Monona-Harrison Ditch IA 06-LSR-1580

mouth (S21 T81N R45W Harrison Co.) to confluence of Wolf Cr. (aka Haitz Ditch) and West Fork Ditch in S12 T84N R45W Monona Co.

This is a DRAFT assessment

Draft assessments may change without notice

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 2022 - 2024
Stream/River Water Quality Data	CY 2022 - 2024
Lake Water Quality Data	CY 2020 - 2024
Biological Sampling Data	CY 2020 - 2024*
Fish Kill Data	CY 2020 - 2024
Fish Tissue Sampling Data	CY 2020 - 2024
Continuous Dissolved Oxygen Sampling Data	CY 2020 - 2024
*Biological sites sampled in both 2019 and 2023 were also assessed.

Open Segment Map
View 2026 assessment summary page

Cycle: 2026
Current Phase: Public Comment
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Declining
Trend Comment: New presumptive Class A1 indicator bacteria impairment and new Class BWW1 selenium impairment.
Created: 10/27/2025 3:10:08 PM
Updated: 1/14/2026 8:10:24 AM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

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

Moderate

Status

New

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2026

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier III

Class BWW1

Aquatic Life - Warm Water Type 1

Not Supported

Biological: low fish IBI

Support Level

Further Investigation Needed

Impairment Code

3b-u - Use potentially biologically impaired based on uncalibrated IBI metrics.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2008

Impairment Rationale

Potential Impairment

Data Source

Biological monitoring: Iowa DNR WQMA

Metals: Selenium

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Moderate

Status

New

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2026

Impairment Rationale

Violations of chronic criterion

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier IV

Class HH

Human Health -

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 violations of the state water quality criteria for indicator bacteria (E. coli). The Class BWW1 use was assessed as "not supported" due to violations of the state selenium chronic criterion and assessed as “WINOFI” based on biological sampling data. The Class HH (fish consumption) 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 2024	10670001	Monona-Harrison Ditch near Turin
Iowa DNR	6	BIO	See Below	912	Monona-Harrison Ditch	Blencoe – REMAP #208

Presumptive Class A1 - Indicator Bacteria:

Site ID	Data Source ID	# Samples per Year (2024)	2024 Geometric Mean	Violates Annual Geometric Mean?	# 2024 SSM violations / SSM Violations needed for impairment	Violates Annual SSM Significantly >10% Rule?	Assessment Type	Support Level
10670001	6	7	218	YES	3 / 3	YES	MONITORED	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
10670001	6	8 / 1	7.8	8.2	8	0	3	NO	MONITORED	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
10670001	6	Chloride	8 / 1	16	26	21	NA	0 / 0	3	NO	EVALUATED	FULL
10670001	6	Dissolved Oxygen	8 / 1	6.1	13.9	8.8	0	NA / NA	3	NO	MONITORED	FULL
10670001	6	pH	8 / 1	7.8	8.2	8	0	NA / NA	3	NO	MONITORED	FULL
10670001	6	Sulfate	8 / 1	37	72	63	0	NA / NA	3	NO	MONITORED	FULL
10670001	6	Temperature	8 / 1	0.8	23.8	16.4	0	NA / NA	3	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
10670001	6	Ammonia	8 / 1	0.17	0.08	0.08	0 / 0	NO	EVALUATED	FULL
10670001	6	Copper	8 / 1	9.7	3.2	2.2	0 / 0	NO	EVALUATED	FULL
10670001	6	Selenium	8 / 1	9.1	7.3	7.6	0 / 7	YES	MONITORED	NOT

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	BM Sample Gear	BMIBI score	BMIBI Class	47d BMIBI BIT	BMIBI Pass/Fail
912	7/19/06	912	47d	MO/WW	ArtSub	52	Fair	54	Pass*

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	Riffle Stream?	FIBI score	FIBI Class	47d FIBI BIT	FIBI Pass/Fail
912	7/19/06	912	47d	MO/WW	NA	14	Poor	31	Fail

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Pass (1/1)	Full		*BMIBI scored passed when 8 point UAV was applied to single sample.
Fish	Evaluated	Fail (0/1)	WINOFI		Assessment was evaluated because the drainage area
Overall	Evaluated	Fail	WINOFI	3bu	of the sample site was larger 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
10670001	6	Copper	8 / 1	9.7	3.2	2.2	1	NO	EVALUATED	FULL
10670001	6	Selenium	8 / 1	9.1	7.3	7.6	0	NO	EVALUATED	FULL

Monitoring and Methods

Assessment Key Dates

7/19/2006

Biological Monitoring

5/14/2024

Monitoring Start

12/4/2024

Monitoring End

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