Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Robin Creek IA 01-NEM-6373

from mouth (SW1/4 S14 T78N R3E Scott Co.) to headwaters in SW1/4 S10 T78N R3E Scott Co.

This is a DRAFT assessment
Draft assessments may change without notice
Cycle
2026
Current Phase
Public Comment
Overall IR
5 - Water is impaired or threatened and a TMDL is needed.
Trend
Unknown
Created
10/27/2025 3:11:31 PM
Updated
12/12/2025 11:06:50 AM
Use Support
Class A1
Recreation - Primary contact
Not Supported
Support Level
Not Supported
Impairment Code
5p - Impairment occurs on a waterbody with a presumptive A1 or B(WW1) use.
Cause Magnitude
Moderate
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
Cycle Added
2010
Impairment Rationale
Geometric mean criterion exceeded
Data Source
TMDL monitoring: Iowa DNR
TMDL Priority
Tier III
Class BWW1
Aquatic Life - Warm Water Type 1
Fully Supported
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The presumptive Class A1 use remains assessed as "not supported" due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The presumptive class BWW1 use was assessed as "fully supported" based on water quality data. Note: A TMDL for the bacterial impairment for streams in the Duck Creek basin was prepared by Iowa DNR in March 2010 and was approved by U.S. EPA in 2011. According to U.S. EPA, however, the TMDL for the Duck Creek watershed does not assign the required elements to Robin Creek; thus, this stream remains Section 303(d) impaired and in Category 5p of Iowa's Integrated Report.

Assessment Explanation

Data Sources:

Data Source

Data Source ID

Data Type

Data Age

Site ID

Site Name

Site Description

Iowa DNR

6

WQ

CY 2008

11820007

Robin Creek site along W 35th st. (RC1A)

Iowa DNR

6

WQ

CY 2013

11820010

Robin Creek (rc1a)

Iowa DNR

6

WQ

CY 2024

11820007

Robin Creek site along W 35th st. (RC1A)


Presumptive Class A1 - Indicator Bacteria: Historical

Site ID

Data Source ID

# Samples / # Years

2008 Geometric Mean

2013 Geometric Mean

Annual Geometric Mean Violation

# Violations

% Violations

Significantly >10% Violations

Assessment Type

Support Level

11820007

6

29 / 1

1308

NA

Yes

26

90%

Yes

Evaluated

Not

11820010

6

6 / 1

NA

895

Yes

4

67%

Yes

Evaluated

Not


Presumptive Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2022/ 2023/2024)

2022 Geometric Mean

2023 Geometric Mean

2024 Geometric Mean

Violates Annual Geometric Mean?

# 2022 SSM violations / SSM Violations needed for impairment

# 2023 SSM violations / SSM Violations needed for impairment

# 2024 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

11820007

6

0/0/15

NA

NA

737

YES

NA

NA

12 / 4

YES

MONITORED

NOT

Presumptive 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

11820007

6

16 / 1

7.3

8.6

7.8

0

4

NO

MONITORED

FULL

Presumptive 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

11820007

6

Dissolved Oxygen

16 / 1

4.3

14.7

9

1

NA / NA

4

NO

MONITORED

FULL

11820007

6

pH

16 / 1

7.3

8.6

7.8

0

NA / NA

4

NO

MONITORED

FULL

11820007

6

Temperature

16 / 1

6.57

27.78

18.59

0

NA / NA

4

NO

MONITORED

FULL

Monitoring and Methods
Assessment Key Dates
4/8/2008
Monitoring Start
10/28/2008
Monitoring End
5/19/2013
Monitoring Start
11/20/2013
Monitoring End
3/28/2024
Monitoring Start
10/10/2024
Monitoring End
Methods
150
Monitoring data more than 5 years old
200
Physical/Chemical Monitoring
420
Indicator bacteria monitoring