Cedar River IA 02-CED-451

from Rock Run Cr. (S28 T80NR3W Cedar Co ) to Hwy 30 bridge at Cedar Rapids in S9 T82N R6W Linn Co.

This is a DRAFT assessment

Draft assessments may change without notice

Open Data Collection Period Modal

For purposes of developing stream/river water quality assessments for integrated reporting, three years of water quality data are typically used for both conventional pollutant parameters (e.g., indicator bacteria) and the less frequently monitored toxic parameters (e.g., toxic metals). Since the 2004 IR cycle, DNR has used a three-year data gathering period for streams, rivers, and beaches. For most assessments, the use of three years of data increases the number of samples upon which the decision on use support is based and helps address the problem of weather-related year-to-year fluctuations in water quality.

Due to the lower sampling frequency in Iowa’s ambient lake, biological, fish kill, and fish tissue monitoring programs, five years of data are used for developing IR assessments and for identifying Section 303(d) listings.

Data Type	Data Timeframe
Beach Sampling Data	CY 2022 - 2024
Stream/River Water Quality Data	CY 2022 - 2024
Lake Water Quality Data	CY 2020 - 2024
Biological Sampling Data	CY 2020 - 2024*
Fish Kill Data	CY 2020 - 2024
Fish Tissue Sampling Data	CY 2020 - 2024
Continuous Dissolved Oxygen Sampling Data	CY 2020 - 2024
*Biological sites sampled in both 2019 and 2023 were also assessed.

Open Segment Map
View 2026 assessment summary page

Cycle: 2026
Current Phase: Public Comment
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Stable
Created: 10/27/2025 3:09:38 PM
Updated: 2/11/2026 9:31:48 AM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

4a - Pollutant-caused impairment. TMDL has been completed.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2002

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

Class BWW1

Aquatic Life - Warm Water Type 1

Not Supported

Biological: loss of native mussel species

Support Level

Not Supported

Impairment Code

5b - Biological impairment or pollutant-caused fish kill - unknown source. No administrative action.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2004

Impairment Rationale

Loss of >50% of native mussel species

Data Source

Special project/study

TMDL Priority

Tier IV

Biological: low aquatic macroinvertebrate IBI

Support Level

Further Investigation Needed

Impairment Code

3b-u - Use potentially biologically impaired based on uncalibrated IBI metrics.

Cause Magnitude

Slight

Status

New

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2026

Impairment Rationale

Potential Impairment

Data Source

Biological monitoring: Iowa DNR WQMA

Class HH

Human Health -

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 (E. coli) that violated state water quality criteria. The Class BWW1 use remains assessed as "not supported" based on results of a 1998-99 statewide survey of freshwater mussels. The Class HH use was assessed as "fully supported" based on fish tissue sampling and water quality monitoring data. Note: A TMDL for indicator bacteria in this segment of Cedar River was prepared and approved by EPA in February 2010. The approval of this TMDL moved the bacteria impairment for this segment from Iowa's list of Section 303(d) waters (Category 5a of the IR) to IR Category 4a.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2022-2024	10570001	Cedar River near Cedar Rapids
Iowa DNR	6	WQ	CY 2022-2022	10570003	Cedar River at Palisades-Kepler State Park
Iowa DNR	6	BIO	See Below	952	Cedar River	Cedar Rapids - DS1
Iowa DNR	6	FT	See Below	1105	Cedar River	at Palisades Park
Iowa DNR	6	FT	See Below	1368	Cedar River (D)	West of Cedar Bluff

Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2022/ 2023/2024)

2022 Geometric Mean

2023 Geometric Mean

2024 Geometric Mean

Violates Annual Geometric Mean?

