Assessment Comments
Assessment is based on: (1) results of IDNR/UHL chemical/physical water quality monitoring conducted from May 2004 through November 2006 as part of the Yellow River watershed project at the County Road W60 crossing (station 15030003), (2) results of an investigation of a fish kill that occurred in March 2000, and (3) results of IDNR/UHL biological monitoring in September 2004.
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 “HQR” (high quality resource) water.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses and the presumptive Class A2 (secondary contact recreation) uses are both assessed (monitored) as “not supported” due to levels of indicator bacteria that exceed state water quality criteria. The Class B(CW1) aquatic life uses are assessed (monitored) as "not supported" due to violations of water quality criterion for dissolved oxygen. Fish consumption uses were “not assessed” due to the lack of fish contaminant monitoring in this stream segment. Sources of data for this assessment include (1) results of IDNR/UHL chemical/physical water quality monitoring conducted from May 2004 through November 2006 as part of the Yellow River watershed project at the County Road W60 crossing (station 15030003), (2) results of an investigation of a fish kill that occurred in March 2000, and (3) results of IDNR/UHL biological monitoring in September 2004.
EXPLANATION: Both the Class A1 (primary contact recreation) and Class A2 (secondary contact recreation) uses were assessed (monitored) as “not supported” due to violations of Iowa’s water quality criteria for indicator bacteria. 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 70 samples collected at IDNR/UHL station 15030003 during the recreational seasons of 2004 through 2006 was 1,616 orgs/100 ml. This geometric mean far exceeds the Class A1 criterion of 126 orgs/100 ml. Sixty-two of the 70 samples (89%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml. The geometric mean of the 79 samples collected at this station during calendar years of 2004 through 2006 was 1,190; this geometric mean exceeds the Class A2 criterion of 630 orgs/100 ml. Twenty of the 79 samples (25%) 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 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). Thus, because the geometric means for IDNR/UHL station 15030003 exceeds both the Class A1 and Class A2 criteria, these uses are assessed as “not supported.”
The Class B(CW1) coldwater aquatic life uses are assessed (monitored) as “not supported.” The results of the IDNR/UHL water quality monitoring from May 2004 through November 2006 show 37 violations of the Class B(CW1) criteria for dissolved oxygen (7.0 mg/l) in the 80 samples (46%) collected. The violations were relatively minor with a minimum dissolved oxygen value of 4.9 mg/l in the 80 samples collected. According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), "nonsupport" of aquatic life uses is indicated if criteria are exceeded in more than 25% of the samples for conventional parameters (e.g., pH, temperature, or dissolved oxygen). Thus, the percentages of violations of the dissolved oxygen criterion in this stream segment (46%) suggests an impairment of coldwater aquatic life uses.
A fish kill occurred on this stream reach on March 17, 2000. An estimated 4,800 fish were killed; no cause or source of the kill was identified. The following account is from the IDNR fish kill database and includes comments from the IDNR staff that investigated the kill: "Dead fish were observed both upstream and downstream of the Smith Rd. bridge on the Yellow River, but only below the confluence with the unnamed tributary in section 17. North of Postville. Water turbid and green, with high flow. The kill affected a 3.1 mile segment of the Yellow River. Dead fish were not observed in the unnamed trib that enters into the Yellow River in Sec. 17. A total of 12 species of fish were affected. After visually inspecting the habitat in the area that the fish kill occurred, we would rate the habitat as excellent. The bottom substrate of much of the stream is composed of gravel and cobble. Deeper water areas for fish overwintering locations are also available. The Smith Rd. Bridge is the upstream extent of the area in which we have stocked fingerling brown and rainbow trout. No trout were seen in any of the counts of dead fish. The total number of fish that were observed was very low for a stream of this size and habitat quality. In previous work by Paragamian (1986), between 3000 and 5000 fish/acre were seen in northeast Iowa streams of comparable sizes. We feel that there has been an unknown factor at work that has severely reduced the total fish community in this section of the Yellow River prior to the total kill that this incident has caused to occur."
According to DNR's assessment methodology for Section 305(b) reporting, because this fish kill occurred more than three years ago, this kill indicates that the aquatic life uses should be assessed (evaluated) as "partially supported". "Evaluated" assessments are of lesser confidence than are "monitored" assessments and are thus not appropriate for justifying addition of a waterbody to Category 5 of the Integrated Report (=the Section 303(d) list). This type of assessment is, however, appropriate for Categories 2b or 3b of Iowa's Integrated Report that comprise Iowa's list of waters in need of further investigation.
The assessment of the Class B(CW1) aquatic life uses was also based on data collected in 2004 as part of the DNR/UHL stream REMAP project. A series of four (4) coldwater biological indicators, which reflect stream water quality and habitat integrity, were calculated from the biocriteria sampling data. The coldwater biological indicators are based on the numbers and types of coldwater benthic macroinvertebrate taxa that were collected the stream sampling reach. Sites that do not receive any type of trout stocking are scored on the benthic macroinvertebrate data only. Non-trout stocking sites that score 3 or 4 are Fully Supporting (FS), sites that score 1 or 2 are Partially Supporting (PS), and sites that score 0 are Not Supporting (NS). The 2004 REMAP coldwater biological indicator score was 1/4. The aquatic life use support was assessed (monitored) as Partially Supporting (=PS), 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 1994-2004 and with assistance from the IDNR Fisheries Bureau.
Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this stream segment.
