Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Raccoon River IA 04-RAC-1116

mouth (at Des Moines Polk Co.) to the Polk/Dallas county line

Assessment Cycle
2020
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
9/18/2020 2:19:53 PM
Updated
10/13/2020 6:59:47 AM
Assessment conducted in accordance with Iowa's 2020 IR methodology
Use Support
Class A1
Recreation
Primary contact
Partially Supported
Impairments
Support Level
Partially Supported
Impairment Code
4a - Pollutant-caused impairment. TMDL has been completed.
Cause Magnitude
Moderate
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
Cycle Added
2002
Impairment Rationale
Geometric mean criterion exceeded
Data Source
Ambient monitoring: Corps of Engineers/ISU/UI
Class BWW1
Aquatic Life
Warm Water Type 1
Fully Supported
Class C
Drinking Water
Not Supported
Impairments
Support Level
Not Supported
Impairment Code
4a - Pollutant-caused impairment. TMDL has been completed.
Cause Magnitude
High
Status
Continuing
Source
Agriculture
Source Confidence
Moderate
Cycle Added
1998
Impairment Rationale
Significantly > 10% of samples fail to meet criterion
Data Source
Ambient monitoring: municipal water supply
Class HH
Human Health
Not Assessed
General Use
General Use water
Not Assessed
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The Class A1 use was assessed as "partially supported" based on results of monitoring for indicator bacteria (E. coli). The Class BWW1 use was assessed as "fully supported" based on results of ambient chemical/physical water quality monitoring. The Class C use was assessed as "not supported" due to levels of nitrate that exceeded state water quality standards and U.S. EPA’s maximum contaminant level (MCL). All other designated uses are “not assessed.”  Note: A TMDL for nitrate and pathogen indicators (E. coli) was prepared by DNR and approved by EPA in June 2008. Because this TMDL covers the primary Section 303(d) impairments identified for this IR cycle, this waterbody was moved from IR Category 5a to IR Category 4a (impaired; TMDL approved).

Assessment Explanation

Sources of Data:

Data Source

Data Source ID

Data Type

Data Age

Site ID

Site Name

Site Description

DMWW

13

WQ

CY 2016-2018

99990003

Raccoon River

Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples / # Years

2016 Geometric Mean

2017 Geometric Mean

2018 Geometric Mean

Annual Geometric Mean Violation

# Violations

% Violations

Significantly >10% Violations

Assessment Type

Support Level

99990003

13

510 / 3

293.17

200.68

247.95

Yes

249

49%

Yes

Monitored

Partial


Class A1 - pH:

Site ID

Data Source ID

# Samples / # Years

Maximum Value

Mean Value

Median Value

# Violations

% Violations

Significantly >10% Violations

Assessment Type

Support Level

99990003

13

759 / 3

8.92

8.29

8.31

0

0%

No

Monitored

Full


Class BWW1 - Conventional Parameters:

Site ID

Data Source ID

Parameter Name

# Samples / # Years

Maximum Value

Mean Value

Median Value

# Acute / Chronic Violations

% Acute/ Chronic Violations

Significantly >10% Violations

Assessment Type

Support Level

99990003

13

Chloride

758 / 3

168.79

22.03

20.99

0 / 0

0% / 0%

No

Monitored

Full

99990003

13

pH

759 / 3

8.92

8.29

8.31

0 / NA

0% / NA

No

Monitored

Full

99990003

13

Sulfate

758 / 3

68.2

29.95

29.6

0 / NA

0% / NA

No

Monitored

Full

99990003

13

Temperature

752 / 3

29.4

12.7

12.8

0 / 0

0% / 0%

No

Monitored

Full


Class C - Conventional Parameters:

Site ID

Data Source ID

Parameter Name

# Samples / # Years

Maximum Value

Mean Value

Median Value

# Violations

% Violations

Significantly >10% Violations

Assessment Type

Support Level

99990003

13

Chloride

759 / 3

168.79

22.02

20.99

0

0%

No

Monitored

Full

99990003

13

Inorganic nitrogen (nitrate and nitrite)

759 / 3

14.07

7.078

7.07

173

23%

Yes

Monitored

Partial


Class HH - Fish Tissue Sampling: No Data

Previous fish tissue monitoring that occurred in the adjacent segment has been removed from this assessment.





Monitoring and Methods
Assessment Key Dates
1/4/2016
Fixed Monitoring Start Date
12/31/2018
Fixed Monitoring End Date
Methods
210
Fixed station physical/chemical monitoring (conventional pollutants only)
270
PWS chemical monitoring (ambient water)
420
Indicator bacteria monitoring