Assessment Comments
Assessment remains based on results of (1) IDNR/UHL biocriteria sampling in 1998 & 2004, (2) U.S. EPA/IDNR fish tissue (RAFT) monitoring at Pammell Park in 2002, and (3) a report of a fish kill in July 2002.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this river segment was designated only for Class B(WW) aquatic life uses, including fish consumption uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008 and due to the completion of a Use Attainability Analysis in 2007, this segment is also now designated for Class A1 (primary contact recreation) uses. This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]
SUMMARY: The Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment. The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported” based on results of biological monitoring in 1998 and 2004. Fish consumption uses are assessed (evaluated) as "fully supported" based on results of fish contaminant monitoring in 2002. Sources of data for this assessment include (1) results of IDNR/UHL biological monitoring conducted in 1998 and 2004 as part of the stream biocriteria project, (2) a report of a fish kill on July 20, 2002, and (3) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2002.
EXPLANATION: The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported” based on results of IDNR/UHL biological monitoring conducted on this stream segment in 1998 and 2004. The 1998 FIBI score was 38 (fair) and the BMIBI score was 61 (good). The 2004 FIBI score was 32 (fair) and the BMIBI score was 53 (fair). The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51. This segment passed the FIBI BIC 1/2 times and passed the BMIBI BIC 2/2 times in the last 13 years.
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 over a five-year period to be considered “monitored”. This segment had multiple samples collected in the previous 13 years (1998-2010); however, the multiple samples were not collected during a five-year period. 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).
A fish kill occurred in this river segment on July 20, 2002 near the Middle River Park south of Winterset. This kill is believed due to warm water temperatures, low river flow, and the die-off of an algae bloom that reduced levels of dissolved oxygen below that needed to sustain large fish. At the time of the kill, levels of dissolved oxygen were in the vicinity of 3 mg/l; the water was brownish, probably due to the senescence of the algal bloom. Because this kill is largely due to natural causes (low flow; high water temperatures), the kill does not influence the assessment of support of the designated aquatic life uses of this stream segment.
Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring southwest of Winterset in 2002. The composite samples of fillets from channel catfish and walleye had low levels of contaminants. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.142 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of walleye fillets were as follows: mercury: 0.184 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm.
The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses. Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa. In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol. This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol). Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses. This scenario, however, does not apply to the fish contaminant data generated from the 2002 RAFT sampling conducted in this assessment segment: the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.
