2024 Pending assessment for Old Mans Creek

Old Mans Creek IA 02-IOW-686

from confluence with unnamed tributary (N line S1 T78N R7W Johnson Co.) to confluence with unnamed tributary in NE 1/4 S4 T78N R8W Johnson 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: 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Trend: Unknown

Created: 11/1/2023 8:12:56 AM
Updated: 2/1/2024 7:52:35 AM

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

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

Cause Magnitude

Moderate

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

Class BWW2

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 use remains assessed as "not supported" due to levels of indicator bacteria that violated state water quality criteria. The Class BWW2 use was assessed as "fully supported” based on biological sampling data and water quality monitoring data. Note: A TMDL covering the bacteria impairments for all segments, with the segment code prefix "IA 02-IOW" in the Iowa River Basin, was approved by EPA in 2018. Due to the completion of the TMDL, the IR category for the Class A1 use was changed from 5p (impaired; TMDL needed) to 4a (impaired; TMDL approved).

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	10520001	Old Mans Creek near Iowa City
Iowa DNR	6	BIO	See Below	1047	Old Mans Creek	Sharon Center
Iowa DNR	6	BIO	See Below	5	Old Mans Creek	Williamstown

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

10520001

8/8/8

779

448

764

YES

7 / 3

6 / 3

YES

Mon

Not

Presumptive 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
10520001	6	36 / 3	7.6	8.5	8.1	0	7	NO	Mon	Full

Class BWW2 - 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
10520001	6	Chloride	36 / 3	21	82	31	NA	0 / 0	7	NO	Mon	Full
10520001	6	Dissolved Oxygen	36 / 3	7.6	14.8	11.2	0	NA / NA	7	NO	Mon	Full
10520001	6	pH	36 / 3	7.6	8.5	8.1	0	NA / NA	7	NO	Mon	Full
10520001	6	Sulfate	36 / 3	14	88	28	0	NA / NA	7	NO	Mon	Full
10520001	6	Temperature	36 / 3	0.2	29.2	13.1	0	NA / NA	7	NO	Mon	Full

Class BWW2 - 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
10520001	6	Ammonia	36 / 3	0.21	0.04	0.02	0 / 0	NO	Mon	Full
10520001	6	Cadmium	20 / 3	0.5	0.5	0.5	0 / 0	NO	Mon	Full
10520001	6	Chromium	20 / 3	2	0.56	0.5	0 / 0	NO	Mon	Full
10520001	6	Lead	20 / 3	1	0.92	1	0 / 0	NO	Mon	Full
10520001	6	Nickel	20 / 3	3.4	1.9	1.9	0 / 0	NO	Mon	Full
10520001	6	Selenium	18 / 2	2	0.8	0.5	0 / 0	NO	Mon	Full
10520001	6	Silver	20 / 3	1	0.902	1	0 / 0	NO	Mon	Full
10520001	6	Zinc	20 / 3	3.1	1.1	0.5	0 / 0	NO	Mon	Full

Class BWW2 - 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
1047	8/7/20	210	47f	MS	Floating Art Sub	63	Good	51	Pass
5	9/18/19	138	47f	MS	Art Sub	52	Fair	51	Pass
1047	9/19/16	210	47f	MS	Floating Art Sub	64	Good	51	Pass

Fish:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	Riffle Stream?	FIBI score	FIBI Class	47f FIBI BIT	FIBI Pass/Fail
5	9/18/19	138	47f	MS	NA	53	Good	36	Pass
1047	9/22/16	210	47f	MS	NA	34	Fair	36	Fail
5	10/7/15	138	47f	MS	NA	38	Fair	36	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Monitored	Pass (3/3)	Full
Fish	Evaluated	Pass (2/3)	Full	1	Assessment was evaluated because the samples used to complete
Overall	Evaluated	Pass	Full		the assessment were not collected in the recent five year period.

Monitoring and Methods

Assessment Key Dates

9/18/2019	Biological Monitoring
8/7/2020	Biological Monitoring
1/6/2020	Monitoring Start
12/6/2022	Monitoring End
10/7/2015	Biological Monitoring
9/19/2016	Biological Monitoring
9/22/2016	Biological Monitoring
3/9/2018	TMDL Completed

Methods

150	Monitoring data more than 5 years old
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

Old Mans Creek IA 02-IOW-686

Assessment Summary

Assessment Explanation

Assessment Key Dates

Methods