Missouri River IA 06-WEM-1715

from confluence with Boyer R. (Pottawattamie Co.) to confluence with Little Sioux R. at river mile 669.2 in Harrison Co.

Open Data Collection Period Modal

For purposes of developing stream/river water quality assessments for integrated reporting, three years of water quality data are typically used for both conventional pollutant parameters (e.g., indicator bacteria) and the less frequently monitored toxic parameters (e.g., toxic metals). Since the 2004 IR cycle, DNR has used a three-year data gathering period for streams, rivers, and beaches. For most assessments, the use of three years of data increases the number of samples upon which the decision on use support is based and helps address the problem of weather-related year-to-year fluctuations in water quality.

Due to the lower sampling frequency in Iowa’s ambient lake, biological, fish kill, and fish tissue monitoring programs, five years of data are used for developing IR assessments and for identifying Section 303(d) listings.

Data Type	Data Timeframe
Beach Sampling Data	CY 2014 - 2016
Stream/River Water Quality Data	CY 2014 - 2016
Lake Water Quality Data	CY 2012 - 2016
Biological Sampling Data	CY 2012 - 2016*
Fish Kill Data	CY 2012 - 2016
Fish Tissue Sampling Data	CY 2012 - 2016
Continuous Dissolved Oxygen Sampling Data	CY 2012 - 2016
*Biological sites sampled in both 2011 and 2015 were also assessed.

Open Segment Map
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Cycle: 2018
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 5/31/2019 10:56:23 AM
Updated: 7/30/2019 9:36:24 AM

Use Support

Class A1

Recreation - Primary contact

Partially Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Partially Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2016

Impairment Rationale

Listing by adjacent state

Data Source

Ambient monitoring: adjacent state

TMDL Priority

Tier III

Class BWW1

Aquatic Life - Warm Water Type 1

Partially Supported

Flow Alteration: Hydrologic Modification

Support Level

Partially Supported

Impairment Code

4c - Non-pollutant caused impairment. No TMDL needed.

Cause Magnitude

Moderate

Status

Continuing

Source

Hydromodification: Dam Release

Source Confidence

Moderate

Cycle Added

1992

Impairment Rationale

Adverse impacts on plant/animal communities

Data Source

Special project/study

Habitat Alterations: Channel Modifications

Support Level

Partially Supported

Impairment Code

4c - Non-pollutant caused impairment. No TMDL needed.

Cause Magnitude

Moderate

Status

Continuing

Source

Hydromodification: Habitat Modification

Source Confidence

Moderate

Cycle Added

1992

Impairment Rationale

Adverse impacts on plant/animal communities

Data Source

Special project/study

Class HH

Human Health -

Fully Supported

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 (primary contact recreation) uses remain assessed as "partially supported" based on the bacterial impairment of recreation uses identified by the Nebraska Department of Environmental Quality. The Class B(WW1) aquatic life uses remain assessed as "partially supported" based on information from local fisheries biologists on impacts related to historic flow modification and habitat alterations in this segment of the Missouri River. The fish consumption uses remain assessed as "fully supported" based on results of fish contaminant monitoring in 2009. The sources of information for this assessment include (1) results of U.S. EPA/DNR fish tissue monitoring near Little Sioux in 2009 and (2) information from Nebraska fisheries biologists.

Assessment Explanation

The Class A1 (primary contact recreation) uses are assessed as "partially supporting" based on the bacterial impairment identified for this assessment segment by the state of Nebraska. A TMDL for the Nebraska impairment in this segment of the Missouri River was approved by EPA in 2007. Because Iowa DNR did not participate in the preparation of this TMDL, this impairment is appropriate for Category 5a of Iowa's Integrated Report.

The Class B(WW1) uses remain assessed (evaluated) as "partially supported" (IR 4c, non-pollutant stressor) based on the assessment developed for the 1998, 2000, and 2002 reports (i.e., habitat alterations and flow modifications that resulted from development of the river for navigation uses in the mid-Twentieth Century). This assessment was developed in consultation with the Missouri River fisheries biologist for the state of Nebraska.

Fish consumption uses are assessed (monitored) as "fully supported" based on results of U.S. EPA/DNR fish tissue (RAFT) monitoring in 2009 near Little Sioux in Harrison County. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.062 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm. The level of mercury in the composite sample of flathead catfish fillets was 0.156 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 2009 RAFT sampling conducted at this river segment show that the levels of contaminants do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.

Monitoring and Methods

Assessment Key Dates

8/11/2009

Fish Tissue Monitoring

Methods

120

Surveys of fish and game biologists/other professionals

150

Monitoring data more than 5 years old

260

Fish tissue analysis

420

Indicator bacteria monitoring