Bear Creek IA 03-SSK-959

from north line of S32 T85N R23W (Story Co.) to confluence with unnamed tributary in NE 1/4 S23 T86N R23W Hamilton 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: 3 - Insufficient data exist to determine whether any designated uses are met.
Trend: Unknown
Created: 10/27/2025 3:09:43 PM
Updated: 1/13/2026 7:38:02 AM

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

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2024

Impairment Rationale

Potential Impairment

Data Source

Special project/study

Class BWW1

Presumptive Use

Aquatic Life - Warm Water Type 1

WINOFI

Biological: low fish & invert IBIs- cause unknown

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

2004

Impairment Rationale

Potential Impairment

Data Source

Biological monitoring: Iowa DNR WQMA

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 use was assessed as "WINOFI" based on E. coli monitoring data. The presumptive Class BWW1 use was assessed as "WINOFI" based on biological sampling data.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Prairie Rivers/City of Ames	26	WQ	CY 2020-2022	99990161	Bear Creek
Iowa DNR	6	BIO	See Below	109	Bear Creek	Roland WWTP - DS
Iowa DNR	6	BIO	See Below	110	Bear Creek	Roland WWTP - US
Iowa DNR	6	BIO	See Below	654	Bear Creek	Roland – Mixed HWCRS

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

99990161

7/0/1

234

4494

YES

3 / 3

1 / NA

YES

Evaluated

WINOFI

The bacteria samples were collected by the Prairie Rivers Watershed Group and Story County Conservation with the analyses conducted by the City of Ames. Since the data were not collected under a DNR-approved quality assurance plan, the assessment was considered "evaluated" instead of "monitored." According to Iowa DNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). The Iowa DNR does, however, consider these impairments as appropriate for listing under Category 3b of the Integrated Report (waters potentially impaired and in need of further investigation).

Presumptive Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	BM Sample Gear	BMIBI score	BMIBI Class	47b BMIBI BIT	BMIBI Pass/Fail
109	9/10/03	19	47b	MS/WW	Surber	38	Fair	62	Fail

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	Riffle Stream?	FIBI score	FIBI Class	47b FIBI BIT	FIBI Pass/Fail
654	9/28/07	15	47b	MS/WW	No	35	Fair	32	Pass
109	9/10/03	19	47b	MS/WW	No	20	Poor	32	Fail
110	9/10/03	18	47b	MS/WW	No	26	Fair	32	Fail

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (0/1)	WINOFI
Fish	Evaluated	Fail (1/3)	WINOFI		Assessment was evaluated because it included samples not collected in the last five
Overall	Evaluated	Fail	WINOFI	3bu	years and the drainage areas of the sites were smaller than the calibrated range.

Monitoring and Methods

Assessment Key Dates

9/10/2003

Biological Monitoring

9/28/2007

Biological Monitoring

4/15/2020

Monitoring Start

6/15/2022

Monitoring End

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

860

Other Agencies/Organizations provided monitoring data