Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Deer Creek IA 02-CED-591

mouth (S23 T99N R18W Mitchell Co.) to the Mitchell-Worth county line (west line S6 T100N R18W Mitchell 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
Declining
Trend Comment
New Class BWW2 benthic macroinvertebrate Category 5 impairment.
Created
10/27/2025 3:09:36 PM
Updated
12/1/2025 3:57:17 PM
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
Slight
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
Cycle Added
2008
Impairment Rationale
Geometric mean criterion exceeded
Data Source
Special project/study
TMDL Priority
Tier III
Class BWW2
Aquatic Life - Warm Water Type 2
Not Supported
Support Level
Not Supported
Impairment Code
5b-v - Biological - verified
Cause Magnitude
Moderate
Status
New
Source
Unknown: Source Unknown
Source Confidence
Low
Cycle Added
2026
Impairment Rationale
Low Biotic Index
Data Source
Biological monitoring: Iowa DNR WQMA
TMDL Priority
Tier IV
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The presumptive Class A1 use was assessed as “not supported" due to levels of indicator bacteria (E. coli) that slightly exceeded state criteria. The Class BWW2 use was assessed as “not supported” based on biological sampling data.

Assessment Explanation

Data Sources:

Data Source

Data Source ID

Data Type

Data Age

Site ID

Site Name

Site Description

CEDARMIT

21

WQ

CY 2016-2017

15660007

Deer Creek

At Dancer Ave

Iowa DNR

6

BIO

See Below

29

Deer Creek

Carpenter – 1 mi NW


Presumptive Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples / # Years

2016 Geometric Mean

2017 Geometric Mean

Annual Geometric Mean Violation

# Violations

% Violations

Significantly >10% Violations

Assessment Type

Support Level

15660007

21

14 / 2

166

168

Yes

8

57%

Yes

Evaluated

Not


Presumptive 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

15660007

21

14 / 2

8.4

8.3

8.3

0

0%

No

Evaluated

Full


Class BWW2 - Binomial 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

15660007

21

Dissolved oxygen

10 / 2

12.8

9.7

9.8

NA / 0

NA / 0%

No

Evaluated

Full

15660007

21

pH

14 / 2

8.4

8.3

8.3

0 / NA

0% / NA

No

Evaluated

Full

15660007

21

Temperature

14 / 2

23.8

15.8

16.9

0 / 0

0% / 0%

No

Evaluated

Full


Class BWW2 - Biological Sampling:


Benthic Macroinvertebrates:

BioNet Site ID

Date

Drainage Area (mi2)

Ecoregion

Major Drainage/Thermal

BM Sample Gear

BMIBI score

BMIBI Class

47c BMIBI BIT

BMIBI Pass/Fail

29

8/15/24

90.4

47c

MS/WW

Hess

41

Fair

70

Fail

29

9/8/23

90.4

47c

MS/WW

Surber

61

Good

70

Fail

29

7/21/21

90.4

47c

MS/WW

Hess

79

Excellent

70

Pass


Fish:

BioNet Site ID

Date

Drainage Area (mi2)

Ecoregion

Major Drainage/Thermal

Riffle Stream?

FIBI score

FIBI Class

47c FIBI BIT

FIBI Pass/Fail

29

7/21/21

90.4

47c

MS/WW

Yes

74

Excellent

65

Pass


Overall:

Community

Assessment Type

Assessment Result

Support Level

IR Category

Reason

Benthic Macroinvertebrates

Monitored

Fail (1/3)

Not

Fish

Evaluated

Pass (1/1)

Full

Assessment was monitored because the samples used for

Overall

Monitored

Fail

Not

5bv

the (BMIBI) assessment were collected in a recent five year period.

Monitoring and Methods
Assessment Key Dates
9/8/2023
Biological Monitoring
7/21/2021
Biological Monitoring
4/12/2016
Monitoring Start
10/17/2017
Monitoring End
8/15/2024
Biological Monitoring
Methods
150
Monitoring data more than 5 years old
200
Physical/Chemical Monitoring
315
Regional reference site approach
320
Benthic macroinvertebrate surveys
330
Fish surveys
420
Indicator bacteria monitoring