Assessment Comments
Assessment is based on results of water quality monitoring, fish contaminant monitoring, and fish kill reporting conducted downstream from Red Rock Reservoir during the 2004-2006 assessment period by Iowa State University (under contract with the U.S. Army Corps of Engineers) at ISU/ACOE Station 9 at the Howell Station Landing (STORET station 17630001).
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as "fully supporting" based on results of routine monitoring for indicator bacteria (E. coli). The Class B(WW1) aquatic life uses remain assessed (monitored) as "not supported" due to repeated fish kills immediately downriver from Red Rock Dam. The fish consumption uses are assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2004, 2005, and 2006. The assessments of support of the beneficial uses are based on results of water quality monitoring, fish contaminant monitoring, and fish kill reporting conducted downstream from Red Rock Reservoir during the 2004-2006 assessment period by Iowa State University (under contract with the U.S. Army Corps of Engineers) at ISU/ACOE Station 9 at the Howell Station Landing (STORET station 17630001). This monitoring was conducted as part of the Des Moines River Water Quality Study (see Lutz et al. 2005, Lutz and Francois 2006, and Lutz and Francois 2007).
EXPLANATION: The Class A1 uses are assessed (monitored) as "fully supported" based on results of ambient water quality monitoring from the ISU/ACOE station 0.7 mi downstream from Red Rock Dam. 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.
At this monitoring station, the geometric mean of the 36 samples collected during summers of 2004, 2005 and 2006 was 5 orgs/100 ml; none of the 36 samples exceeded the 235 organism/100 ml single sample maximum criterion. These results, combined with results of previous monitoring, continue to indicate (1) extremely low levels of indicator bacteria in this reach of river and (2) that the lowest levels of indicator bacteria in the state’s streams and river occur immediately downriver from Iowa’s federal flood control reservoirs. According to U.S. EPA guidelines for Section 305(b) reporting, if the geometric mean of E. coli is less than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "fully supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b).
Results from this ISU/ACOE monitoring station also suggest that the Class B(WW1) aquatic life uses are "fully supported"; however, the Class B(WW1) aquatic life uses remained assessed as "not supported" due to reoccurring fish kills in this river segment. No violations of Class B(WW1) water quality criteria for conventional parameters (dissolved oxygen, pH, ammonia-nitrogen) occurred in the 66 samples collected at this station during the 2004-2006 assessment period. Also, none of the 12 samples analyzed for toxic metals violated their respective Class B(WW1) criteria.
Three fish kills were reported for this river segment for the 2004-2007 assessment period by Lutz and Francois (2007). One kill was attributed to thermal (cold) stress; two of the kills were attributed to gas bubble trauma. 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, due to the two fish kills during the 2004-2007 period caused by gas bubble trauma, and due to the history of this type of fish kill in this river reach, the Class B(WW1) aquatic life uses are assessed as "partially supported” and will remain in IR Category 4c (i.e., impairment due to a non-pollutant stressor; TMDL not required).
Fish contaminant monitoring conducted downstream from Red Rock Reservoir by ISU/ACOE in 2004, 2005, and 2006 showed low levels of contaminants (dieldrin, heptachlor epoxide, chlordane, alachlor, trifuluralin, and chlorpyrifos) in composite samples of whole fish and fillets of common carp. In addition to these pesticide parameters, composite samples fillets from common carp and channel catfish from this station were analyzed for mercury in 2004, and composite fillet samples from common carp and largemouth bass were analyzed for mercury in 2005 (this was the first analysis of fish tissue samples for mercury conducted as part of the ISU/ACOE program since 1994). The results showed low levels of mercury in these samples: common carp: 0.04 ppm in 2004 and 0.05 ppm in 2005; channel catfish fillets: 0.06 ppm in 2004; largemouth bass fillets: 0.11 ppm in 2005. This supplemental monitoring for mercury in fish was not conducted during the 2006 sampling season. Based on this information, fish consumption uses are assessed (monitored) as "fully supported".
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 2004, 2005, or 2006 ISU/ACOE sampling (or from previous ISU/ACOE monitoring) conducted in the segment of the Des Moines River immediately downstream from Red Rock Reservoir: the levels of contaminants (chlordane and mercury) do not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.
For more information on ISU/ACOE water quality monitoring in this river reach, see (Lutz et al. 2005, Lutz and Francois 2006, and Lutz and Francois 2007).
