North Raccoon River IA 04-RAC-1132

from confluence with Indian Cr. (S24 T87N R36W Sac Co.) to confluence with Cedar Cr. in S25 T88N R36W Sac 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: 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Trend: Stable
Created: 10/27/2025 3:09:45 PM
Updated: 2/11/2026 10:18:43 AM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

4a - Pollutant-caused impairment. TMDL has been completed.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

Class BWW1

Aquatic Life - Warm Water Type 1

WINOFI

Biological: low aquatic macroinvertebrate IBI

Support Level

Further Investigation Needed

Impairment Code

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

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2024

Impairment Rationale

Potential Impairment

Data Source

Biological monitoring: Iowa DNR WQMA

Class HH

Human Health -

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed as "not supported" due to levels of indicator bacteria (E. coli) that violated state water quality standards. The Class BWW1 use was assessed as "WINOFI" based on biological sampling data. The Class HH (fish consumption) use was assessed as "fully supported" based on fish tissue sampling data and water quality monitoring data. Note: A TMDL for pathogen indicator impairments in the Raccoon River basin was approved by EPA in 2008. Because this TMDL covers the primary Section 303(d) impairment identified for the 2006 IR cycle, this segment was moved from IR Category 5a to IR Category 4a (impaired; TMDL approved) for the 2008 cycle. This waterbody remains in IR Category 4a for the current cycle.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2022-2024	10810001	North Raccoon River near Lake View
Iowa DNR	6	BIO	See Below	222	North Raccoon River	Sac City
Iowa DNR	6	FT	See Below	1082	North Raccoon River	Downstream of Sac City

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

10810001

7/8/8

379

191

226

YES

5 / 3

4 / 3

5 / 3

YES

MONITORED

NOT

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
10810001	6	36 / 3	7.6	8.6	8.2	0	7	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
10810001	6	Chloride	36 / 3	19	96	44	NA	0 / 0	7	NO	MONITORED	FULL
10810001	6	Dissolved Oxygen	36 / 3	7.6	17.2	10.9	0	NA / NA	7	NO	MONITORED	FULL
10810001	6	pH	36 / 3	7.6	8.6	8.2	0	NA / NA	7	NO	MONITORED	FULL
10810001	6	Sulfate	36 / 3	31	200	94	0	NA / NA	7	NO	MONITORED	FULL
10810001	6	Temperature	36 / 3	0	28.9	12.2	0	NA / NA	7	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
10810001	6	Aluminum	18 / 2	470	151	165	0 / 0	NO	MONITORED	FULL
10810001	6	Ammonia	36 / 3	0.95	0.07	0.02	0 / 0	NO	MONITORED	FULL
10810001	6	Cadmium	18 / 2	0.5	0.5	0.5	0 / 0	NO	MONITORED	FULL
10810001	6	Chromium	18 / 2	23	1.98	0.62	1 / 1	NO	MONITORED	FULL
10810001	6	Copper	18 / 2	3	2.1	2	0 / 0	NO	MONITORED	FULL
10810001	6	Lead	18 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10810001	6	Nickel	18 / 2	3.2	2.2	2.2	0 / 0	NO	MONITORED	FULL
10810001	6	Selenium	36 / 3	4	1.9	2	0 / 0	NO	MONITORED	FULL
10810001	6	Silver	18 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10810001	6	Zinc	18 / 2	4.8	1.5	1	0 / 0	NO	MONITORED	FULL

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	47b BMIBI BIT	BMIBI Pass/Fail
222	8/29/22	709.2	47b	MS	Floating Art Sub	56	Good	62	Fail
222	8/20/19	709.2	47b	MS	Floating Art Sub	56	Good	62	Fail

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (0/2)	WINOFI		Assessment was evaluated because the drainage
Overall	Evaluated	Fail	WINOFI	3bu	area of the site is greater than the calibrated range.

Class HH - Fish Tissue Sampling:

Site ID	Biopart	Year	Species	# in sample / # of samples	Avg Length (cm)	(Avg) Hg (ppm)	Chlordane (ppm)	Sum PCBs (ppm)
1082	fillet	2024	common carp	3	55.8	0.15	<0.05	J0.0249
1082	tissue plug	2016	walleye	3	53.6	0.25
Support Level	Full

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
10810001	6	Copper	18 / 2	3	2.1	2	0	NO	MONITORED	FULL
Site ID	Data Source ID	Parameter Name	# Samples per Year (2022/ 2023/2024)	2022 Mean	2023 Mean	2024 Mean	# Non-Detects per Year (2022/ 2023/2024)	Support Level per Year (2022/ 2023/2024)	Assessment Type	Support Level
10810001	6	Selenium	12/12/12	2.125	1.55	2.092	5/5/2	FS/FS/FS	MONITORED	FULL

Monitoring and Methods

Assessment Key Dates

1/12/2022

Monitoring Start

12/2/2024

Monitoring End

8/29/2022

Biological Monitoring

8/25/2016

Fish Tissue Monitoring

8/20/2019

Biological Monitoring

6/24/2008

TMDL Completed

9/26/2024

Fish Tissue Monitoring

Methods

150

Monitoring data more than 5 years old

200

Physical/Chemical Monitoring

260

Fish tissue analysis

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

420

Indicator bacteria monitoring