Assessment Comments
Assessment is based on: (1) water quality monitoring conducted during the 2010-2012 assessment period approximately two miles downstream from Saylorville Dam at Sycamore Access (NW 66th Street, ISU station 5; STORET station 17770001) by Iowa State University as part of the Des Moines River Water Quality Study, (2) results of IDNR/SHL ambient city monitoring upstream from Des Moines at the Sycamore Access (NW 66th Street; STORET station 10770002) during the 2010-2012 assessment period and (3) IDNR/SHL biological sampling conducted in 2012 upstream of Des Moines.
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). Also, the Class C designation is applied to this segment to allow retrieval of data for assessing the support of the Class C uses of the downstream segment: IA 04-UDM-0010_2.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "fully supported" (IR 2a) based on monitoring of indicator bacteria from 2010-2012. The Class B(WW1) aquatic life uses are assessed (evaluated) as "partially supported” (IR 2b-u) based on results of IDNR/SHL biological sampling conducted in 2012 upstream of Des Moines. Fish consumption uses are assessed (monitored) as "fully supported" (IR 2a) based on results of annual fish contaminant monitoring during the 2010-2012 period. The assessments of support of the beneficial uses are based on results of (1) water quality and fish contaminant monitoring conducted during the 2010-2012 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 2011, 2012, and 2013), (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 and (3) IDNR/SHL biological sampling conducted in 2012 upstream of Des Moines.
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 24 samples collected during the recreational seasons of 2010 through 2012 at IDNR station 10770002 upstream from Des Moines at Sycamore Access were as follows: the 2010 geometric mean was 32 orgs/100 ml, the 2011 geometric mean was 11 orgs/100 ml, and the 2012 geometric mean was 24 orgs/100 ml. All three geometric means meet the Class A1 criterion of 126 orgs/100 ml. Only two of the 24 samples (8%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml.
Similarly, the geometric means of indicator bacteria (E. coli) in the 29 samples collected during the recreational seasons of 2010 through 2012 at ISU/ACOE station 5 at Sycamore Access were as follows: the 2010 geometric mean was 17 orgs/100 ml, the 2011 geometric mean was 4 orgs/100 ml, and the 2012 geometric mean was 14 orgs/100 ml. All three geometric means are well below the Class A1 criterion of 126 orgs/100 ml. Two of the 29 samples (7%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml.
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, and because less than 10% of the samples collected exceeded Iowa’s single-sample maximum criterion, the primary contact recreation uses should be assessed as "fully supported".
Based just on the water quality sampling in this segment, the Class B(WW1) aquatic life uses should be 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 2010-2012 assessment period. None of the nine samples analyzed during this period for toxic metals (e.g., cadmium, copper, mercury, and lead) exceeded the respective Class B(WW1) criteria. 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 36 samples collected during the 2010-2012 assessment period exceeded Class B(WW1) criteria for dissolved oxygen, pH, or ammonia-nitrogen. Thus, the monitoring results from both the ISU/ACOE and IDNR monitoring stations suggest “full support” of the Class B(WW1) aquatic life uses.
In contrast to the water quality aquatic life assessment, the aquatic life assessment based on biological sampling suggests the aquatic life uses are "partially supporting". This evaluated biological assessment was based on data collected in 2012 as part of the IDNR/SHL large river sampling project. A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa collected in the stream sampling reach. The biological metrics were combined a benthic macroinvertebrate index (BMIBI). The index rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2012 BMIBI score was 32 (fair). The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the BMIBI score with biological impairment criteria (BIC) established from a statistical analysis of biological data collected at stream ecoregion reference sites from 1994-2008. The BMIBI BIC for this ecoregion is 62. This assessment is considered evaluated because the drainage area (5840 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria. Even though this site failed the BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size. According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation).
Fish consumption (HH) uses are assessed (monitored) as “fully supported”. None of the nine samples analyzed for toxic metals (e.g., cadmium, copper, and mercury) contained levels that exceeded their respective Class HH (human health-fish) criteria. Fish contaminant monitoring conducted downstream from Saylorville Reservoir by ISU/ACOE in 2010, 2011, and 2012 showed low levels of pesticide contaminants (dieldrin, heptachlor epoxide, chlordane, alachlor, trifuluralin, and chlorpyrifos) in composite samples of whole fish and fillets of common carp. None of the concentrations for chlordane approached Iowa’s thresholds for issuing a one meal per week consumption advisory. In addition to these pesticide parameters, composite samples of whole-fish common carp were analyzed for PCBs in 2010 and 2012, and fillets from largemouth bass were analyzed for mercury in all three years. Levels of PCBs in samples of whole-fish common carp were below levels of detection in both 2010 and 2012. The results also showed that levels of mercury in the samples were below levels of concern. The mercury levels in fillets from predator fish in 2011 were as follows: largemouth bass: 0.26 ppm; smallmouth bass: 0.23 ppm. In 2012, the level of mercury in the fillets from a largemouth bass was 0.12 ppm. These levels are below Iowa’s consumption advisory threshold for a 1 meal/week advisory of 0.3 ppm. 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 2010, 2011, and 2012 ISU/ACOE samplings 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 2011, 2012, and 2013; the URL for the Des Moines River Water Quality Monitoring Network web site is http://home.eng.iastate.edu/~dslutz/dmrwqn/dmrwqn.html.
