Assessment Comments

Assessment is based on results of monitoring NW of Boone conducted by Iowa State Univ. from 2002-04 as part of the ACOE's Des Moines R./Saylorville Res./Red Rock Res. water quality study.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses remain assessed (monitored) as "fully supported " based on results of ambient chemical/physical water quality monitoring.   Fish consumption uses remain “not assessed” due to the lack of recent fish contaminant monitoring in this river segment.   The assessments of support of the beneficial uses are based on results of water quality monitoring conducted during the 2002-2004 assessment period by Iowa State University (under contract with the U.S.  Army Corps of Engineers) (ISU/ACOE) as part of the Des Moines River Water Quality Study (see Lutz and Cummings 2003, Lutz 2004, and Lutz et al.  2005).   Results of this assessment do not suggest the need to continue to place this river segment on Iowa's list of waters in need of further investigation.   Thus, this waterbody was moved from IR Category 2b to Category 2a for the 2006 assessment/listing cycle.

EXPLANATION:  The only violation of Class B(WW) WQ criteria for conventional parameters at the ISU/ACOE monitoring station NW of Boone was in one of the 66 samples analyzed for dissolved oxygen during the 2002-2004 assessment period.   The sample collected on August 6, 2002 contained 4.6 mg/l of dissolved oxygen; thus violating Iowa’s Class B(WW) criterion of 5.0 mg/l.   Levels of pH and ammonia-nitrogen did not violate the respective Class B(WW) criteria during the assessment period (N approximately = 66).   According to U.S.  EPA guidelines for Section 305(b) water quality assessments (U.S.  EPA 1997b, page 3-17), the percentage of violations for dissolved oxygen at this station (2%) does not suggest a water quality impairment (the EPA guidelines allow up to 10% violations of these conventional parameters before impairment of water quality is indicated).   None of the 12 samples analyzed for toxic metals (cadmium, lead, and mercury) violated their respective Iowa water quality criteria Thus, these results suggest “full support” of the Class B(WW) aquatic life uses in this segment of the Des Moines River.

Fish consumption uses were not assessed due to lack of recent monitoring information.   However, U.S EPA/IDNR (RAFT) fish tissue monitoring in 1999 on the Des Moines River upstream from this reach at Dolliver State Park showed very low levels of all contaminants in composite samples of fillets from common carp and freshwater drum.   The following is excerpted from the assessment developed for waterbody IA 04-UDM-0040-2 (Des Monies River from near Kalo upriver to the Ft.  Dodge impoundment):  “Fish consumption uses were assessed (evaluated) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Dolliver State Park in 1999.   Because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).   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 1999 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.”