DRAFT 2026 assessment for Waterloo Creek

Waterloo Creek IA 01-UIA-253

mouth (S35 T100N R6W Allamakee Co.) to IA/MN state line (S9 T100N R6W Allamakee Co.)

This is a DRAFT assessment

Draft assessments may change without notice

2026
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

Overall IR

5 - Water is impaired or threatened and a TMDL is needed.

Trend

Stable

Current Phase

Public Comment

Created

10/27/2025 3:09:33 PM by

Updated

1/30/2026 3:39:56 PM by

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

Slight

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Watershed project monitoring

TMDL Priority

Tier III

Class A2

Recreation - Secondary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2012

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Watershed project monitoring

TMDL Priority

Tier III

Class BCW1

Aquatic Life - Cold Water Type 1

Not Supported

Biological: low aquatic macroinvertebrate IBI

Support Level

Not Supported

Impairment Code

5b-v - Biological - verified

Cause Magnitude

Slight

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2022

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

TMDL Priority

Tier IV

Class HH

Human Health -

Not Assessed

303(d) Delistings for this Cycle

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 use and the Class A2 use remain assessed as “not supported” due to levels of indicator bacteria that exceeded state water quality criteria. The Class BCW1 use was assessed as "not 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	BIO	See Below	360	Waterloo Creek	Dorchester – REMAP #63
Iowa DNR	6	BIO	See Below	802	Waterloo Creek	Dorchester
Iowa DNR	6	WQ	CY 2012-2014	190050003	Waterloo Creek	Site 26

Presumptive Class A1 - Indicator Bacteria: 2012-2014

Site ID

Data Source ID

# Samples per Year (2012/ 2013/2014)

2012 Geometric Mean

2013 Geometric Mean

2014 Geometric Mean

Violates Annual Geometric Mean?

# 2012 SSM violations / SSM Violations needed for impairment

# 2013 SSM violations / SSM Violations needed for impairment

# 2014 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

190050003

7/7/7

112

273

237

YES

2 / 3

3 / 3

YES

EVALUATED

NOT

Class A2 - Indicator Bacteria: 2012-2014

Site ID

Data Source ID

# Samples per Year (2012/ 2013/2014)

2012 Geometric Mean

2013 Geometric Mean

2014 Geometric Mean

Violates Annual Geometric Mean?

# 2012 SSM violations / SSM Violations needed for impairment

# 2013 SSM violations / SSM Violations needed for impairment

# 2014 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

190050003

7/7/7

112

273

237

0 / 3

1 / 3

EVALUATED

The Class A2 assessment based on the 2012-2014 indicator bacteria data suggest full support; however, the assessment was inconclusive based on low annual sample numbers (7).

Class HH - No Data

Class BCW1 - Biological Sampling:

Benthic Macroinvertebrates:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	CBI score	CBI Class	CBI BIT	CBI Pass/Fail
802	7/31/24	34.2	52b	MS	Hess	56	NA	60	Fail
360	7/19/23	23.2	52b	MS	Hess	51	NA	60	Fail
802	9/1/20	34.2	52b	MS	Hess	56	NA	60	Fail

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Monitored	Fail (0/3)	Not		Assessment was monitored because the assessment used multiple
Overall	Monitored	Fail	Not	5bv	samples collected in a recent five-year period to complete the assessment.

Aquatic Life Use - Trout Natural Reproduction

Based on the latest trout reproduction in Iowa streams summary prepared by the DNR Fisheries Bureau, the aquatic life use was assessed as "fully supported." According to the summary, a portion, or all, of this assessment unit was placed in Category I: streams that exhibit consistent natural reproduction and maintain a wild population of one or more trout species without any stocking.

Monitoring and Methods

Assessment Key Dates

7/31/2024

Biological Monitoring

4/3/2012

Monitoring Start

10/7/2014

Monitoring End

1/1/2025

Biological Monitoring

9/1/2020

Biological Monitoring

7/19/2023

Biological Monitoring

Methods

150

Monitoring data more than 5 years old

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys

420

Indicator bacteria monitoring