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
- 2018
- Release Status
- Final
- Overall IR
- 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
- Trend
- Unknown
- Created
- 8/1/2019 2:49:02 PM
- Updated
- 8/1/2019 3:00:38 PM
The Class A1 (primary contact recreation) uses are assessed as "partially supporting" due to levels of indicator bacteria (E. coli) that slightly exceed state water quality standards. The Class B(WW1) aquatic life uses are assessed as "fully supported" based on the results of the chemical/physical water quality monitoring conducted from 2014 through 2016. Fish consumption uses remain assessed (monitored) as "fully supported" based on results of DNR/SHL fish contaminant monitoring in 2006. The assessments of support of the beneficial uses are based on results of (1) water quality monitoring conducted from 2014-2016 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, (2) DNR/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 DNR/SHL REMAP biological monitoring project (REMAP Site 221). The water quality sites used for this assessment are actually located in the adjacent downstream segment: https://programs.iowadnr.gov/adbnet/Segments/1020
Note: 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 remains in IR Category 4a (TMDL approved). 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 41 samples collected during the recreational seasons of 2014 through 2016 at ISU/ACOE Station 7 (17770003) at County Road S35 near Runnells were as follows: the 2014 geometric mean was 284 orgs/100 ml, the 2015 geometric mean was 357 orgs/100 ml, and the 2016 geometric mean was 162 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Nineteen of the combined 41 samples (46%) 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). Samples collected during the 2014 recreational seasons at DNR station 10770003 downstream from Des Moines was 523 orgs/100 and four of the combined 6 samples (67%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml.Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as "partially supported." Results from both the ISU/ACOE and DNR/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 9 samples collected at the DNR station during the 2014 assessment period. At the ISU/ACOE station, no violations of Class B(WW1) water quality criteria for dissolved oxygen, ammonia, temperature, or pH occurred in the 58 samples collected during the 2014-2016 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 DNR/SHL 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 DPH/DNR 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.