College Creek IA 03-SSK-955

mouth (S 1/2 S3 T83N R24W Story Co.) to headwaters in E 1/2 S11 T83N R25W Boone 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: Stable
Created: 10/27/2025 3:09:42 PM
Updated: 11/24/2025 2:06:55 PM

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 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

2010

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
Story Co.	26	WQ	CY 2022-2024	99990163	College Creek	Site monitored by Prairie River Watershed Group and Story Co. Conservation

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

99990163

4/6/4

2837

1770

2576

YES

4 / NA

6 / NA

4 / 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 assessments 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:

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	Riffle Stream?	FIBI score	FIBI Class	47b FIBI BIT	FIBI Pass/Fail
645	9/24/07	1.5	47b	MS/WW	No	11	Poor	32	Fail
646	9/24/07	1.6	47b	MS/WW	No	20	Poor	32	Fail
647	9/24/07	2.9	47b	MS/WW	No	10	Poor	32	Fail

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Fish	Evaluated	Fail (0/3)	WINOFI		Assessment was evaluated because the drainage areas
Overall	Evaluated	Fail	WINOFI	3bu	of the sites were smaller than the calibrated range.

Monitoring and Methods

Assessment Key Dates

9/24/2007

Biological Monitoring

3/16/2022

Monitoring Start

8/21/2024

Monitoring End

Methods

150

Monitoring data more than 5 years old

315

Regional reference site approach

330

Fish surveys

420

Indicator bacteria monitoring

860

Other Agencies/Organizations provided monitoring data