for coldwater aquatic life use (now termed Class B(CW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses)).]
SUMMARY: The Class A3 (children’s contact recreation) uses are assessed (monitored) as “not supported” due to levels of indicator bacteria that exceed state water quality criteria. The Class A2 (secondary contact recreation) uses, however, remain assessed (monitored) as “fully supported.” The Class B(CW1) coldwater aquatic life uses remain assessed (evaluated) as “fully supporting” based on biological monitoring in 1997 and 1998. Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this stream segment. The sources of data for this assessment include (1) the results of monitoring for indicator bacteria conducted at Site 16 of the Upper Iowa River Watershed (UIRW) project (STORET No. NEIARCD 191910009) from April 2004 through October 2006 and (2) result of IDNR/UHL biological (biocriteria) monitoring in 2005.
EXPLANATION: The Class A3 (children’s contact recreation) uses are assessed (monitored) as impaired due to violations of Iowa’s water quality criteria for indicator bacteria. The Class A2 (secondary contact recreation) uses, however, remain assessed (monitored) as “fully supported. The geometric mean of E. coli in the 24 samples collected at UIRW site 16 during the recreational seasons of 2004 through 2006 was 370 orgs/100 ml. This geometric mean exceeds the Class A3 criterion of 126 orgs/100 ml but is below the Class A2 criterion of 630 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). According to IDNR’s assessment/listing methodology, the results from UIRW site 16 suggest that the geometric mean exceeds the Class A3 criterion; thus, the Class A3 uses should be assessed as “not supported.” In terms of Class A2 criteria, however, the geometric mean meets the Class A2 criteria; thus, these results suggest that the Class A2 uses should be assessed as “fully supported.”
The Class B(CW1) coldwater aquatic life uses are assessed (evaluated) as "fully supported" based on results of biological monitoring. The assessment of the Class B(CW1) aquatic life uses was based on data collected in 2005 as part of the IDNR/UHL stream biocriteria project. A series of eight (8) coldwater biological indicators, which reflect stream water quality and habitat integrity, were calculated from the biocriteria sampling data and supplemental IDNR Fisheries Bureau data. The coldwater biological indicators are based on the numbers and types of coldwater benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach. Sites that score 5-8 are Fully Supporting (FS), sites that score 2-4 are Partially Supporting (PS), and sites that score 0-1 are Not Supporting (NS). The 2005 coldwater biological indicator score 5/8. The aquatic life use support was assessed (monitored) as fully supporting (=FS), based on a comparison of the coldwater biological indicator score with biological assessment criteria established for this Section 305(b) report. The coldwater biological indicators were determined from a statistical analysis of data collected at coldwater stream ecoregion reference sites from 1994-2008 and with assistance from the IDNR Fisheries Bureau.
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 a single sample collected in 2005. Despite this change in assessment methodology and type, this waterbody remains in IR Category 5a based on the bacteria data.
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream segment.
