Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Morgan Creek IA 02-CED-513

mouth (S14 T83N R8W Linn Co.) to confluence with unnamed tributary in SW 1/4 S22 T83N R8W Linn 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 8:13:18 AM
Updated
1/11/2024 1:28:49 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
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
TMDL Priority
Tier III
Class BWW2
Aquatic Life - Warm Water Type 2
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 violations of Iowa water quality criteria for indicator bacteria (E. coli). The Class BWW2 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

CRWQ

23

WQ

CY 2020-2022

99990089

Morgan Creek

USGS

11

WQ

CY 2020-2022

5464475

Morgan Creek near Covington, IA


Presumptive 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

99990089

23

5/5/5

413

191

258

YES

3 / NA

3 / NA

3 / NA

YES

Eval

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

5464475

11

47 / 3

7.5

8.7

8

0

8

NO

Mon

Full

99990089

23

15 / 3

7.74

8.51

8.1

0

4

NO

Mon

Full


Class BWW2 - 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

5464475

11

Chloride

13 / 2

34.9

198

53.9

NA

0 / 0

4

NO

Mon

Full

99990089

23

Chloride

15 / 3

25.7

39.7

32.5

NA

0 / 0

4

NO

Mon

Full

5464475

11

Dissolved Oxygen

35 / 3

6.8

15.2

11.1

0

NA / NA

7

NO

Mon

Full

99990089

23

Dissolved Oxygen

14 / 3

7.6

15.3

10.9

0

NA / NA

4

NO

Mon

Full

5464475

11

pH

47 / 3

7.5

8.7

8

0

NA / NA

8

NO

Mon

Full

99990089

23

pH

15 / 3

7.74

8.51

8.1

0

NA / NA

4

NO

Mon

Full

5464475

11

Sulfate

13 / 2

26.9

51.9

37.9

0

NA / NA

4

NO

Mon

Full

99990089

23

Sulfate

15 / 3

22.4

44.4

32.7

0

NA / NA

4

NO

Mon

Full

5464475

11

Temperature

35 / 3

0

24.4

9.6

0

NA / NA

7

NO

Mon

Full

99990089

23

Temperature

15 / 3

7.6

24.3

18.2

0

NA / NA

4

NO

Mon

Full


Class BWW2 - 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

5464475

11

Ammonia

31 / 3

0.37

0.04

0.03

0 / 0

NO

Mon

Full



Monitoring and Methods
Assessment Key Dates
1/27/2020
Monitoring Start
12/20/2022
Monitoring End
Methods
200
Physical/Chemical Monitoring
420
Indicator bacteria monitoring
860
Other Agencies/Organizations provided monitoring data