Assessment Comments
Assessment is based on: (1) the results of monitoring for indicator bacteria conducted at Site 23 of the Upper Iowa River Watershed (UIRW) project from April 2004 through October 2006 and (2) results of the fish kill investigation near Highlandville in 1999.
Basis for Assessment
[Note: Prior to the current (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). This stream segment also remains identified as an “HQ” (high quality) water.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses and the presumptive Class A2 (secondary contact recreation) uses are assessed (monitored) as “fully supported.” The Class B(CW1) coldwater aquatic life uses remain assessed (evaluated) as "partially supported” due to a fish kill in 1999. The coldwater aquatic life uses were assessed as "partially supported" for the 2000 through 2004 assessment cycles due to occurrence of a fish kill near Highlandville in 1999. Due to the absence of kills in at least three years following this kill, this assessment segment will be considered “evaluated.” Due to EPA uncertainty regarding the full recovery of the aquatic life in this stream subsequent to the kill, this stream segment remained on Iowa’s 2006 Section 303(d) list and will remain on the 2008 list (IR Category 5b). 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 are (1) the results of monitoring for indicator bacteria conducted at Site 23 of the Upper Iowa River Watershed (UIRW) project from April 2004 through October 2006 and (2) results of the fish kill investigation near Highlandville in 1999.
EXPLANATION: The presumptive Class A1 (primary contact recreation) uses and the presumptive Class A2 (secondary contact recreation) uses are both assessed (monitored) as “fully supported.” Due to recent changes in Iowa’s Water Quality Standards, Iowa’s assessment methodology for indicator bacteria has changed. Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A1 criterion for indicator bacteria (fecal coliforms) designed to protect primary contact recreation uses: the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) did not apply "when the waters [were] materially affected by surface runoff." Due to a change in the Standards in July 2003, E. coli is now the indicator bacterium, and the high flow exemption was eliminated and replaced with language stating that the Class A criteria for E. coli apply when Class A1, A2, or A3 uses “can reasonably be expected to occur.” Because the IDNR Technical Advisory Committee on WQ Standards could not agree on what flow conditions would define periods when uses would not be reasonably expected to occur, all monitoring data generated for E. coli during the assessment period, regardless of flow conditions during sample collection, will be considered for determining support of Class A uses for purposes of Section 305(b) assessments and Section 303(d) listings.
The geometric mean of E. coli in the 19 samples collected at UIRW site 23 during the recreational seasons of 2004 through 2006 was 89 orgs/100 ml. This geometric mean is below the Class A1 criterion of 126 orgs/100 ml and is far below the Class A2 criterion of 630 orgs/100 ml. Four of the 19 samples (21%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml.; 1 of the 19 samples (5%) exceeded Iowa’s Class A2 single-sample maximum criterion (2,880 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 below the applicable state criterion, the primary contact recreation uses should be assessed as "fully supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b). Also, according to U.S. EPA guidelines for Section 305(b) reporting, if less than 10% of samples exceed the single-sample maximum criterion, the primary contact recreation uses should be assessed as "fully supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b). According to IDNR’s assessment/listing methodology, the results from UIRW site 23 do not indicate that significantly greater than 10% of the samples exceed either the Class A1 or Class A2 single-sample maximum criterions. Thus, these results suggest that both the Class A1 and Class A2 uses should be assessed as “fully supported.”
The Class B(CW) coldwater aquatic life uses remain assessed (evaluated) as "partially supported.” These uses were assessed as "partially supported" for the 2000 through 2004 assessment cycles due to occurrence of a fish kill on August 5, 1999 northwest of Highlandville in Winneshiek County. As stated in the assessment developed for the 2000 report, the kill followed a 2-3 inch rainfall event; no other water quality problems were observed. An estimated 3,200 fish were killed. No responsible party for the kill was identified. According to IDNR’s assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period (2004-2007) indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired.” If a cause of the kill is identified, and the cause is either known, or suspected, to be a “pollutant”, the assessment type is considered “monitored” and the affected waterbody is a candidate for Section 303(d) listing. Fish kills attributed to a pollutant, but where a source of the pollutant was not identified and/or where enforcement actions were not taken against the responsible party, will be placed into Integrated Report subcategory 5b. The intent of placing these waterbodies into Category 5 is not to necessarily require a TMDL but to keep the impairment highlighted due to the potential for similar future kills from the unaddressed causes and/or sources. For its draft 2006 assessment, IDNR considered this stream segment to be “not assessed” (IR Category 3a) and was proposed for removal from Iowa’s 2006 Section 303(d) list. According to IDNR’s assessment/listing methodology, if the most recent pollution-caused fish kill occurred on this stream segment more than six years ago (i.e., before the 2000-2005 period), any toxic impacts associated with the kill are assumed to have dissipated, and the affected water would be considered “not assessed.” Due, however, to EPA uncertainty regarding the full recovery of the aquatic life in this stream subsequent to the kill, this stream segment remained on Iowa’s 2006 Section 303(d) list (IR Category 5b) and will be placed on Iowa’s 2008 list.
Fish consumption uses are not assessed due to the lack of fish contaminant monitoring in this stream reach.
