Iowa DNR
ADBNet

Water Quality Assessments

Impaired Waters List

Little Sioux River IA 06-LSR-1578

from confluence with Milford Cr. (NW 1/4 S14 T98N R37W Dickinson Co.) to confluence with West Fork Little Sioux R. in S36 T100N R38W Dickinson Co.

Assessment Cycle
2024
Release Status
Pending
Data Collection Period
Overall IR Category
5 - Water is impaired or threatened and a TMDL is needed.
Trend
Stable
Created
11/1/2023 8:13:04 AM
Updated
12/22/2023 10:11:35 AM
Assessment conducted in accordance with Iowa's 2024 IR methodology.
Use Support
Class A1
Not Supported
Bacteria: Indicator Bacteria- E. coli
Support Level
Not Supported
Impairment Code
5a - Pollutant-caused impairment. TMDL needed.
Cause Magnitude
Slight
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
Low
Cycle Added
2008
Impairment Rationale
Geometric mean criterion exceeded
Data Source
Ambient monitoring: Iowa DNR-rivers
TMDL Priority
Tier III
Class BWW1
Not Supported
Biological: low fish IBI
Support Level
Not Supported
Impairment Code
5b-t - Biological - tentative
Cause Magnitude
Slight
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
Low
Cycle Added
2022
Impairment Rationale
Low Biotic Index
Data Source
Biological monitoring: Iowa DNR WQMA
TMDL Priority
Tier IV
Class HH
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 that violated state water quality criteria. The Class BWW1 was assessed as "not supported” based 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

10300001

Little Sioux River near Milford

Iowa DNR

6

BIO

See Below

63

Little Sioux River

Horseshoe Bend County Park - Milford

Iowa DNR

6

BIO

See Below

1148

Little Sioux River

Gravel Road Bridge W of Milford


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

10300001

6

8/8/7

219

624

558

YES

4 / 3

6 / 3

6 / 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

10300001

6

36 / 3

6.8

8.5

7.9

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

10300001

6

Chloride

36 / 3

11

34

19

NA

0 / 0

7

NO

Mon

Full

10300001

6

Dissolved Oxygen

36 / 3

5.3

15.3

9.5

0

NA / NA

7

NO

Mon

Full

10300001

6

pH

36 / 3

6.8

8.5

7.9

0

NA / NA

7

NO

Mon

Full

10300001

6

Sulfate

36 / 3

26

190

97

0

NA / NA

7

NO

Mon

Full

10300001

6

Temperature

36 / 3

0

26.8

11

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

10300001

6

Ammonia

36 / 3

0.44

0.07

0.02

0 / 0

NO

Mon

Full

10300001

6

Cadmium

20 / 3

0.5

0.5

0.5

0 / 0

NO

Mon

Full

10300001

6

Chromium

20 / 3

3

0.92

0.72

0 / 0

NO

Mon

Full

10300001

6

Lead

20 / 3

1

0.91

1

0 / 0

NO

Mon

Full

10300001

6

Nickel

20 / 3

3.2

2.2

2

0 / 0

NO

Mon

Full

10300001

6

Selenium

18 / 2

5

2.5

2

0 / 0

NO

Mon

Full

10300001

6

Silver

20 / 3

1

0.902

1

0 / 0

NO

Mon

Full

10300001

6

Zinc

20 / 3

13

1.4

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

47b BMIBI BIT

BMIBI Pass/Fail

1148

7/19/21

484.0

47b

MO

Art Sub

53

Good

62

Fail

63

8/4/20

333.4

47b

MO

Surber

65

Good

62

Pass

1148

8/5/17

484.0

47b

MO

Floating Art Sub

73

Good

62

Pass


Fish:

Site ID

Date

Drainage Area (mi2)

Ecoregion

Major Drainage

Riffle Stream?

FIBI score

FIBI Class

47b FIBI BIT

FIBI Pass/Fail

63

8/4/20

333.4

47b

MO

Yes

51

Good

53

Fail


Overall:

Community

Assessment Type

Assessment Result

Support Level

IR Category

Reason

Benthic Macroinvertebrates

Monitored

Pass (2/3)

Full

Fish

Evaluated

Fail (0/1)

Not

Assessment was evaluated because the FIBI

Overall

Evaluated

Fail

Not

5bt

assessment was based on a single sample.


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

10300001

6

Selenium

18 / 2

5

2.5

2

3

NO

Mon

Full

Monitoring and Methods
Assessment Key Dates
7/19/2021 Biological Monitoring
8/4/2020 Biological Monitoring
8/15/2017 Biological Monitoring
1/8/2020 Monitoring Start
12/14/2022 Monitoring End
Methods
200 Physical/Chemical Monitoring
315 Regional reference site approach
320 Benthic macroinvertebrate surveys
330 Fish surveys
420 Indicator bacteria monitoring