# 2022 SSM violations / SSM Violations needed for impairment

# 2023 SSM violations / SSM Violations needed for impairment

# 2024 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

10570001

1/8/8

153

YES

0 / NA

0 / 3

2 / 3

MONITORED

NOT

10570003

7/0/0

130

YES

1 / 3

MONITORED

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
10570001	6	28 / 3	7.9	9.3	8.4	3	6	NO	MONITORED	FULL
10570003	6	7 / 1	8.2	8.7	8.5	0	3	NO	EVALUATED	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
10570001	6	Chloride	29 / 3	18	90	38	NA	0 / 0	6	NO	MONITORED	FULL
10570003	6	Chloride	7 / 1	28	51	34	NA	0 / 0	3	NO	EVALUATED	FULL
10570001	6	Dissolved Oxygen	29 / 3	7.1	17.9	13	0	NA / NA	6	NO	MONITORED	FULL
10570003	6	Dissolved Oxygen	7 / 1	9.2	12.5	11	0	NA / NA	3	NO	EVALUATED	FULL
10570001	6	pH	28 / 3	7.9	9.3	8.4	3	NA / NA	6	NO	MONITORED	FULL
10570003	6	pH	7 / 1	8.2	8.7	8.5	0	NA / NA	3	NO	EVALUATED	FULL
10570001	6	Sulfate	29 / 3	17	77	35	0	NA / NA	6	NO	MONITORED	FULL
10570003	6	Sulfate	7 / 1	20	48	28	0	NA / NA	3	NO	EVALUATED	FULL
10570001	6	Temperature	29 / 3	0.2	29.2	12.1	0	NA / NA	6	NO	MONITORED	FULL
10570003	6	Temperature	7 / 1	6.9	28	19.4	0	NA / NA	3	NO	EVALUATED	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
10570001	6	Aluminum	11 / 2	9300	1019	90	1 / 1	NO	MONITORED	FULL
10570003	6	Aluminum	7 / 1	1500	596	410	0 / 1	NO	EVALUATED	FULL
10570001	6	Ammonia	28 / 3	0.99	0.12	0.04	0 / 0	NO	MONITORED	FULL
10570003	6	Ammonia	7 / 1	0.61	0.18	0.09	0 / 0	NO	EVALUATED	FULL
10570001	6	Cadmium	11 / 2	0.5	0.5	0.5	0 / 0	NO	MONITORED	FULL
10570003	6	Cadmium	7 / 1	0.5	0.5	0.5	0 / 0	NO	EVALUATED	FULL
10570001	6	Chromium	11 / 2	12	2.59	0.78	0 / 1	NO	MONITORED	FULL
10570003	6	Chromium	7 / 1	2	0.8	0.6	0 / 0	NO	EVALUATED	FULL
10570001	6	Copper	18 / 2	24	2.5	1.1	0 / 1	NO	MONITORED	FULL
10570003	6	Copper	7 / 1	1.6	0.7	0.6	0 / 0	NA	EVALUATED	NA
10570001	6	Lead	11 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10570003	6	Lead	7 / 1	1	1	1	0 / 0	NO	EVALUATED	FULL
10570001	6	Nickel	11 / 2	1.6	1.2	1.1	0 / 0	NO	MONITORED	FULL
10570003	6	Nickel	7 / 1	1.4	1	1.1	0 / 0	NO	EVALUATED	FULL
10570001	6	Selenium	29 / 3	2	1	1	0 / 0	NO	MONITORED	FULL
10570003	6	Selenium	7 / 1	2	1.1	1	0 / 0	NO	EVALUATED	FULL
10570001	6	Silver	11 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10570003	6	Silver	7 / 1	1	1	1	0 / 0	NO	EVALUATED	FULL
10570001	6	Zinc	11 / 2	3.8	1.5	1.4	0 / 0	NO	MONITORED	FULL
10570003	6	Zinc	7 / 1	3.1	1.3	1	0 / 0	NO	EVALUATED	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
952	8/19/23	6955	47f	MS	Floating Art Sub	27	Poor	51	Fail
952	8/30/19	6955	47f	MS	Floating Art Sub	65	Good	51	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (1/2)	WINOFI		Assessment was evaluated because the drainage area of
Overall	Evaluated	Fail	WINOFI	3bu	the sample site was greater than the calibrated range.

Class BWW1 – Freshwater Mussel Sampling:

Freshwater Mussel Survey	Avg. # Freshwater Mussel Species	Avg. # Freshwater Mussel Species Increase/Decrease	Avg % Freshwater Mussel Species Increase/Decrease	Assessment Type	Support Level	IR Category
1984-85 (Frest 1987) 5 sites	5.6
1998-99 (Arbuckle et al. 2000) 5 sites	0.4	-5	-92%	Evaluated	Not	5b
As presented by Arbuckle et al. (2000), the potential causes of declines in species richness of Iowa's freshwater mussels include siltation, destabilization of stream substrate, stream flow instability, and high instream levels of nutrients (phosphorus and nitrogen). Their study also suggested the importance of stream shading provided by riparian vegetation to mussel species richness.

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)
1105	tissue plug	2021	smallmouth bass	20	27.1	0.156
1368	tissue plug	2020	channel catfish	15	46.1	0.086
1368	tissue plug	2020	flathead catfish	10	44.1	0.167
1368	tissue plug	2020	shovelnose sturgeon	16	59.8	0.142
1368	tissue plug	2020	walleye	5	40	0.205
Support Level	Full

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
10570003	6	Cadmium	7 / 1	0.5	0.5	0.5	7	NA	EVALUATED	NA
10570003	6	Chromium	7 / 1	2	0.8	0.6	2	NA	EVALUATED	NA
10570003	6	Chromium (VI)	7 / 1	2	0.8	0.6	2	NA	EVALUATED	NA
10570001	6	Copper	18 / 2	24	2.5	1.1	6	NO	MONITORED	FULL
10570003	6	Copper	7 / 1	1.6	0.7	0.6	3	NA	EVALUATED	NA
10570003	6	Selenium	7 / 1	2	1.1	1	3	NO	EVALUATED	FULL
Site ID	Data Source ID	Parameter Name	# Samples per Year (2022/ 2023/2024)	2022 Mean	2023 Mean	2024 Mean	# Non-Detects per Year (2022/ 2023/2024)	Support Level per Year (2022/ 2023/2024)	Assessment Type	Support Level
10570001	6	Selenium	5/12/12	1.4	0.75	1.15	2/6/4	FS/FS/FS	MONITORED	FULL

Monitoring and Methods

Assessment Key Dates

9/30/1999

Biological Monitoring

8/30/2019

Biological Monitoring

2/1/2010

TMDL Completed

8/30/1984

Biological Monitoring

7/1/2020

Fish Tissue Monitoring

1/3/2022

Monitoring Start

12/2/2024

Monitoring End

7/7/2021

Fish Tissue Monitoring

8/19/2023

Biological Monitoring

Methods

120

Surveys of fish and game biologists/other professionals

150

Monitoring data more than 5 years old

200

Physical/Chemical Monitoring

260

Fish tissue analysis

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

420

Indicator bacteria monitoring