Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Iowa River IA 02-IOW-628

from Burlington St. dam in Iowa City (Johnson Co.) to Coralville Reservoir dam (Johnson Co.)

Assessment Cycle
2024
Release Status
Pending
Data Collection Period
Overall IR Category
2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.
Trend
Unknown
Created
11/1/2023 8:12:47 AM
Updated
2/12/2024 7:40:56 AM
Assessment conducted in accordance with Iowa's 2024 IR methodology.
Use Support
Class A1
Recreation
Primary contact
Fully Supported
Class BWW1
Aquatic Life
Warm Water Type 1
WINOFI
Support Level
Water in Need of Further Investigation (WINOFI)
Impairment Code
3b-u - Use potentially biologically impaired based on uncalibrated IBI metrics.
Cause Magnitude
Moderate
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
Low
Cycle Added
2008
Impairment Rationale
Potential Impairment
Data Source
Biological monitoring: Iowa DNR WQMA
Class C
Drinking Water
Fully Supported
Class HH
Human Health
Fully Supported
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The Class A1 use was assessed as "fully supported" based on water quality monitoring data. The Class BWW1 use was assessed as "WINOFI" based on biological sampling data. The Class C (drinking water) use was assessed as "fully supported" based on water quality monitoring data and drinking water compliance monitoring required by the DNR. The Class HH (fish consumption) use remains assessed as "fully supported" based on fish tissue sampling data. Note: A TMDL for indicator bacteria in this segment of Iowa River approved by EPA in June 2007. The approval of this TMDL moves the bacterial impairment for this segment from Iowa's list of Section 303(d) waters (Category 5a) to Category 4a (impaired; TMDL not required). Additionally, 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.

Assessment Explanation

Data Sources:

Data Source

Data Source ID

Data Type

Data Age

Site ID

Site Name

Site Description

USACE

12

WQ

CY 2020-2022

2222222

Iowa River (Downstream Coralville Reservoir)

PWS

27

WQ

CY 2020-2022

99990175

Iowa River

PWS

27

WQ

CY 2020-2022

99990176

Iowa River

Iowa DNR

6

BIO

See Below

941

Iowa River

Iowa City - US1

Iowa DNR

6

FT

See Below

1125

Iowa River at Iowa City


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

2222222

12

10/9/9

26

15

29

NO

1 / 3

0 / 3

2 / 3

NO

Mon

Full


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

2222222

12

60 / 3

7.3

8.6

8.1

0

10

NO

Mon

Full

99990175

27

5699 / 3

7

9.32

8.3

12

600

NO

Mon

Full

99990176

27

73 / 3

7.41

8.84

8.21

0

12

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

2222222

12

Dissolved Oxygen

60 / 3

5.95

15.41

10.2

0

NA / NA

10

NO

Mon

Full

2222222

12

pH

60 / 3

7.3

8.6

8.1

0

NA / NA

10

NO

Mon

Full

99990175

27

pH

5699 / 3

7

9.32

8.3

12

NA / NA

600

NO

Mon

Full

99990176

27

pH

73 / 3

7.41

8.84

8.21

0

NA / NA

12

NO

Mon

Full

2222222

12

Temperature

60 / 3

0.1

27.9

15.3

0

NA / NA

10

NO

Mon

Full

99990175

27

Temperature

5732 / 3

0.55556

30.1667

14.156

0

NA / NA

603

NO

Mon

Full

99990176

27

Temperature

77 / 3

-4

29

13

0

NA / NA

12

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

2222222

12

Ammonia

59 / 3

0.664

0.18

0.15

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

47f BMIBI BIT

BMIBI Pass/Fail

941

10/10/14

3158

47f

MS

Floating Art Sub

38

Fair

51

Fail

941

9/19/13

3158

47f

MS

Art Sub

20

Poor

51

Fail


Overall:

Community

Assessment Type

Assessment Result

Support Level

IR Category

Reason

Benthic Macroinvertebrates

Evaluated

Fail (0/2)

WINOFI

Assessment was evaluated because the drainage area of

Overall

Evaluated

Fail

WINOFI

3bu

the sample site was greater than the calibrated range.


Class C - Binomial Parameters:

Site ID

Data Source ID

Parameter Name

# Samples / # Years

Minimum Value

Maximum Value

Mean Value

Median Value

# Violations

Violates Significantly >10% Rule?

Assessment Type

Support Level

2222222

12

Inorganic nitrogen (nitrate and nitrite)

59 / 3

0.1

11.9

3.4

3

3

NO

Mon

Full

99990175

27

Nitrate

2698 / 3

0.05

13.8

3.2

3.3

18

NO

Mon

Full

99990176

27

Nitrate

146 / 3

0.13

12

3.39

3.12

5

NO

Mon

Full

2222222

12

pH

60 / 3

7.3

8.6

8.1

8.1

0

NO

Mon

Full

99990175

27

pH

5699 / 3

7

9.32

8.3

8.3

12

NO

Mon

Full

99990176

27

pH

73 / 3

7.41

8.84

8.21

8.21

0

NO

Mon

Full


Class C - Toxic Parameters:

Site ID

Data Source ID

Parameter Name

# Samples per Year (2020/ 2021/2022)

2020 Mean

2021 Mean

2022 Mean

# Non-Detects per Year (2020/ 2021/2022)

Support Level per Year (2020/ 2021/2022)

Assessment Type

Support Level

99990176

27

Alachlor

9/9/12

0

0

0

9/9/12

Full/Full/Full

Mon

Full

99990176

27

Atrazine

4/8/18

0

0

0.633

4/8/15

Full/Full/Full

Mon

Full

99990176

27

Simazine

9/9/12

0

0

0

9/9/12

Full/Full/Full

Mon

Full


Class C - Iowa Drinking Water Compliance Report:


Compliance monitoring required by the Iowa DNR Water Supply Operations and Engineering Sections did not show violations of finished water caused by source water at the Iowa City Water Department and University Water System facilities during the 2020-22 monitoring period. The results of compliance monitoring as reported in annual compliance reports are available at the following location at the Iowa DNR’s home page: https://www.iowadnr.gov/Environmental-Protection/Water-Quality/Water-Supply-Engineering/Annual-Compliance-Report.


Class HH - Fish Tissue Sampling:

Site ID

Biopart

Year

Species

# in sample / # of samples

Avg Length (cm)

(Avg) Hg (ppm)

Chlordane (ppm)

Sum PCBs (ppm)

1125

fillet

2015

common carp

5

48.8

0.09

0.02

0.06

1125

tissue plug

2015

white bass

5

35.6

0.05

Support Level

Full

Monitoring and Methods
Assessment Key Dates
1/1/2020
Monitoring Start
12/31/2022
Monitoring End
9/19/2013
Biological Monitoring
10/10/2014
Biological Monitoring
8/15/2015
Fish Tissue Monitoring
6/1/2007
TMDL Completed
3/9/2018
TMDL Completed
Methods
150
Monitoring data more than 5 years old
200
Physical/Chemical Monitoring
260
Fish tissue analysis
275
Drinking water compliance reports
315
Regional reference site approach
320
Benthic macroinvertebrate surveys
420
Indicator bacteria monitoring