Des Moines River IA 04-UDM-1212

Assessment Comments

Assessment is based on: (1) water quality and fish contaminant monitoring conducted during the 2008-2010 assessment period approximately two miles downstream from Saylorville Dam at Sycamore Access (NW 66th Street) by Iowa State University as part of the Des Moines River Water Quality Study and (2) results of IDNR/UHL ambient city monitoring upstream from Des Moines also at the Sycamore Access (NW 66th Street; STORET station 10770002) during the 2008-2010 assessment period.

Basis for Assessment

[Note:  Prior to the 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, this segment is also now presumptively 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 presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "fully supported" based on monitoring of indicator bacteria from 2008-2010.   The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported” based on results of ambient chemical/physical monitoring from 2008-2010.   Fish consumption uses are assessed (monitored) as "fully supported" based on results of annual fish contaminant monitoring during the 2008-2010 period.   The assessments of support of the beneficial uses are based on results of (1) water quality and fish contaminant monitoring conducted during the 2008-2010 assessment period approximately two miles downstream from Saylorville Dam at Sycamore Access (NW 66th Street) by Iowa State University (under contract with the U.S.   Army Corps of Engineers) as part of the Des Moines River Water Quality Study (see Lutz and Steffen 2009, Lutz 2010, and Lutz 2011) and (2) results of IDNR/UHL ambient city monitoring upstream from Des Moines also at the Sycamore Access (NW 66th Street; STORET station 10770002) during the 2008-2010 assessment period.  

EXPLANATION:  The presumptive Class A1 uses are assessed (monitored) as "fully supported" based on results of ambient water quality monitoring conducted by both ISU/ACOE and IDNR/UHL approximately two miles downstream from Saylorville Dam at Sycamore Access.   Results from ambient bacterial monitoring conducted by ISU/ACOE and by IDNR/UHL at Sycamore Access located approximately two miles downstream from Saylorville Dam continue to suggest that Class A1 uses of the Des Moines River upriver from Interstate 80/35 are fully supported.   The geometric means of indicator bacteria (E.  coli) in the 22 samples collected during the recreational seasons of 2008 through 2010 at IDNR station 10770002 upstream from Des Moines at Sycamore Access were as follows:  the 2008 geometric mean was 16 orgs/100 ml, the 2009 geometric mean was 19 orgs/100 ml, and the 2010 geometric mean was 32 orgs/100 ml.   All three geometric means meet the Class A1 criterion of 126 orgs/100 ml.   Only one of the 22 samples (5%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml.  

Similarly, the geometric means of indicator bacteria (E.  coli) in the 27 samples collected during the recreational seasons of 2008 through 2010 at ISU/ACOE station 5 at Sycamore Access were as follows:  the 2008 geometric mean was 19 orgs/100 ml, the 2009 geometric mean was 8 orgs/100 ml, and the 2010 geometric mean was 17 orgs/100 ml.   All three geometric means are well below the Class A1 criterion of 126 orgs/100 ml.   Three of the 27 samples (11%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml.   According to the IDNR assessment/listing methodology, however, the percentage of samples exceeding Iowa’s single-sample maximum criterion is not significantly greater than 10%; thus, this percentage does not suggest impairment of the Class A1 uses.  

According to U.S.  EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, because all recreation season geometric means from the IDNR and ISU/ACOE ambient monitoring stations are below the respective water quality criterion, the primary contact recreation uses should be assessed as "fully supported".  

The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported.”  Results from ISU/ACOE monitoring at the Sycamore Access station show no violations of Class B(WW1) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen in the approximately 66 samples collected at this station during the 2008-2010 assessment period.   One of the 12 samples analyzed during this period for toxic metals contained a level of copper above the acute Class B(WW1) criterion.   According to IDNR’s assessment/listing methodology, and according to U.S.  EPA assessment guidance, more than one violation of a toxic contaminant in a three-year period suggests impairment of the aquatic life use.   Thus, the single violation of the Class B(WW1) criterion for copper during the 2008-10 assessment period does not indicated impairment the aquatic life uses.   No violations of Class B(WW1) criteria occurred in the 12 samples analyzed for other toxic metals (e.g., cadmium, mercury, nickel, and zinc).   Similarly, results from the IDNR/UHL city monitoring station at Sycamore Access also suggest that the Class B(WW1) aquatic life uses are "fully supported.”  None of the 33 samples collected during the 2008-2010 assessment period exceeded Class B(WW1) criteria for dissolved oxygen, pH, or ammonia-nitrogen.   Neither of the two samples analyzed for toxic metals and neither of the two samples analyzed for pesticides exceeded the respective Class B(WW1) criteria.  

Fish consumption (HH) uses are assessed (monitored) as “fully supported”.   Fish contaminant monitoring conducted downstream from Saylorville Reservoir by ISU/ACOE in 2008, 2009, and 2010 showed low levels of contaminants (dieldrin, heptachlor epoxide, chlordane, alachlor, trifuluralin, and chlorpyrifos) in composite samples of whole fish common carp.   In addition to these pesticide parameters, composite samples of whole-fish common carp were analyzed for PCBs and fillets from largemouth bass were analyzed for mercury during 2009 and 2010.   Levels of PCBs in samples of whole-fish common carp were below levels of detection in both years.   The results showed low levels of mercury in the samples.   The mercury level in both years’s samples was 0.12 mg/kg; this level is well below Iowa’s consumption advisory threshold for a 1 meal/week advisory of 0.3 mg/kg.   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.   The fish contaminant data generated from the 2008, 2009, and 2010 ISU/ACOE samplings (or from previous ISU/ACOE monitoring) conducted in the segment of the Des Moines River immediately downstream from Saylorville Reservoir show that levels of contaminants do not exceed any of the IDPH/IDNR consumption 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 and Steffen 2009, Lutz 2010, and Lutz 2011; the URL for the Des Moines River Water Quality Monitoring Network web site is http://home.eng.iastate.edu/~dslutz/dmrwqn/dmrwqn.html.