Des Moines River IA 04-UDM-1211

The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on results of ambient monitoring for indicator bacteria (E.coli) by the Des Moines Water Works at the Second Avenue Bridge in Des Moines. Despite this impairment, results from ambient bacterial monitoring conducted by ISU/ACOE and by DNR/SHL at the next upstream monitoring station (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 (i.e., segment IA 04-UDM-1212) are fully supported. The 2014 geometric means 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 nine samples (0%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml.

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.

In contrast to the results from ISU/ACOE and DNR/SHL monitoring near Saylorville Dam at the Sycamore Access station, however, the results of bacterial monitoring by the Des Moines Water Works downriver from the I80/I35 bridge near the Second Avenue Bridge during recreational seasons of 2014 through 2016 suggest (1) slightly higher levels of indicator bacteria and (2) that the Class A1 uses should be assessed as "partially supported.” Levels of indicator bacteria (E.coli) in the Des Moines River were monitored by DMWW on most weekdays during 2014 through 2016 with a total of 494 samples being analyzed. The Class A1 (primary contact recreation) uses are assessed (monitored) as ""partially supported"" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 494 samples collected during the recreational seasons of 2014 through 2016 at the DMWW monitoring station (Second Avenue Bridge in Des Moines) were as follows: the 2014 geometric mean was 74 orgs/100 ml, the 2015 geometric mean was 120 orgs/100 ml, and the 2016 geometric mean was 66 orgs/100 ml. None of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Of the combined 494 samples, 125 samples (25%) 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). Also, if significantly more than 10% of the samples exceed Iowa’s single-sample maximum value of 235 E. coli orgs/100 ml, the Class A1 uses should be assessed as "partially supported." This assessment approach is based on U.S. EPA guidelines (see pgs 3-33 to 3-35 of U.S. EPA 1997b).

All geometric means for the recreation seasons of 2014-2016 at the DMWW monitoring station (Second Avenue Bridge in Des Moines) are below the geometric mean criterion. The percentage of violations of Iowa’s single-sample maximum criterion for E. coli (235 orgs/100 ml), however, is significantly greater than 10%. Thus, the primary contact recreation uses are assessed as "partially supported." Despite this impairment, levels of indicator bacteria in this segment of the Des Moines River are very low relative to levels in other Iowa rivers. Levels of indicator bacteria tend to be very low in river segments immediately downstream from all of Iowa’s federal flood control reservoirs (e.g., Saylorville, Coralville and Red Rock reservoirs).

Note 1: A TMDL for bacteria was prepared by DNR and approved by U.S. EPA in March 2010. Because this TMDL covers all the identified impairments for the assessment segment, this segment was moved to IR Category 4a (impaired; TMDL approved) for the 2010 Integrated Reporting Cycle and remains in IR Category 4a.

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.

Additionally results of chemical/physical water quality monitoring by the Des Moines Water Works near the Second Avenue Bridge also suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW1) water quality criteria for 743 Temperature samples (maximum = 27.8° c), 828 Chloride samples (maximum = 243.3 mg/L), or 827 Sulfate samples (maximum = 146.9 mg/L) occurred during monitoring from January 2014 to December 2016.Two of the 759 samples (0%) analyzed for pH (range = 7.3 to 9.4) violated the Class B(WW1) criteria during the 2014-2016 monitoring period.According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17), a violation frequency of greater than 10% for conventional parameters such as pH suggests impairment of aquatic life uses. Because the frequency of violations for this parameter is not greater than 10 percent, these results do not suggest impairment of the Class B(WW1) aquatic life uses.

Results of Class C (drinking water) monitoring at the DMWW monitoring station (Second Avenue Bridge in Des Moines) suggest “partial support” of the Class C (drinking water) uses. Monitoring showed no violations of Class C (drinking water) criteria for 830 Chloride samples (maximum = 243.3 mg/L and average = 31.5 mg/L) or 829 Fluoride samples (maximum = 780 ug/L and average = 349.36 ug/L) occurred during monitoring from January 2014 to December 2016. However, 360 of the 831 samples (43%) analyzed for nitrate-nitrite (maximum = 17.42 mg/L and average = 8.81 mg/L) violated the Class C (drinking water) criteria during the 2014-2016 monitoring period.

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 2: 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.