Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

South Raccoon River IA 04-RAC-1181

mouth (S21 T78 R27W Dallas Co.) to confluence with Middle Raccoon R. in S9 T78N R29W near Redfield in Dallas Co

Cycle
2024
Release Status
Final
Overall IR
5 - Water is impaired or threatened and a TMDL is needed.
Trend
Unknown
Created
11/1/2023 8:12:59 AM
Updated
12/29/2023 1:17:02 PM
Use Support
Class A1
Recreation - Primary contact
Not Supported
Support Level
Not Supported
Impairment Code
5a - Pollutant-caused impairment. TMDL needed.
Cause Magnitude
Moderate
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
Cycle Added
2008
Impairment Rationale
Geometric mean criterion exceeded
Data Source
Ambient monitoring: Iowa DNR-rivers
TMDL Priority
Tier III
Class BWW1
Aquatic Life - Warm Water Type 1
Fully Supported
Class HH
Human Health -
Fully Supported
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The Class A1 use was assessed as "not supported" due to levels of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW1 use was assessed as "fully supported” based on water quality monitoring data and on biological sampling data. The Class HH use was assessed as "fully supported” based on water quality monitoring data.

Assessment Explanation

Data Sources:

Data Source

Data Source ID

Data Type

Data Age

Site ID

Site Name

Site Description

Iowa DNR

6

WQ

CY 2020-2022

10250001

South Raccoon River near Redfield

Iowa DNR

6

BIO

See Below

930

South Raccoon River

Nations Bridge County Park - Stuart


Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2020/ 2021/2022)

2020 Geometric Mean

2021 Geometric Mean

2022 Geometric Mean

Violates Annual Geometric Mean?

# 2020 SSM violations / SSM Violations needed for impairment

# 2021 SSM violations / SSM Violations needed for impairment

# 2022 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

10250001

6

8/8/8

330

138

492

YES

3 / 3

2 / 3

4 / 3

YES

Mon

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

10250001

6

36 / 3

7.3

8.6

8.2

0

7

NO

Mon

Full


Class BWW1 - Binomial 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

10250001

6

Chloride

36 / 3

12

28

19

NA

0 / 0

7

NO

Mon

Full

10250001

6

Dissolved Oxygen

36 / 3

7.8

14.7

10.9

0

NA / NA

7

NO

Mon

Full

10250001

6

pH

36 / 3

7.3

8.6

8.2

0

NA / NA

7

NO

Mon

Full

10250001

6

Sulfate

36 / 3

16

40

28

0

NA / NA

7

NO

Mon

Full

10250001

6

Temperature

36 / 3

0

29.8

12.5

0

NA / NA

7

NO

Mon

Full


Class BWW1 - Toxic Parameters:

Site ID

Data Source ID

Parameter Name

# Samples / # Years

Maximum Value

Mean Value

Median Value

# Acute / Chronic Violations

>1 Acute / Chronic Violation

Assessment Type

Support Level

10250001

6

Ammonia

36 / 3

0.38

0.06

0.02

0 / 0

NO

Mon

Full

10250001

6

Cadmium

20 / 3

0.5

0.5

0.5

0 / 0

NO

Mon

Full

10250001

6

Chromium

20 / 3

2

0.6

0.5

0 / 0

NO

Mon

Full

10250001

6

Lead

20 / 3

1

0.91

1

0 / 0

NO

Mon

Full

10250001

6

Nickel

20 / 3

4

1.49

1.4

0 / 0

NO

Mon

Full

10250001

6

Selenium

18 / 2

4

1.6

2

0 / 0

NO

Mon

Full

10250001

6

Silver

20 / 3

1

0.902

1

0 / 0

NO

Mon

Full

10250001

6

Zinc

20 / 3

2.9

0.8

0.5

0 / 0

NO

Mon

Full


Class BWW1 - Biological Sampling:


Benthic Macroinvertebrates:

Site ID

Date

Drainage Area (mi2)

Ecoregion

Major Drainage

BM Sample Gear

BMIBI score

BMIBI Class

47f BMIBI BIT

BMIBI Pass/Fail

930

7/17/19

988

47f

MS

Floating Art Sub

76

Excellent

51

Pass


Overall:

Community

Assessment Type

Assessment Result

Support Level

IR Category

Reason

Benthic Macroinvertebrates

Evaluated

Pass (1/1)

Full

Assessment was evaluated because the drainage area

Overall

Evaluated

Pass

Full

1

of the site is greater than the calibrated range.


Class HH-F - Toxic Parameters:

Site ID

Data Source ID

Parameter Name

# Samples / # Years

Maximum Value

Mean Value

Median Value

Number of Non - Detects

Mean Value > Criterion or MCL

Assessment Type

Support Level

10250001

6

Selenium

18 / 2

4

1.6

2

3

NO

Mon

Full

Monitoring and Methods
Assessment Key Dates
1/7/2020
Monitoring Start
12/5/2022
Monitoring End
7/17/2019
Biological Monitoring
Methods
200
Physical/Chemical Monitoring
315
Regional reference site approach
320
Benthic macroinvertebrate surveys
420
Indicator bacteria monitoring