Raccoon River IA 04-RAC-1116
mouth (at Des Moines Polk Co.) to the Polk/Dallas county line
- Assessment Cycle
- 2018
- Release Status
- Final
- Data Collection Period
- Overall IR Category
- 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
- Trend
- Unknown
- Created
- 7/10/2019 8:57:03 AM
- Updated
- 7/10/2019 2:31:05 PM
The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" (IR 4a) based on results of monitoring for indicator bacteria (E. coli). The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" (IR 2a) based on results of ambient chemical/physical water quality monitoring. The Class C (drinking water) uses are assessed (monitored) as "not supported" (IR 4a) due to levels of nitrate that exceed state water quality standards and U.S. EPA’s maximum contaminant level (MCL). Human Health/Fish Consumption uses remain assessed (evaluated) as "fully supported" (IR 2a) based on results of fish contaminant monitoring in 2010 and toxics monitoring from 2012-2014. The assessments of support of the beneficial uses of this river segment are based on (1) results of monitoring conducted from 2012-2014 by Iowa State University (under contract with the U.S. Army Corps of Engineers) (ISU/ACOE) conducted at Van Meter (STORET Station 17250001) as part of the Des Moines River Water Quality Study, (2) monitoring conducted on the Raccoon River by the Des Moines Water Works during the 2012-2014 assessment period, (3) results of IDNR/UHL ambient city monitoring upstream from Des Moines at Van Meter (station 10250002) from January 2012 through September 2014, and (4) results of U.S. EPA / IDNR fish tissue (RAFT) monitoring near Booneville in 2010.
Note: This assessment is also used for the adjacent upstream segment of the Raccoon River (IA 04-RAC-0010-2). Results from the Des Moines Water Works, ISU/ACOE monitoring station located at Van Meter, and the DNR/UHL station located upstream from Des Moines all suggest that Class A1 uses should be assessed as "partially supported" due to high levels of indicator bacteria.The geometric means of indicator bacteria (E. coli) in the 501 samples collected during the recreational seasons of 2014 through 2016 by the Des Moines Water Works were as follows: the 2014 geometric mean was 352 orgs/100 ml, the 2015 geometric mean was 420 orgs/100 ml, and the 2016 geometric mean was 293 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. 296 of the combined 501 samples (59%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml.The geometric means of indicator bacteria (E. coli) in the 6 samples collected during the 2014 recreational season at DNR station 10250002 (Raccoon River Upstream of Des Moines (US2)) were as follows: the 2014 geometric mean was 930 orgs/100 ml. The recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Five of the combined 6 samples (83%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml.The geometric means of indicator bacteria (E. coli) in the 50 samples collected during the recreational seasons of 2014 through 2016 ISU/ACOE monitoring station (10250001) located at Van Meter were as follows: the 2014 geometric mean was 430 orgs/100 ml, the 2015 geometric mean was 907 orgs/100 ml, and the 2016 geometric mean was 261 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Thirty Nine of the combined 50 samples (78%) 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 a recreation season geometric mean exceeds the respective water quality criterion, the contact recreation uses should be assessed as ”impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “partially supported”. Despite the ongoing impairment of the Class A1 uses, levels of indicator bacteria during the recreation seasons of 2014 through 2016 were relatively low. The Class B(WW1) aquatic life uses of this river segment are assessed as “fully supporting” based on results of chemical/physical water quality data. Results of chemical/physical water quality monitoring at DNR station 10250002 (Raccoon River Upstream of Des Moines (US2)) suggest “full support” of the aquatic life uses. Monitoring showedno violations of Class B(WW1) water quality criteria for 9 Ammonia samples (maximum = 0.3 mg/L), 9 Dissolved Oxygen samples (minimum = 7.7 mg/L), 9 pH samples (range = 7.5 to 8.5), 9 Temperature samples (maximum = 23.3° c), 9 Chloride samples (maximum = 36 mg/L), or 9 Sulfate samples (maximum = 67 mg/L) occurred during monitoring in 2014.Results of chemical/physical water quality monitoring ISU/ACOE monitoring station (10250001) located at Van Meter also suggest “full support” of the aquatic life uses. Monitoring showedno violations of Class B(WW1) water quality criteria for 66 Ammonia samples (maximum = 0.9 mg/L), 66 Dissolved Oxygen samples (minimum = 6.1 mg/L), 66 pH samples (range = 7.4 to 8.9), 66 Temperature samples (maximum = 28.9° c), 12 Chloride samples (maximum = 38.4 mg/L), or 12 Sulfate samples (maximum = 56.8 mg/L) occurred during monitoring from January 2014 to December 2016.Results of chemical/physical water quality monitoring by the Des Moines Water Works also suggest “full support” of the aquatic life uses. Monitoring showedno violations of Class B(WW1) water quality criteria for 738 Temperature samples (maximum = 28.9° c), 819 Chloride samples (maximum = 261.6 mg/L), or 825 Sulfate samples (maximum = 82.6 mg/L) occurred during monitoring from January 2014 to December 2016.3 of the 755 samples (0%) analyzed for pH (range = 7.5 to 9) 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) and Iowa DNR's assessment/listing methodology, a violation frequency of significantly 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.
Note: A TMDL for nitrate and pathogen indicators (E. coli) was prepared by DNR and approved by EPA in June 2008. Because this TMDL covered the primary Section 303(d) impairments identified for the 2006 assessment/listing cycle, this waterbody was moved from IR Category 5a from the 2006 assessment/listing cycle to IR Category 4a (impaired; TMDL approved) for the 2008 cycle. This river segment remains in IR Category 4a for the current cycle.