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 2018 - 2020
Stream/River Water Quality Data	CY 2018 - 2020
Lake Water Quality Data	CY 2016 - 2020
Biological Sampling Data	CY 2016 - 2020*
Fish Kill Data	CY 2016 - 2020
Fish Tissue Sampling Data	CY 2016 - 2020
Continuous Dissolved Oxygen Sampling Data	CY 2016 - 2020
*Biological sites sampled in both 2015 and 2019 were also assessed.

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Cycle: 2022
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 12/8/2021 8:57:58 AM
Updated: 12/22/2021 6:54:45 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

Fully Supported

Class HH

Human Health -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed as "not supported" based on levels of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW1 use was assessed as "fully supported" based on biological sampling data. All other designated uses were "not assessed."

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2018-2020	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 (2018/ 2019/2020)

2018 Geometric Mean

2019 Geometric Mean

2020 Geometric Mean

Violates Annual Geometric Mean?

# 2018 SSM violations / SSM Violations needed for impairment

# 2019 SSM violations / SSM Violations needed for impairment

# 2020 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

10090001

7/8/8

385

141

YES

6 / 3

3 / 3

1 / 3

YES

Monitored

Not

Class A - 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	7.2	8.6	8.1	0	7	NO	Monitored	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
10090001	6	Ammonia	36 / 3	0.02	0.94	0.09	NA	0 / 0	7	NO	Monitored	Full
10090001	6	Chloride	36 / 3	10	30	20	NA	0 / 0	7	NO	Monitored	Full
10090001	6	Dissolved Oxygen	36 / 3	6.6	13.8	10.7	0	NA / NA	7	NO	Monitored	Full
10090001	6	pH	36 / 3	7.2	8.6	8.1	0	NA / NA	7	NO	Monitored	Full
10090001	6	Sulfate	36 / 3	5	31	19	0	NA / NA	7	NO	Monitored	Full
10090001	6	Temperature	36 / 3	0.3	26.9	11.2	0	NA / NA	7	NO	Monitored	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	14 / 3	2.2	0.6	0.3	0 / 0	NO	Monitored	Full
10090001	6	Arsenic	13 / 3	4.1	2.7	2.7	0 / 0	NO	Monitored	Full
10090001	6	Cadmium	13 / 3	0.06	0.03	0.02	0 / 0	NO	Monitored	Full
10090001	6	Chromium	13 / 3	1.1	0.8	0.8	0 / 0	NO	Monitored	Full
10090001	6	Lead	13 / 3	0.17	0.1	0.1	0 / 0	NO	Monitored	Full
10090001	6	Nickel	13 / 3	3.1	2.5	2.5	0 / 0	NO	Monitored	Full
10090001	6	Silver	13 / 3	0.025	0.025	0.025	0 / 0	NO	Monitored	Full
10090001	6	Zinc	13 / 3	2.6	1.8	1.9	0 / 0	NO	Monitored	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	8/20/19	1671	47c	MS	Hess	67	Good	70	Pass

Overall:

Community

Assessment Type

Assessment Result

Support Level

IR Category

Reason

Benthic Macroinvertebrates

Evaluated

Pass (1/1)

Full

The BMIBI score passed using the 8 point UAV applied to single samples.

Assessment was evaluated because the drainage area of the sample site

Overall

Evaluated

Pass

Full

was greater than the calibrated range.

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

1/8/2018

Fixed Monitoring Start Date

12/7/2020

Fixed Monitoring End Date

8/20/2019

Biological Monitoring

Methods

230

Fixed station physical/chemical (conventional plus toxic pollutants)

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

420

Indicator bacteria monitoring