Des Moines River IA 04-UDM-1211

The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" (4a) 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 IDNR/UHL 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-0010_3) are fully supported. 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."

In contrast to the results from ISU/ACOE and IDNR/UHL 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 2010 through 2012 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 2012 through 2014 with a total of 496 samples being analyzed.   The geometric means of indicator bacteria (E.  coli) in the DMWW samples collected during the recreational seasons of 2012 through 2014 near the Second Avenue Bridge were as follows:  the 2012 geometric mean was 23 orgs/100 ml, the 2013 geometric mean was 38 orgs/100 ml, and the 2014 geometric mean was 64 orgs/100 ml.   All three geometric means are below the Class A1 criterion of 126 orgs/100 ml.   Ninety One of the combined 496 samples (18%), however, 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, if all recreation season geometric means meet the respective water quality criterion, the contact recreation uses should be assessed as “fully supporting” (see pgs 3-33 to 3-35 of U.S.  EPA 1997b).   If, however, greater than 10% of the samples exceed the Class A1 single-sample maximum criterion of 235 orgs/100 ml, the primary contact recreation uses should be assessed as “partially supporting”.   Thus, because significantly greater than 10% of the samples from the DMWW monitoring station near Second Avenue exceeded the single-sample maximum criterion, the Class A1 primary contact recreation uses should be assessed as “partially supporting”.   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 IDNR 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 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.

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 250 Temperature samples (maximum = 29.4° c), 779 Chloride samples (maximum = 243.3 mg/L), or 779 Sulfate samples (maximum = 146.9 mg/L) occurred during monitoring from January 2012 to December 2014. Two of the 756 samples (0%) analyzed for pH (range = 7.3 to 9.4) violated the Class B(WW1) criteria during the 2012-2014 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 water quality monitoring in this river segment during the 2010-12 period by the Des Moines Water Works, ISU/ACOE, and IDNR/UHL suggest “partially support” (4a) of the Class C (drinking water) uses. This assessment is in contrast to assessment for previous Integrated Reporting cycle (2014) that had shown no impairment of drinking water uses due to high levels of nitrate but is consistent with the earlier Section 305(b) assessment. Results of monitoring by the Des Moines Water Works in this river segment that showed that only four of the 732 daily samples collected during the 2010-2012 assessment period (less than 1%) contained nitrate above the 10 mg/l MCL. In contrast results of monitoring by the Des Moines Water Works in this river segment that show that one hundred thirty nine of the 759 daily samples collected during the 2012-2014 assessment period (18%) contained nitrate above the 10 mg/l MCL (mean = 4.86 mg/l; median = 1.8 mg/l; maximum = 18.6 mg/l). IDNR'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”.

In contrast results of water quality monitoring in this river segment during the 2010-12 period by ISU/ACOE and IDNR/UHL, however, 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. However, the violation are approaching the greater than 10% minimum of exceedances needed to be classified as impared.  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 do not suggest impairment of the drinking water uses.

Note 2:  A TMDL for nitrate was prepared by IDNR and approved by EPA in September 2009.   Because this TMDL covers the nitrate impairment identified for this waterbody, this impairment was placed again into IR Category 4a (impaired; TMDL approved) for this cycle (2016).

Fish consumption (HH) uses are assessed (monitored) as “partially supported” (3b) 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.