Iowa DNR
ADBNet

Water Quality Assessments

Impaired Waters List

Cedar River IA 02-CED-449

mouth (S20 T75N R4W Louisa Co.) to confluence with Sugar Cr. in S17 T78N R2W Muscatine Co.

Assessment Cycle
2022
Release Status
Final
Data Collection Period
Overall IR Category
5 - Water is impaired or threatened and a TMDL is needed.
Trend
Unknown
Created
12/20/2021 10:25:21 AM
Updated
1/13/2022 7:30:49 AM
Assessment conducted in accordance with Iowa's 2022 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
N/A
Cycle Added
2010
Impairment Rationale
Geometric mean criterion exceeded
Data Source
Ambient monitoring: Iowa DNR-rivers
TMDL Priority
Tier III
Class BWW1
WINOFI
Biological: low aquatic macroinvertebrate IBI
Support Level
Water in Need of Further Investigation (WINOFI)
Impairment Code
3b-u - Use potentially biologically impaired based on uncalibrated IBI metrics.
Cause Magnitude
Slight
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
Cycle Added
2018
Impairment Rationale
Low Biotic Index
Data Source
Biological monitoring: Iowa DNR WQMA
Class HH
Not Assessed
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 exceeded water quality criteria. The Class BWW1 use was assessed as "WINOFI” based on biological sampling data. All other designated uses were "not assessed." Note: This segment was not included in the 2010 EPA TMDL for indicator bacteria impairments in nine segments of Cedar River; therefore, this impairment is not covered by the TMDL and is considered appropriate for Category 5a 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 2018-2020

10700001

Cedar River near Conesville

Iowa DNR

6

BIO

See Below

849

Cedar River

Conesville

Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2018/ 2019/2020)

2018 Geometric Mean

2019 Geometric Mean

2020 Geometric Mean

Violates Annual Geometric Mean?

# 2018 SSM violations / SSM Violations needed for impairment

# 2019 SSM violations / SSM Violations needed for impairment

# 2020 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

10700001

6

8/8/8

72

130

59

YES

2 / 3

3 / 3

1 / 3

YES

Monitored

Not

Class A - 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

10700001

6

36 / 3

6.2

8.9

8.2

1

7

NO

Monitored

Full

Class BWW1 - Conventional 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

10700001

6

Ammonia

36 / 3

0.02

0.93

0.12

NA

0 / 0

7

NO

Monitored

Full

10700001

6

Chloride

36 / 3

14

53

26

NA

0 / 0

7

NO

Monitored

Full

10700001

6

Dissolved Oxygen

36 / 3

6.9

14.4

10.7

0

NA / NA

7

NO

Monitored

Full

10700001

6

pH

36 / 3

6.2

8.9

8.2

1

NA / NA

7

NO

Monitored

Full

10700001

6

Sulfate

36 / 3

15

60

26

0

NA / NA

7

NO

Monitored

Full

10700001

6

Temperature

36 / 3

0.1

29.1

12.5

0

NA / NA

7

NO

Monitored

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

10700001

6

Aluminum

14 / 3

6.9

1.3

0.5

0 / 0

NO

Monitored

Full

10700001

6

Arsenic

13 / 3

2.4

1.5

1.4

0 / 0

NO

Monitored

Full

10700001

6

Cadmium

13 / 3

0.09

0.04

0.02

0 / 0

NO

Monitored

Full

10700001

6

Chromium

13 / 3

1.1

0.8

0.8

0 / 0

NO

Monitored

Full

10700001

6

Lead

13 / 3

0.48

0.16

0.13

0 / 0

NO

Monitored

Full

10700001

6

Nickel

13 / 3

3.2

2.4

2.4

0 / 0

NO

Monitored

Full

10700001

6

Silver

13 / 3

0.025

0.025

0.025

0 / 0

NO

Monitored

Full

10700001

6

Zinc

13 / 3

3

2.05

2.3

0 / 0

NO

Monitored

Full

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID

Date

Drainage Area (mi2)

Ecoregion

Major Drainage

BM Sample Gear

BMIBI score

BMIBI Class

72d BMIBI BIT

BMIBI Pass/Fail

849

8/27/18

7789

72d

MS

Floating Art Sub

35

Fair

51

Fail


Overall:

Community

Assessment Type

Assessment Result

Support Level

IR Category

Reason

Benthic Macroinvertebrates

Evaluated

Fail (0/1)

Not

Assessment was evaluated because the drainage area of the sample site

Overall

Evaluated

Fail

WINOFI

3bu

was greater than the calibrated range.


Class HH – No Data

Monitoring and Methods
Assessment Key Dates
8/27/2018 Biological Monitoring
1/2/2018 Fixed Monitoring Start Date
12/9/2020 Fixed Monitoring End Date
Methods
230 Fixed station physical/chemical (conventional plus toxic pollutants)
315 Regional reference site approach
320 Benthic macroinvertebrate surveys
420 Indicator bacteria monitoring