Assessment Comments
Assessment is based on: (1) results of IDNR/SHL TMDL monitoring in 2009 at Yellow River Main Stem 1 near Hwy 52 crossing, (2) results of IDNR/SHL chemical/physical/bacterial water quality monitoring conducted from 2004-06 at station 15030003, (3) results of an investigation of a fish kill that occurred in March 2000, and (3) results of IDNR/SHL biological monitoring in 2000 and 2004.
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, 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 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 remain assessed (monitored) as "not supported" due to violations of water quality criterion for dissolved oxygen. Fish consumption uses remain “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/SHL TMDL monitoring at Yellow River Main Stem 1 (Station 11030001 near Hwy 52 crossing, Allamakee County) from mid-July to mid-September 2009, (2) results of IDNR/SHL 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), (3) results of IDNR/SHL bacteria monitoring conducted from January 2006 through September 2008 as part of the Yellow River watershed project at the County Road W60 crossing (station 15030003), (4) results of an investigation of a fish kill that occurred in March 2000, and (5) results of IDNR/SHL biological monitoring in 2000 and 2004.
Note: A TMDL for the bacterial impairment for streams in the Yellow River basin was prepared by Iowa DNR in 2012 and was approved by U.S. EPA in February 2013 (see http://www.iowadnr.gov/Environment/WaterQuality/WatershedImprovement/WatershedResearchData/WaterImprovementPlans/PublicMeetingsPlans.aspx). Due to completion of the TMDL, the Integrated Report categories for the Class A1 and Class A2 recreational uses are changed from 5p (impaired; TMDL needed) to 4a (impaired; TMDL approved). Because not all impairments identified for this assessment segment are covered by the TMDL (aquatic life impairment due to low dissolved oxygen), this segment remains in Category 5a of Iowa's 2012 Integrated Report (impaired and TMDL required).
EXPLANATION: Both the Class A1 (primary contact recreation) and Class A2 (secondary contact recreation) uses are 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 13 samples collected at IDNR/UHL station 11030001 during the recreational season of 2009 was 13,288 orgs/100 ml. This geometric mean far exceeds the Class A1 criterion of 126 orgs/100 ml. All 13 samples (100%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml. This geometric mean also far exceeded the Class A2 criterion of 630 orgs/100 ml. Nine of the 13 samples (69%) 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 recreation season geometric mean for IDNR/SHL station 11030001 exceeds both the Class A1 and Class A2 criteria, these uses are assessed as “not supported.”
Although more recent (2009) monitoring shows improvement in water quality, the Class B(CW1) coldwater aquatic life uses remain assessed (monitored) as “not supported.” The results of the IDNR/SHL water quality monitoring from May 2004 through November 2006 showed 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. Only one of the 8 samples (12%) collected from July to September 2009 violated the Class B(CW1) criterion of 7.0 mg/l: the sample collected on August 9, 2009 contained 6.8 mg/l of dissolved oxygen. According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17), a violation frequency of greater than 10% for conventional parameters such as pH and dissolved oxygen suggests impairment of aquatic life uses. Based on IDNR’s assessment methodology, however, these results suggest that the frequency of violations is not significantly greater than10 percent; thus, these results do not suggest impairment of the Class B(WW2) aquatic life uses. Because, however, an aquatic life impairment due to low dissolved oxygen was identified for the previous (2010) assessment listing cycle, and because the frequency of violations during the current (2012) cycle approaches the impairment level, the Class B(WW2) aquatic life uses of this assessment segment will remain assessed as Section 303(d)-impaired due to low dissolved oxygen. If the frequency of violations of the dissolved oxygen criterion continues to decline, this impairment may be de-listed for a future listing cycle.
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 Road 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 3,000 and 5,000 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 five 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 based on data collected in 2000 and 2004 as part of the IDNR/SHL coldwater stream sampling projects. A series of biological metrics which reflect coldwater stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa that were collected in the stream sampling reach. The biological metrics were combined to make a coldwater benthic index (CBI). The index ranks the biological integrity of a coldwater stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2000 CBI scores were 44, 48 and 48. The 2004 CBI score was 35. The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the CBI scores with biological impairment criteria (BIC) established for the 2012 Section 305(b) report. The biological impairment criteria were determined from a statistical analysis of data collected at coldwater stream reference sites from 1994-2011. The CW BIC is 60 and this segment passed the CW BIC 0/4 times in a five-year period (2000-2004).
This aquatic life assessment would be considered "monitored" 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 over a five-year period to be considered “monitored”. This segment had multiple samples collected in a five-year period (2000-2004); however, the data are now more than five years old and are no longer for monitored assessments, only evaluated assessments. According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation). However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5a and remains on Iowa’s Section 303(d) list of impaired waters.
Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this stream segment.
