2020 Final 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

2020

Release Status

Final

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 2016 - 2018
Stream/River Water Quality Data	CY 2016 - 2018
Lake Water Quality Data	CY 2014 - 2018
Biological Sampling Data	CY 2014 - 2018*
Fish Kill Data	CY 2014 - 2018
Fish Tissue Sampling Data	CY 2014 - 2018
Continuous Dissolved Oxygen Sampling Data	CY 2014 - 2018
*Biological sites sampled in both 2013 and 2017 were also assessed.

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

Created: 9/3/2020 12:58:44 PM
Updated: 10/12/2020 1:08:01 PM

Assessment conducted in accordance with Iowa's 2020 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

Delisted

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Cycle Delisted

2020

Delisting Rationale

TMDL preparation and approval

Data Source

Ambient monitoring: Iowa DNR-rivers

Class BWW2

Partially Supported

Biological: low fish IBI

Support Level

Partially Supported

Impairment Code

5b-t - Biological - tentative

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2006

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

TMDL Priority

Tier IV

General Use

Not Assessed

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 remains assessed as "partially supported” based on biological sampling 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). Because not all impairments identified for this segment are covered by the TMDL, this segment remains in Category 5 of Iowa's Integrated Report (impaired; TMDL needed).

Assessment Explanation

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2016-2018	10520001	Old Mans Creek nr Iowa City
Iowa DNR	6	BIO	See Below	5	Old Mans Creek	Williamstown
Iowa DNR	6	BIO	See Below	1047	Old Mans Creek	Sharon Center

Presumptive Class A1 - Indicator Bacteria:

Site ID	Data Source ID	# Samples / # Years	2016 Geometric Mean	2017 Geometric Mean	2018 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
10520001	6	16 / 3	1636.65	1070.75	199.57	Yes	13	81%	Yes	Monitored	Not

Presumptive Class A1 - pH:

Site ID	Data Source ID	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
10520001	6	36 / 3	8.3	7.9	8	0	0%	No	Monitored	Full

Class BWW2 - Conventional Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	% Acute/ Chronic Violations	Significantly >10% Violations	Assessment Type	Support Level
10520001	6	Ammonia	36 / 3	0.8	0.09	0.02	0 / 0	0% / 0%	No	Monitored	Full
10520001	6	Chloride	36 / 3	57	27	24	0 / 0	0% / 0%	No	Monitored	Full
10520001	6	Dissolved oxygen	36 / 3	13.8	9.7	9.1	NA / 2	NA / 6%	No	Monitored	Full
10520001	6	pH	36 / 3	8.3	7.9	8	0 / NA	0% / NA	No	Monitored	Full
10520001	6	Sulfate	36 / 3	55	24.4	21	0 / NA	0% / NA	No	Monitored	Full
10520001	6	Temperature	36 / 3	26.8	11.3	10.6	0 / 0	0% / 0%	No	Monitored	Full

Class BWW2 - Biological Sampling:

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
1047	9/19/16	210	47f	MS/WW	Float ArtSub	64	Good	51	Pass
5	10/7/15	138	47f	MS/WW	ArtSub	48	Fair	51	Fail
1047	9/8/15	210	47f	MS/WW	Float ArtSub	69	Good	51	Pass

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	Riffle Stream?	FIBI score	FIBI Class	47f FIBI BIT	FIBI Pass/ Fail
1047	9/22/16	210	47f	MS/WW	NA	34	Fair	36	Fail
5	10/7/15	138	47f	MS/WW	NA	38	Fair	36	Pass
5	10/11/10	138	47f	MS/WW	NA	24	Poor	36	Fail

Overall:

Community	Assessment Type	Assessment Result	Support Level	Earned IR Category	Actual IR Category	Reason
Benthic Macroinvertebrates	Monitored	Pass (2/3)	Full
Fish	Evaluated	Fail (1/3)	Partial
Overall	Evaluated	Fail	Partial	3bc	5bt	Assessment is evaluated because it included samples not collected in the last five years.

Class BWW2 - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	% Acute/ Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
10520001	6	Aluminum	9 / 2	8.3	1.867	0.32	0 / 0	0% / 0%	No	Evaluated	Full
10520001	6	Arsenic	9 / 2	1.9	1.33	1.4	0 / 0	0% / 0%	No	Evaluated	Full
10520001	6	Cadmium	9 / 2	0.05	0.028	0.025	0 / 0	0% / 0%	No	Evaluated	Full
10520001	6	Chromium	9 / 2	0.99	0.72	0.79	0 / 0	0% / 0%	No	Evaluated	Full
10520001	6	Copper	9 / 2	2.8	1.135	0.99	0 / 0	0% / 0%	No	Evaluated	Full
10520001	6	Lead	9 / 2	0.26	0.089	0.11	0 / 0	0% / 0%	No	Evaluated	Full
10520001	6	Nickel	9 / 2	5.4	3.4	3.6	0 / 0	0% / 0%	No	Evaluated	Full
10520001	6	Selenium	9 / 2	1.4	0.87	1	0 / 0	0% / 0%	No	Evaluated	Full
10520001	6	Zinc	9 / 2	4.8	1.98	2.2	0 / 0	0% / 0%	No	Evaluated	Full

Monitoring and Methods

Assessment Key Dates

9/8/2015	Biological Monitoring
10/11/2010	Biological Monitoring
1/6/2016	Fixed Monitoring Start Date
12/10/2018	Fixed Monitoring End Date
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
230	Fixed station physical/chemical (conventional plus toxic pollutants)
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