Assessment Comments
Assessment remains based on: (1) the results of monitoring for indicator bacteria conducted at Site 19 of the Upper Iowa River Watershed (UIRW) project from April 2004 through October 2006, (2) results of IDNR/UHL biological (biocriteria) monitoring in 1999 and (3) an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in May 2006.
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), this segment is also now presumptively designated for Class A1 (primary contact recreation) and 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 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 presumptive 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 1999. 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 19 of the Upper Iowa River Watershed (UIRW) project (STORET No. NEIARCD 191910012) from April 2004 through October 2006, (2) results of IDNR/UHL biological (biocriteria) monitoring in 1999 and (3) an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in May 2006.
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 presumptive Class A2 (secondary contact recreation) uses, however, remain assessed (monitored) as “fully supported.” The geometric mean of E. coli in the 22 samples collected at UIRW site 19 during the recreational seasons of 2004 through 2006 was 427 orgs/100 ml. This geometric mean far exceeds the Class A1 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 19 suggest that the geometric mean exceeds the Class A1 criterion; thus, the Class A1 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 remain assessed (evaluated) as “fully supporting.” The assessment of the coldwater aquatic life uses was based on data collected in 1999 as part of the DNR/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 1999 coldwater biological indicator score was 7/8. The aquatic life use support was assessed 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 1999. 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).
In addition, based on an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in May 2006, the Class B(CW1) uses are assessed as "fully supported". According to the updated summary, Coon Creek is in the group of Iowa coldwater streams that supports natural reproduction of trout. Based on results of surveys by the IDNR Fisheries Bureau, this stream is placed in the category of Iowa trout streams that exhibit recent, but inconsistent reproductive success and that are generally not capable of maintaining a viable population for the resident trout species at this time. This assessment is consistent with previous assessments of the ability of this stream to support natural reproduction of trout.
Fish consumption uses remain "not assessed" due to lack of fish tissue monitoring in this stream segment.
