Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Little Bear Creek IA 02-IOW-705

mouth (S16 T80N R13W Poweshiek Co.) to confluence with unnamed tributary in SE 1/4 NW 1/4 S29 T80N R14W Poweshiek 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 8:12:48 AM
Updated
1/4/2024 6:54:16 PM
Use Support
Class A1
Recreation - Primary contact
Not Supported
Support Level
Not Supported
Impairment Code
4a - Pollutant-caused impairment. TMDL has been completed.
Cause Magnitude
High
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
Cycle Added
2014
Impairment Rationale
Geometric mean criterion exceeded
Data Source
Special project/study
Class BWW2
Aquatic Life - Warm Water Type 2
Not Supported
Support Level
Not Supported
Impairment Code
5b-t - Biological - tentative
Cause Magnitude
Slight
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
Low
Cycle Added
2008
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 that exceeded state water quality criteria. The Class BWW2 use was assessed as “not supported" based on biological sampling data. Note: A TMDL covering the bacteria impairments for all segments, with the segment code prefix "IA 02-IOW" in the Iowa River Basin, was approved by EPA in 2018. Due to the completion of the TMDL, the IR category for the presumptive Class A1 use was changed from 5p (impaired; TMDL needed) to 4a (impaired; TMDL approved). Because not all impairments identified for this segment are covered by the TMDL, this segment remains in Category 5 of Iowa's Integrated Report (impaired; TMDL needed).

Assessment Explanation

Data Sources:

Data Source

Data Source ID

Data Type

Data Age

Site ID

Site Name

Site Description

Iowa DNR

6

WQ

CY 2012-2014

15790004

Little Bear Creek at S Orchard

LB4

Iowa DNR

6

WQ

CY 2012-2014

15790006

Little Bear Creek at 285 Ave

LB6

Iowa DNR

6

BIO

See Below

523

Little Bear Creek

Brooklyn – REMAP #290


Presumptive Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples / # Years

2012 Geometric Mean

2013 Geometric Mean

2014 Geometric Mean

Annual Geometric Mean Violation

# Violations

% Violations

Significantly >10% Violations

Assessment Type

Support Level

15790004

6

25 / 3

1082

749

1105

Yes

24

96%

Yes

Evaluated

Not

15790006

6

25 / 3

1266

1283

1429

Yes

24

96%

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

15790004

6

20 / 2

8.4

7.8

7.8

0

0%

No

Evaluated

Full

15790006

6

20 / 2

8.2

7.8

7.9

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

15790004

6

Ammonia

10 / 1

0.2

0.09

0.07

0 / 0

0% / 0%

No

Evaluated

Full

15790006

6

Ammonia

10 / 1

0.24

0.1

0.05

0 / 0

0% / 0%

No

Evaluated

Full

15790004

6

Chloride

15 / 2

55

35

32

0 / 0

0% / 0%

No

Evaluated

Full

15790006

6

Chloride

15 / 2

55

35

33

0 / 0

0% / 0%

No

Evaluated

Full

15790004

6

Dissolved oxygen

20 / 2

14.9

8.2

7.7

NA / 2

NA / 10%

No

Evaluated

Full

15790006

6

Dissolved oxygen

20 / 2

15

8.5

8.1

NA / 1

NA / 5%

No

Evaluated

Full

15790004

6

pH

20 / 2

8.4

7.8

7.8

0 / NA

0% / NA

No

Evaluated

Full

15790006

6

pH

20 / 2

8.2

7.8

7.9

0 / NA

0% / NA

No

Evaluated

Full

15790004

6

Temperature

20 / 2

23.5

15.1

16.8

0 / 0

0% / 0%

No

Evaluated

Full

15790006

6

Temperature

20 / 2

23.1

15.2

16.8

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

47f BMIBI BIT

BMIBI Pass/Fail

523

8/24/10

44

47f

MS/WW

ArtSub

52

Fair

51

Pass

523

8/18/05

44

47f

MS/WW

Surber

39

Fair

51

Fail


Fish:

BioNet Site ID

Date

Drainage Area (mi2)

Ecoregion

Major Drainage/Thermal

Riffle Stream?

FIBI score

FIBI Class

47f FIBI BIT

FIBI Pass/Fail

523

8/24/10

44

47f

MS/WW

NA

35

Fair

36

Fail

523

8/18/05

44

47f

MS/WW

NA

34

Fair

36

Fail


Overall:

Community

Assessment Type

Assessment Result

Support Level

IR Category

Reason

Benthic Macroinvertebrates

Evaluated

Fail (1/2)

Not

Fish

Evaluated

Fail (0/2)

Not

Assessment was evaluated because it included

Overall

Evaluated

Fail

Not

5bt

samples not collected in a recent five-year period.

Monitoring and Methods
Assessment Key Dates
8/18/2005
Biological Monitoring
8/24/2010
Biological Monitoring
9/17/2012
Monitoring Start
10/15/2014
Monitoring End
3/9/2018
TMDL Completed
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