Cedar River IA 02-CED-472

from W. Fk. Cedar R. (S4 T90N R14W Black Hawk Co.) to lowhead dam at Waverly in NW 1/4 S2 T91N R14W Bremer Co.

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 2020 - 2022
Stream/River Water Quality Data	CY 2020 - 2022
Lake Water Quality Data	CY 2018 - 2022
Biological Sampling Data	CY 2018 - 2022*
Fish Kill Data	CY 2018 - 2022
Fish Tissue Sampling Data	CY 2018 - 2022
Continuous Dissolved Oxygen Sampling Data	CY 2018 - 2022
*Biological sites sampled in both 2017 and 2021 were also assessed.

Open Segment Map
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Cycle: 2024
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 11/1/2023 8:12:25 AM
Updated: 1/17/2024 7:27:03 AM

Use Support

Class A1

Recreation - Primary contact

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

2008

Impairment Rationale

Single-sample maximum criterion exceeded in significantly > 10% of samples

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier III

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

Status

New

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2024

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 2020-2022 E. coli data suggest full support of the Class A1 use; however, delisting an impairment requires a monitored assessment. Therefore, the Category 5a Class A1 impairment will remain. The Class BWW1 use was assessed as "WINOFI” based on biological sampling data. The Class HH use was assessed as “fully supported” based on water quality monitoring data. Note: This segment was not included in the 2010 EPA TMDL for indicator bacteria impairments in nine segments of Cedar River.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2020-2022	10090001	Cedar River near Janesville
Iowa DNR	6	BIO	See Below	841	Cedar River	Janesville

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

10090001

8/8/8

1 / 3

Eval

Full

The 2020-2022 E. coli data suggest full support of the Class A1 use; however, delisting an impairment requires a monitored assessment. Therefore, the Category 5a Class A1 impairment will remain.

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
10090001	6	36 / 3	7.8	8.9	8.3	0	7	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
10090001	6	Chloride	36 / 3	14	43	25	NA	0 / 0	7	NO	Mon	Full
10090001	6	Dissolved Oxygen	36 / 3	6.4	15.8	11.4	0	NA / NA	7	NO	Mon	Full
10090001	6	pH	36 / 3	7.8	8.9	8.3	0	NA / NA	7	NO	Mon	Full
10090001	6	Sulfate	36 / 3	13	31	22	0	NA / NA	7	NO	Mon	Full
10090001	6	Temperature	36 / 3	0.2	26.9	11.9	0	NA / NA	7	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
10090001	6	Aluminum	21 / 3	880	301	150	0 / 0	NO	Mon	Full
10090001	6	Ammonia	36 / 3	0.57	0.08	0.02	0 / 0	NO	Mon	Full
10090001	6	Cadmium	20 / 3	0.5	0.5	0.5	0 / 0	NO	Mon	Full
10090001	6	Chromium	20 / 3	1.2	0.6	0.5	0 / 0	NO	Mon	Full
10090001	6	Lead	20 / 3	1	0.9	1	0 / 0	NO	Mon	Full
10090001	6	Nickel	20 / 3	2.5	1.1	1	0 / 0	NO	Mon	Full
10090001	6	Selenium	18 / 2	2	1	1	0 / 0	NO	Mon	Full
10090001	6	Silver	20 / 3	1	0.902	1	0 / 0	NO	Mon	Full
10090001	6	Zinc	20 / 3	2.1	1	0.5	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	47c BMIBI BIT	BMIBI Pass/Fail
841	8/15/22	1671.1	47c	MS	Hess	71	Good	70	Pass
841	8/20/19	1671.1	47c	MS	Hess	67	Good	70	Fail

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 the sample site
Overall	Evaluated	Fail	WINOFI	3bu	was greater than the calibrated range.

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
10090001	6	Selenium	18 / 2	2	1	1	6	NO	Mon	Full

Monitoring and Methods

Assessment Key Dates

1/9/2020

Monitoring Start

12/8/2022

Monitoring End

8/20/2019

Biological Monitoring

8/15/2022

Biological Monitoring

Methods

200

Physical/Chemical Monitoring

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

420

Indicator bacteria monitoring