Des Moines River IA 04-UDM-1212

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/SHL.  The geometric means of indicator bacteria (E. coli) in the 23 samples collected during the recreational seasons of 2012 through 2014 at IDNR station 10770002 upstream from Des Moines at Sycamore Access were as follows: the 2012 geometric mean was 24 orgs/100 ml, the 2013 geometric mean was 14 orgs/100 ml, and the 2014 geometric mean was 32 orgs/100 ml.  None of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml.  One of the combined 23 samples (4%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml.

Similarly, the geometric means of indicator bacteria (E. coli) in the 36 samples collected during the recreational seasons of 2012 through 2014 at ISU/ACOE station 5 (17770001) at Sycamore Access were as follows: the 2012 geometric mean was 14 orgs/100 ml, the 2013 geometric mean was 14 orgs/100 ml, and the 2014 geometric mean was 20 orgs/100 ml.  None of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml.  One of the combined 36 samples (3) exceeded Iowa’s 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, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).  Thus, because none of the recreation seasons geometric means exceeded criteria for Class A1 uses, these uses are 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 of chemical/physical water quality monitoring at IDNR station 10770002 upstream from Des Moines at Sycamore Access suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW1) water quality criteria for 33 Ammonia samples (maximum = 0.6 mg/L), 33 Dissolved Oxygen samples (minimum = 6.5 mg/L), 33 pH samples (range = 7.4 to 8.7), 33 Temperature samples (maximum = 28.4° c), 33 Chloride samples (maximum = 73 mg/L), or 33 Sulfate samples (maximum = 130 mg/L) occurred during monitoring from January 2012 to September 2014. Similarly, results of chemical/physical water quality monitoring at ISU/ACOE station 5 (17770001) at Sycamore Access also suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW1) water quality criteria for 66 Ammonia samples (maximum = 1 mg/L), 66 Dissolved Oxygen samples (minimum = 6.7 mg/L), 66 pH samples (range = 7.4 to 8.5), 66 Temperature samples (maximum = 28.2° c), 66 Chloride samples (maximum = 69.1 mg/L), or 66 Sulfate samples (maximum = 135.3 mg/L) occurred during monitoring from January 2012 to December 2014. 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. According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), the EPA guidelines allow up to 10% violations of these conventional parameters before impairment of water quality is indicated. 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 2012-2014 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 2012-2014 BMIBI scores were 29 (poor) and 32, 42 (both 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 (0/3), it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the site used for the assessment 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).

Results of water quality monitoring in this river segment during the 2010-12 period by ISU/ACOE and IDNR/UHL suggest “full support” of the Class C (drinking water) uses.   Results of ambient monitoring for nitrate conducted at ISU/ACOE station 5 (17770001) at Sycamore Access as part of the Iowa State University/Army Corps of Engineers network show “full support” of drinking water uses during the 2012-2014 period:  Ten of the 66 bi-monthly samples (15%) collected during the 2012-2014 assessment period exceeded the nitrate MCL (mean = 5.3 mg/l; median = 3.3 mg/l; maximum = 17.9 mg/l). Based on IDNR's assessment methodology these violations are not significantly greater than 10% of the samples and therefore do not suggest impairment of the Class C (drinking water) uses. In addition, no violations of Class C water quality criteria for 32 Alachlor samples (maximum = 0.1 ug/L), 26 Atrazine samples (maximum = 1.8 ug/L), 26 Carbofuran samples (maximum = 0.1 ug/L), 33 Chloride samples (maximum = 73 mg/L), or 26 Cyanazine samples (maximum = 0.1 ug/L) occurred during monitoring from January 2012 to December 2014.

Similarly, results of ambient monitoring for nitrate conducted at IDNR station 10770002 upstream from Des Moines at Sycamore Access also show “full support” of drinking water uses during the 2012-2014 period:  Three of the 33 samples (9%) collected during the 2012-2014 assessment period exceeded the nitrate MCL (mean = 3.5 mg/l; median = 1.7 mg/l; maximum = 16 mg/l). Based on IDNR's assessment methodology these violations are not significantly greater than 10% of the samples and therefore do not suggest impairment of the Class C (drinking water) uses. In addition, no violations of Class C water quality criteria for 9 Cadmium samples (maximum = 0.4 ug/L), 12 Chloride samples (maximum = 69.1 mg/L), or 9 Lead samples (maximum = 2 ug/L) occurred during monitoring from March 2012 to December 2014. According to IDNR guidelines for Section 305(b) assessments, these results suggest “full support” of the drinking water uses.

Fish consumption (HH) uses are assessed (monitored) as “partially supported” based on results of fish contaminant monitoring at ISU/ACOE station 5 (17770001) at Sycamore Access in 2014. 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 2012, and 2014 showed low levels of pesticide contaminants (dieldrin, chlordane, 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. Composite samples of whole-fish common carp were analyzed for PCBs in 2012. Levels of PCBs in samples of whole-fish common carp were below levels of detection in 2012.  In addition to these pesticide parameters, fillets from largemouth bass were analyzed for mercury in in 2012 and fillets from smallmouth bass were analyzed for mercury in in 2014. The results showed that levels of mercury in the samples from largemouth bass (0.26 ppm) were below levels of concern; however the samples from smallmouth bass (0.69 ppm) were above levels of concern. These levels are aboce Iowa’s consumption advisory threshold for a 1 meal/week advisory of 0.3 ppm.  According to IDNR’s assessment methodology, the single occurrence of contaminant above an advisory trigger level neither warrants issuance of an advisory nor indicates impairment of the fish consumption uses: two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory.  Thus, follow-up monitoring is needed at ISU/ACOE station 5 (17770001) at Sycamore Access.  The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses. Based on this information, fish consumption uses are assessed (monitored) as "partially supported" due to the potential for a fish consumption advisory.

For more information on ISU/ACOE water quality monitoring in this river reach, see Lutz 2013, 2014, and 2015; the URL for the Des Moines River Water Quality Monitoring Network web site is http://home.eng.iastate.edu/~dslutz/dmrwqn/dmrwqn.html.