2024 Pending assessment for Cedar Creek

Cedar Creek IA 04-LDM-1053

mouth (S33 T75N R17W Mahaska Co.) to confluence with North Cedar Cr. in S15 T74N R18W Marion Co.

Assessment Cycle

2024

Release Status

Pending

Data Collection Period

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.

Overall IR Category: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown

Created: 11/1/2023 8:12:58 AM
Updated: 12/29/2023 1:05:35 PM

Assessment conducted in accordance with Iowa's 2024 IR methodology.

Use Support

Class A1

Presumptive Use

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5p - Impairment occurs on a waterbody with a presumptive A1 or B(WW1) use.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier III

Class BWW1

Fully Supported

Class HH

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive 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 was assessed as "fully supported" based on biological sampling and on water quality monitoring data. The Class HH use was assessed as "fully supported" based on water quality monitoring data.

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	10630002	Cedar Creek near Bussey
Iowa DNR	6	BIO	See Below	915	Cedar Creek	Bussey

Presumptive 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

10630002

8/8/8

196

242

374

YES

3 / 3

2 / 3

3 / 3

YES

Mon

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
10630002	6	35 / 3	6.4	8.3	7.7	1	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
10630002	6	Chloride	36 / 3	5.6	61	11.6	NA	0 / 0	7	NO	Mon	Full
10630002	6	Dissolved Oxygen	36 / 3	6.6	14.1	10	0	NA / NA	7	NO	Mon	Full
10630002	6	pH	35 / 3	6.4	8.3	7.7	1	NA / NA	7	NO	Mon	Full
10630002	6	Sulfate	36 / 3	42	170	98	0	NA / NA	7	NO	Mon	Full
10630002	6	Temperature	36 / 3	0	29.3	13.1	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
10630002	6	Ammonia	35 / 3	0.19	0.05	0.02	0 / 0	NO	Mon	Full
10630002	6	Cadmium	20 / 3	0.5	0.5	0.5	0 / 0	NO	Mon	Full
10630002	6	Chromium	20 / 3	4	0.7	0.5	0 / 0	NO	Mon	Full
10630002	6	Lead	20 / 3	1	0.91	1	0 / 0	NO	Mon	Full
10630002	6	Nickel	20 / 3	9.1	4.5	3.7	0 / 0	NO	Mon	Full
10630002	6	Selenium	18 / 2	2	0.7	0.5	0 / 0	NO	Mon	Full
10630002	6	Silver	20 / 3	1	0.902	1	0 / 0	NO	Mon	Full
10630002	6	Zinc	20 / 3	10	2	1.4	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	40a BMIBI BIT	BMIBI Pass/Fail
915	8/15/19	374	40a	MS	Surber	42	Fair	41	Pass
915	8/18/16	374	40a	MS	Hess	46	Fair	41	Pass

Fish:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	Riffle Stream?	FIBI score	FIBI Class	40a FIBI BIT	FIBI Pass/Fail
915	8/18/16	374	40a	MS	NA	48	Fair	33	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Pass (2/2)	Full
Fish	Evaluated	Pass (1/1)	Full	1	Assessment was evaluated because the samples used to complete
Overall	Evaluated	Pass	Full		the assessment were not collected in a recent five-year period.

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
10630002	6	Selenium	18 / 2	2	0.7	0.5	12	NO	Mon	Full

Monitoring and Methods

Assessment Key Dates

1/6/2020	Monitoring Start
12/1/2022	Monitoring End
8/15/2019	Biological Monitoring
8/18/2016	Biological Monitoring

Methods

200	Physical/Chemical Monitoring
315	Regional reference site approach
320	Benthic macroinvertebrate surveys
330	Fish surveys
420	Indicator bacteria monitoring

Water Quality Assessments

Impaired Waters List

Cedar Creek IA 04-LDM-1053

Assessment Summary

Assessment Explanation

Assessment Key Dates

Methods