Des Moines River IA 04-LDM-1021
from confluence with South R. (S12 T77N R22W Warren Co.) to confluence with North R. in S36 T78N R23W Polk Co.
- Cycle
- 2016
- Release Status
- Final
- Overall IR
- 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
- Trend
- Unknown
- Created
- 10/17/2016 2:45:35 PM
- Updated
- 10/17/2016 2:47:10 PM
The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supporting" (IR 4a) due to levels of indicator bacteria (E. coli) that slightly exceed state water quality standards. The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" (IR 2a) based on the results of the chemical/physical water quality monitoring conducted from 2012 through 2014. Fish consumption uses remain assessed (monitored) as "fully supported" based on results of IDNR/UHL fish contaminant monitoring in 2006 and based on results of monitoring for toxic metals from 2012-2014. The assessments of support of the beneficial uses are based on results of (1) water quality monitoring conducted from 2012-2014 by Iowa State University (under contract with the U.S. Army Corps of Engineers) (ISU/ACOE) upstream from Red Rock Reservoir (ISU/ACOE Station 7 at County Road S35 near Runnells (STORET Station 17770003) as part of the Des Moines River Water Quality Study (see Lutz 2013 and Lutz 2014), (2) IDNR/SHL ambient city monitoring downstream from Des Moines near Runnells from 2012 through 2014 (STORET station 10770003) and (3) results of 2006 fish contaminant monitoring conducted as part of the IDNR/UHL REMAP biological monitoring project (REMAP Site 221).
Note: 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 (TMDL approved). The Class A1 primary contact recreation uses are assessed (monitored) as "not supported" based on results of monitoring for indicator bacteria (E. coli) at both the IDNR ambient station and the ISU/ACOE station near Runnells. The geometric means of indicator bacteria (E. coli) in the 23 samples collected during the recreational seasons of 2012 through 2014 at IDNR station 10770003 downstream from Des Moines were as follows: the 2012 geometric mean was 139 orgs/100 ml, the 2013 geometric mean was 123 orgs/100 ml, and the 2014 geometric mean was 587 orgs/100 ml. The 2012 and 2014 geometric means slightly exceeded the Class A1 criterion of 126 orgs/100 ml; the 2013 geometric mean was below (met) the Class A1 criterion. Nine of the 24 samples (39%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml. 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 7 were as follows: the 2012 geometric mean was 71 orgs/100 ml, the 2013 geometric mean was 142 orgs/100 ml, and the 2014 geometric mean was 284 orgs/100 ml. The 2013 and 2014 geometric means slightly exceed the Class A1 criterion of 126 orgs/100 ml. Twelve of the 36 samples (33%) 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 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 “impaired.” Regardless of the impairment, levels of indicator bacteria in this river segment were relatively low during the 2012-2014 assessment period and in previous assessment periods. Results from the both the ISU/ACOE and IDNR/SHL monitoring stations at Runnells suggest that the Class B(WW1) aquatic life uses should be assessed (monitored) as "fully supported.” No violations of Class B(WW1) water quality criteria for dissolved oxygen, pH, temperature, or ammonia-nitrogen, chloride or sulfate occurred in the 33 samples collected at the IDNR/SHL station during the 2012-2014 assessment period. At the ISU/ACOE station, no violations of Class B(WW1) water quality criteria for dissolved oxygen, ammonia, temperature, pH, chloride, or sulfate occurred in the 66 samples collected during the 2012-2014 assessment period. Fish consumption uses remain assessed (evaluated) as “fully supported” based on results fish contaminant monitoring conducted in this assessment segment in September 2006 as part of the IDNR/UHL REMAP project (Site 221). This monitoring showed low levels of the primary contaminants in the composite samples of common carp fillets: mercury: 0.239 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. 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. The fish contaminant data generated from the 2006 REMAP sampling conducted in this assessment segment shows that the levels of contaminants do not exceed any of the IDPH/IDNR consumption advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody. In addition, results of monitoring for toxic metals showed no violations of the respective Class HH (Human Health) criteria for cadmium, copper, or mercury in the nine samples analyzed at ISU/ACOE Station 7.