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
2022
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
12/30/2021 6:32:27 AM
Updated
1/28/2022 10:07:46 AM
Assessment conducted in accordance with Iowa's 2022 IR methodology
Use Support
Class A1
Recreation
Primary contact
Not Supported
Impairments
Support Level
Not 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
Fully Supported
Class HH
Human Health
Not Assessed
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The Class A1 use was assessed as "not 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 "fully supported" based on results of ambient chemical/physical water quality monitoring. All other designated uses were “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

Data Sources:

Data Source

Data Source ID

Data Type

Data Age

Site ID

Site Name

Site Description

DMWW

13

WQ

CY 2018-2020

99990003

Raccoon River

Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2018/ 2019/2020)

2018 Geometric Mean

2019 Geometric Mean

2020 Geometric Mean

Violates Annual Geometric Mean?

# 2018 SSM violations / SSM Violations needed for impairment

# 2019 SSM violations / SSM Violations needed for impairment

# 2020 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

99990003

13

170/170/170

248

191

104

YES

92 / 23

73 / 23

47 / 23

YES

Monitored

Not

Class A1 – pH:

Site ID

Data Source ID

# Samples / # Years

Minimum Value

Maximum Value

Mean Value

# Violations

Violations needed for impairment

Violates Significantly >10% Rule?

Assessment Type

Support Level

99990003

13

760 / 3

7.14

8.74

8.27

0

88

NO

Monitored

Full

Class BWW1 - Conventional Parameters:

Site ID

Data Source ID

Parameter Name

# Samples / # Years

Minimum Value

Maximum Value

Mean Value

# Violations

# Acute / Chronic Violations

Violations needed for impairment

Violates Significantly >10% Rule?

Assessment Type

Support Level

99990003

13

Chloride

758 / 3

6.96

168.79

22.81

NA

0 / 0

87

NO

Monitored

Full

99990003

13

pH

760 / 3

7.14

8.74

8.27

0

NA / NA

88

NO

Monitored

Full

99990003

13

Sulfate

758 / 3

5.31

63.81

29.84

0

NA / NA

87

NO

Monitored

Full

99990003

13

Temperature

758 / 3

-1.67

29.44

11.87

0

NA / NA

87

NO

Monitored

Full

Class C - Conventional Parameters:

Site ID

Data Source ID

Parameter Name

# Samples / # Years

Minimum Value

Maximum Value

Mean Value

Median Value

# Violations

Violates Significantly >10% Rule?

Assessment Type

Support Level

99990003

13

Chloride

758 / 3

6.96

168.79

22.81

20.56

0

NO

Monitored

Full

99990003

13

Fluoride

753 / 3

80

490

297

310

0

NO

Monitored

Full

99990003

13

Nitrate

729 / 3

0.02

11.32

5.45

5.88

24

NO

Monitored

Full

99990003

13

pH

760 / 3

7.14

8.74

8.27

8.3

0

NO

Monitored

Full

Class HH - No Data

Monitoring and Methods
Assessment Key Dates
1/2/2018
Fixed Monitoring Start Date
12/31/2020
Fixed Monitoring End Date
Methods
210
Fixed station physical/chemical monitoring (conventional pollutants only)
270
PWS chemical monitoring (ambient water)
420
Indicator bacteria monitoring