Assessment Comments
Assessment is based on: (1) results of monthly monitoring from 2004 through 2006 at the IDNR/UHL ambient city monitoring station located downstream from Fort Dodge near Kalo (STORET station 10940003) and (2) results of U.S. EPA/IDNR fish tissue (RAFT) monitoring near Dolliver State Park in 2005.
Basis for Assessment
[Note 1: Prior to the current (2008) Section 305(b) cycle, this stream 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 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), 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).]
[Note 2: This assessment was also used for the adjacent downstream segment of the Des Moines River (IA 04-UDM-0040-1).]
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on results of ambient monitoring for indicator bacteria (E. coli). The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" based on results of ambient chemical/physical monitoring from 2004-06. Fish consumption uses are assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2005. The sources of data for this assessment include (1) results of monthly monitoring from 2004 through 2006 at the IDNR/UHL ambient city monitoring station located downstream from Fort Dodge near Kalo (STORET station 10940003) and (2) results of U.S. EPA/IDNR fish tissue (RAFT) monitoring near Dolliver State Park in 2005.
EXPLANATION: The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on results of monitoring for indicator bacteria (E. coli). 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 A 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 level of indicator bacteria (E. coli) in the 24 samples collected (99 orgs/100ml) during the recreational seasons of 2004 through 2006 is below, and meets, Iowa’s Class A1 water quality criterion of 126 orgs/100ml. Five of the 24 samples (21%), however, exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting, if levels of E. coli exceed the single-sample maximum criterion in more than 10% of the samples, the primary contact recreation uses should be assessed as “partially supported” (see pgs 3-33 to 3-35of U.S. EPA 1997b). According to IDNR’s assessment/listing methodology, these results suggest that the violation frequency of Iowa’s single-sample maximum criterion in this assessment segment is, by one violation, significantly greater than 10%, and thus these results suggest an impairment of the Class A1 uses of this river segment.
Results of bacterial monitoring from 2004-2006 at IDNR/UHL station 10940003 downstream from Fort Dodge, as well as at other monitoring stations upriver from Saylorville Reservoir, suggest low levels of E. coli in the upper Des Moines River. For example, the three-year geometric means (N=24-36 samples) for stations near Boone (127 orgs/100 ml), downstream from Fort Dodge (99 orgs/100 ml), upstream from Fort Dodge (82 orgs/100 ml), and on the West Fork Des Moines River near Humboldt (103 orgs/100 ml) all met the Iowa Class A1 criterion of 126 E. coli orgs/100 ml. Although the percentage of samples greater than Iowa’s single-sample maximum criterion suggests impairment at several of these stations, the difference between impairment and “full support” is typically one sample violation. These results suggest generally low levels of indicator bacteria in the Des Moines River upriver from Saylorville Reservoir.
The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported." Ambient chemical/physical monitoring conducted at the IDNR city station from 2004-2006 showed no violations of Class B(WW1) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen in the 36 samples collected, for toxic metals (including mercury) in the 14 samples collected, and for pesticides in the seven samples analyzed. These results suggest that the Class B(WW1) uses should be assessed as "fully supported."
This segment of the Des Moines River was sampled as part of the 1998-99 statewide study of freshwater mussels in Iowa streams and rivers (Arbuckle et al. 2000). As part of this study, sampling results from 1998 and 1999 (Arbuckle et al. 2000) were compared to results from stream sites surveyed in 1984 and 1985 by Frest (1987). On a statewide basis, this comparison showed sharp declines in the numbers of mussel species ("species richness") in Iowa streams and rivers from the mid-1980s to the late 1990s. For stream segments having four or more species reported for the 1984-95 survey, results of this comparison were used by staff of the Iowa DNR Water Quality Bureau to assess the degree to which the aquatic life uses of the sampled stream segments are supported. The results of this sampling on the Des Moines River, however, do not meet IDNR guidelines for developing an assessment of support for the aquatic life uses. Species richness of freshwater mussels at the one sample site in this segment was 2 in the 1984-85 period and was 0 in the 1998-99 period, respectively, for percent change of minus 100%. Based on these results, the aquatic life uses are considered “not assessed” due (1) to IDNR’s assessment methodology in which assessment decisions are developed only for those stream segments having an average of four or more species reported in the 1984-85 (Frest) survey and (2) the difficulty of interpreting status of mussel communities showing relatively low species richness during the both the historical (1984-85) and current (1998-99) surveys.
Fish consumption uses are assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Dolliver State Park in 2005. The composite samples of fillets from common carp and freshwater drum had low levels of contaminants. Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.183 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of freshwater drum fillets were as follows: mercury: 0.139 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 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 2005 RAFT sampling conducted in this assessment segment: levels of all contaminants from this monitoring were below advisory trigger levels, thus suggesting the continued “full support” of fish consumption uses.
