Raccoon River IA 04-RAC-1117

from the Polk/Dallas county line to confluence of North Raccoon and South Raccoon rivers in Dallas 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 3:09:54 PM
Updated: 1/13/2026 9:52:44 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

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2002

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Corps of Engineers/ISU/UI

Class BWW1

Aquatic Life - Warm Water Type 1

Fully Supported

Class C

Drinking Water -

Not Supported

Nutrients: Nitrate

Support Level

Not Supported

Impairment Code

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

Cause Magnitude

High

Status

Continuing

Source

Agriculture

Source Confidence

N/A

Cycle Added

1998

Impairment Rationale

Significantly > 10% of samples fail to meet criterion

Data Source

Ambient monitoring: municipal water supply

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" based on levels indicator bacteria (E. coli) that exceeded state water quality criteria. The Class BWW1 use was assessed as "fully supported" based on water quality monitoring data. The Class C (drinking water) use was assessed as "not supported" due to levels of nitrate that exceeded state water quality standards. The class HH use is "fully supported" based on water quality monitoring data. Note: A TMDL for nitrate and pathogen indicators (E. coli) was prepared by DNR and approved by EPA in June 2008. Because this TMDL covered the primary Section 303(d) impairments identified for the 2006 assessment/listing cycle, this waterbody was moved from IR Category 5a from the 2006 assessment/listing cycle to IR Category 4a (impaired; TMDL approved) for the 2008 cycle. This river segment 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
USACE	12	WQ	CY 2016-2017	17250001	Raccoon River at R16

Class A1 - Indicator Bacteria:

Site ID	Data Source ID	# Samples / # Years	2016 Geometric Mean	2017 Geometric Mean	2018 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
17250001	12	23 / 2	261.32	275.54	NA	Yes	13	57%	Yes	Evaluated	Not

Class A - pH:

Site ID	Data Source ID	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
17250001	12	39 / 2	8.745	8.31	8.31	0	0%	No	Evaluated	Full

Class BWW1 - Binomial Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	% Acute/ Chronic Violations	Significantly >10% Violations	Assessment Type	Support Level
17250001	12	Ammonia	39 / 2	0.28	0.04	0.02	0 / 0	0% / 0%	No	Evaluated	Full
17250001	12	Chloride	3 / 2	25	21	20	0 / 0	0% / 0%	No	Evaluated	Full
17250001	12	Dissolved oxygen	39 / 2	13.3	10.2	10.2	NA / 0	NA / 0%	No	Evaluated	Full
17250001	12	pH	39 / 2	8.745	8.31	8.31	0 / NA	0% / NA	No	Evaluated	Full
17250001	12	Sulfate	4 / 2	33	30	30	0 / NA	0% / NA	No	Evaluated	Full
17250001	12	Temperature	39 / 2	30.2	17.8	21	0 / 0	0% / 0%	No	Evaluated	Full

Class BWW1 - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	% Acute/ Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
17250001	12	Cadmium	3 / 1	0.15	0.15	0.15	0 / 0	0% / 0%	No	Evaluated	Full
17250001	12	Copper	7 / 2	3.9	1.2	1	0 / 0	0% / 0%	No	Evaluated	Full
17250001	12	Lead	3 / 1	0.5	0.5	0.5	0 / 0	0% / 0%	No	Evaluated	Full
17250001	12	Mercury	3 / 1	0.025	0.0175	0.025	0 / 0	0% / 0%	No	Evaluated	Full

Class C - Binomial Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
17250001	12	Inorganic nitrogen (nitrate and nitrite)	39 / 2	15.6	8.79	9.2	16	41%	Yes	Evaluated	Not

Class C - 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
17250001	12	Cadmium	3 / 1	0.15	0.15	0.15	3	No	All Non-Detect	Full
17250001	12	Lead	3 / 1	0.5	0.5	0.5	3	No	All Non-Detect	Full

Class HH-FW - 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
17250001	12	Copper	7 / 2	3.9	1.2	1	3	No	Evaluated	Full
17250001	12	Mercury	3 / 1	0.025	0.0175	0.025	3	No	All Non-Detect	Full

Monitoring and Methods

Assessment Key Dates

1/4/2016

Monitoring Start

8/20/2017

Monitoring End

6/30/2008

TMDL Completed

Methods

150

Monitoring data more than 5 years old

200

Physical/Chemical Monitoring

420

Indicator bacteria monitoring

860

Other Agencies/Organizations provided monitoring data