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 DNR/SHL. The 2014 geometric mean of indicator bacteria (E. coli) in the six samples collected during the recreational season in 2014 at DNR station 10770002 upstream from Des Moines at Sycamore Access was 32 orgs/100 ml. The recreation season geometric mean did not exceed the Class A1 geometric mean criterion of 126 orgs/100 ml. None of the six samples (0%) 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 51 samples collected during the recreational seasons of 2014 through 2016 at ISU/ACOE station 5 (17770001) at Sycamore Access were as follows: the 2014 geometric mean was 20 orgs/100 ml, the 2015 geometric mean was 45 orgs/100 ml, and the 2016 geometric mean was 22 orgs/100 ml. None of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Six of the combined 51 samples (12%) 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 DNR’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 on the water quality sampling in this segment, the Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported.” Results of chemical/physical water quality monitoring at DNR 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 9 Ammonia samples (maximum = 0.5 mg/L), 9 Dissolved Oxygen samples (minimum = 8.1 mg/L), 9 pH samples (range = 7.7 to 8.1), 9 Temperature samples (maximum = 25.8° c), 9 Chloride samples (maximum = 73 mg/L), or 9 Sulfate samples (maximum = 130 mg/L) occurred during monitoring from January 2014 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 = 6.3 mg/L), 66 pH samples (range = 7.4 to 8.4), 66 Temperature samples (maximum = 27.6° c), 12 Chloride samples (maximum = 69.1 mg/L), or 12 Sulfate samples (maximum = 135.3 mg/L) occurred during monitoring from January 2014 to December 2016. None of the four samples analyzed during this period for copper 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 DNR 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 DNR/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 DNR’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). DNR 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 Class C (drinking water) monitoring at ISU/ACOE station 5 (17770001) also suggested “partial support” of the Class C (drinking water) uses. Monitoring showed no violations of Class C (drinking water) criteria for 12 Chloride samples (maximum = 69.1 mg/L and average = 30.5 mg/L) occurred during monitoring from January 2014 to December 2016. However, 25 of the 66 samples (38%) analyzed for nitrate-nitrite (maximum = 17 mg/L and average = 8.49 mg/L) violated the Class C (drinking water) criteria during the 2014-2016 monitoring period.

Results of Class C (drinking water) monitoring at DNR station 10770002 suggest “full support” of the Class C (drinking water) uses. Monitoring showed no violations of Class C (drinking water) criteria for 9 Chloride samples (maximum = 73 mg/L and average = 39.2 mg/L), 9 nitrate-nitrite samples (maximum = 8.9 mg/L and average = 3.46 mg/L), 14 Alachlor samples (maximum = 0.05 ug/L and average = 0.03 ug/L), 7 Atrazine samples (maximum = 1.8 ug/L and average = 0.44 ug/L), 7 Carbofuran samples (maximum = 0.05 ug/L and average = 0.05 ug/L), or 7 Cyanazine samples (maximum = 0.05 ug/L and average = 0.05 ug/L) occurred during monitoring from January 2014 to September 2014.

DNR's assessment methodology states that if significantly more than 10% of samples exceed the nitrate MCL, the Class C drinking water uses should be assessed as “partially supported”.

Note: A TMDL for nitrate was prepared by DNR and approved by EPA in September 2009. Because this TMDL covers the nitrate impairment identified for this waterbody, this impairment remains in IR Category 4a (impaired; TMDL approved) for this cycle.

Fish consumption (HH) uses are assessed (monitored) as “fully supported” based on results of water quality and fish contaminant monitoring at ISU/ACOE station 5 (17770001) at Sycamore Access in 2014-2016. None of the four samples analyzed for copper contained levels that exceeded the Class HH (human health-fish) criteria. Fish contaminant monitoring conducted downstream from Saylorville Reservoir by ISU/ACOE in 2014, 2015 and 2016 showed low levels of pesticide contaminants (dieldrin, chlordane, trifuluralin, and chlorpyrifos) in composite samples of whole fish 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 2016. Levels of PCBs in samples of whole-fish common carp were below levels of detection in 2016. In addition to these pesticide parameters, fillets from smallmouth bass were analyzed for mercury in in 2014 and fillets from largemouth bass were analyzed for mercury in in 2015 and 2016. The results showed that the level of mercury in the 2014 sample from smallmouth bass (0.69 ppm) was above the Hg level of concern (0.3 ppm); however the samples from the 2015 largemouth bass (0.13 ppm) and the 2016 largemouth bass (0.11 ppm) were both below the level of concern. The potential fish consumption impairment is removed for the current cycle.

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