DRAFT 2026 assessment for Elk Run

Elk Run IA 02-CED-544

mouth (S6 T88N R12W Black Hawk Co.) to confluence with unnamed tributary in S27 T89N R12W Black Hawk 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

2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.

Trend

Stable

Current Phase

Public Comment

Created

10/27/2025 3:09:41 PM by

Updated

1/9/2026 7:50:19 AM by

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

WINOFI

Bacteria: Indicator Bacteria- E. coli

Support Level

Further Investigation Needed

Impairment Code

3b - Use potentially impaired based on an evaluated assessment.

Cause Magnitude

Moderate

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2022

Impairment Rationale

Potential Impairment

Data Source

Watershed project monitoring

Class BWW2

Aquatic Life - Warm Water Type 2

Fully Supported

303(d) Delistings for this Cycle

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 use was assessed as “WINOFI” due to violations of Iowa water quality criteria for indicator bacteria (E. coli). The Class BWW2 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
CRWQ	23	WQ	CY 2022-2024	99990057	Elk Run

Presumptive Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2022/ 2023/2024)

2022 Geometric Mean

2023 Geometric Mean

2024 Geometric Mean

Violates Annual Geometric Mean?

# 2022 SSM violations / SSM Violations needed for impairment

# 2023 SSM violations / SSM Violations needed for impairment

# 2024 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

99990057

5/5/5

488

315

1423

YES

4 / NA

5 / NA

YES

EVALUATED

WINOFI

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
99990057	23	15 / 3	7.65	8.86	8.01	0	4	NO	MONITORED	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
99990057	23	Chloride	15 / 3	21.3	52.8	34.1	NA	0 / 0	4	NO	MONITORED	FULL
99990057	23	Dissolved Oxygen	14 / 3	3.1	16	8	1	NA / NA	4	NO	MONITORED	FULL
99990057	23	pH	15 / 3	7.65	8.86	8.01	0	NA / NA	4	NO	MONITORED	FULL
99990057	23	Sulfate	15 / 3	13.3	51.2	35.1	0	NA / NA	4	NO	MONITORED	FULL
99990057	23	Temperature	15 / 3	4.1	20.9	15.6	0	NA / NA	4	NO	MONITORED	FULL

Monitoring and Methods

Assessment Key Dates

4/19/2022

Monitoring Start

8/20/2024

Monitoring End

Methods

200

Physical/Chemical Monitoring

420

Indicator bacteria monitoring

860

Other Agencies/Organizations provided monitoring data