DRAFT 2026 assessment for Cedar River

Cedar River IA 02-CED-452

from Hwy 30 bridge at Cedar Rapids (S9 T82N R6W Linn Co) to confluence with Prairie Cr. in the SE 1/4 S34 T83N R7W Linn Co.

This is a DRAFT assessment

Draft assessments may change without notice

2026
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

Overall IR

4 - Water is impaired or threatened and a TMDL has been completed or is not needed.

Trend

Stable

Current Phase

Public Comment

Created

10/27/2025 3:08:50 PM by

Updated

12/29/2025 8:39:14 AM by

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

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2004

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

Class BWW1

Aquatic Life - Warm Water Type 1

WINOFI

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

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2008

Impairment Rationale

Potential Impairment

Data Source

Biological monitoring: Iowa DNR WQMA

Class HH

Human Health -

Fully Supported

303(d) Delistings for this Cycle

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use remains assessed as "not supported" due to historic levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The Class BWW1 use remains assessed as “WINOFI” based on the historic biological sampling data. The Class HH (fish consumption) use remains assessed as “fully supported” based on historic fish tissue sampling 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 bacterial 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 2014-16	10570001	Cedar River DS of Cedar Rapids (DS1)	Site located in Seg. 451 and no longer used for this segment.
Iowa DNR	6	BIO	See Below	503	Cedar River	Bertram – REMAP #185
Iowa DNR	6	FT	See Below	1016	Cedar River	At Cedar Rapids

Class A1 - Indicator Bacteria: 2014-2016

Site ID	Data Source ID	# Samples / # Years	2014 Geometric Mean	2015 Geometric Mean	2016 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
10570001	6	23 / 3	131	277	233	Yes	10	43%	Yes	Evaluated	Not

Class BWW1 - Biological Sampling: 2005

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	BM Sample Gear	BMIBI score	BMIBI Class	47f BMIBI BIT	BMIBI Pass/Fail
503	10/10/05	6829	47f	MS/WW	ArtSub	47	Fair	51	Fail
503	9/1/05	6829	47f	MS/WW	ArtSub	19	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 HH - Fish Tissue Sampling:

Site ID	Biopart	Year	Species	# in sample / # of samples	Avg Length (cm)	(Avg) Hg (ppm)	Chlordane (ppm)	Sum PCBs (ppm)
1016	fillet	2016	channel catfish	3	42.6	0.12	0.02	0.06
1016	tissue plug	2015	largemouth bass	5	32.9	0.05
Support Level	Full

Monitoring and Methods

Assessment Key Dates

9/1/2005

Biological Monitoring

10/10/2005

Biological Monitoring

8/3/2015

Fish Tissue Monitoring

1/2/2014

Monitoring Start

12/8/2016

Monitoring End

8/16/2016

Fish Tissue Monitoring

2/1/2010

TMDL Completed

Methods

150

Monitoring data more than 5 years old

260

Fish tissue analysis

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

420

Indicator bacteria monitoring