Assessment Comments

Assessment is based on: (1) the results of U.S. Geological Survey chemical/physical water quality monitoring at Keosauqua from March 2004 through December 2006, (2) results of U.S. EPA/IDNR fish contaminant monitoring in 2002 and 2004 at Keosauqua, and (3) results of a fish kill investigation in July 2006.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses are "not assessed" due to the lack of water quality information upon which to base an assessment.   The Class B(WW1) aquatic life uses are assessed (monitored) as “partially supporting” based on results of a fish kill investigation in July 2006 and a history of fish kills in, and upstream from, this assessment segment.   Results of chemical/physical monitoring from 2004-2006, however, suggest "full support" of the Class B(WW1) uses.   Fish consumption uses remain assessed (monitored) as "fully supported" based on fish contaminant monitoring in 2002 and 2004.   The sources of data for this assessment are (1) the results of U.S.  Geological Survey chemical/physical water quality monitoring at Keosauqua from March 2004 through December 2006, (2) results of U.S.  EPA/IDNR fish contaminant monitoring in 2002 and 2004 at Keosauqua, (3) results of a fish kill investigations in July 2002 and July 2006.  

EXPLANATION:  The Class A1 uses were not assessed due to the lack of water quality monitoring and other water quality information for this river segment upon which to assess support of these uses (USGS monitoring in this river segment did not include analysis for indicator bacteria).   Prior to the 2002 report, these uses were assessed based on results of water quality monitoring conducted near Keokuk (see assessments for the 1998 and 2000 reports).   This monitoring station, however, is more than 30 miles downriver from the current assessment segment (IA 04-LDM-0010-3), and previous assessment likely represent an excessive extrapolation of the monitoring results from the Keokuk station.  

The Class B(WW1) aquatic life uses are assessed (monitored) as “partially supported” due to fish kills on July 31, 2002 and on July 10, 2006 on the reach of river between Eldon (Wapello Co.) and Douds (Van Buren Co.).    These recent kills are two in a series of kills that have occurred over the last ten years or so that appear to involve primarily shovelnose sturgeon (Schaphirynchus platorynchus).    Although the cause of the 2002 and 2006 kills and the previous kills remains unknown, the leading hypotheses are (1) that very high water temperatures, very low river flows, and elevated pH levels combine to make ambient levels of ammonia in the river toxic to the ammonia-intolerant shovelnose sturgeon and (2) that the kills are caused by a virus specific to shovelnose sturgeon.    

According to IDNR's assessment methodology for Section 305(b) reporting, occurrence of a single pollution-caused fish kill within the most recent three-year period (2004-2007) indicates that the aquatic life uses of a waterbody are only "partially supported."  Thus, the Class B(WW1) aquatic life uses of this river reach were assessed as "partially supported."  Also, according to IDNR’s assessment methodology, if a cause of a fishkill was not identified during the IDNR investigation (cause = "unknown"), or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated.”  Such assessments, although suitable for Section 305(b) reporting, typically lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (Category 5 of the Integrated Report).    Waterbodies affected by such fish kills at usually placed in IR subcategories 2b or 3b and are added to the state’s list of “waters in need of further investigation”.    Due however to (1) the repeated occurrence of these kills over the last 10 years in Wapello and Van Buren counties, (2) the often large numbers of sturgeon killed (thousands), (3) the likelihood that these kills are caused by a pollutant and (4) the possibility that the kills have extended further downstream (possibly to Bonaparte), this impairment is added to Iowa’s Section 303(d) list (Category 5 of the Integrated Report).   Although applied to upriver segments (e.g., IA 04-LDM-0010_4) for the previous (2006) assessment/listing cycle, this (2008) is the first cycle in which this segment (IA 04-LDM-0010_3) has been considered fishkill-impaired.    

Results of water quality monitoring by the U.S.  Geological Survey near Keosauqua from 2004 through 2006, however, suggest "full support" of the Class B(WW1) uses.   No violations of state water quality criteria occurred in the approximately 33 samples analyzed for dissolved oxygen and ammonia, DDE, and dieldrin.   Only one sample was analyzed for toxic metals during the 2004-2006 assessment period; no violations of Class B(WW1) criteria occurred in this sample.   Two of the 33 samples analyzed (6%) had pH values greater than 9.0 units with a maximum value of 9.1 units.   Violations of the high-pH criterion tend to occur on days when dissolved oxygen levels were at or above 100% saturation, and these conditions suggest that high levels of primary productivity may have resulted in the high levels of pH observed.   According to U.S.  EPA guidelines for Section 305(b) reporting (U.S.  EPA 1997b:  page 3-17), however, a violation frequency for conventional parameters (including pH) of less than 10% does not suggest an impairment of aquatic life uses.  

Results of EPA/DNR fish tissue (RAFT) trend monitoring near Keosauqua in 2002 and 2004 showed that the composite sample of whole-fish common carp collected from this site have low levels of contaminants.   This site has been sampled for whole-fish common carp since 1994 on an every-other-year basis as part of RAFT trend monitoring.   The results from the 2002 sampling show low levels of the primary contaminants (chlordane, PCBs and mercury) in the composite whole-fish sample of common carp:  mercury:  0.101 ppm; total PCBs:  0.135 ppm; and technical chlordane:  0.12 ppm.   The results from the 2004 sampling also showed low levels of the primary contaminants (chlordane, PCBs and mercury) in the composite whole-fish sample of common carp:  mercury:  0.062 ppm; total PCBs:  0.136 ppm; and technical chlordane:  0.09 ppm.  

The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes.   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 or 2004 RAFT samplings (or from previous RAFT trend monitoring) 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.