2024 Pending assessment for Raccoon River

Raccoon River IA 04-RAC-1116

mouth (at Des Moines Polk Co.) to the Polk/Dallas county line

Assessment Cycle

2024

Release Status

Pending

Data Collection Period

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 2020 - 2022
Stream/River Water Quality Data	CY 2020 - 2022
Lake Water Quality Data	CY 2018 - 2022
Biological Sampling Data	CY 2018 - 2022*
Fish Kill Data	CY 2018 - 2022
Fish Tissue Sampling Data	CY 2018 - 2022
Continuous Dissolved Oxygen Sampling Data	CY 2018 - 2022
*Biological sites sampled in both 2017 and 2021 were also assessed.

Overall IR Category: 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Trend: Unknown

Created: 11/1/2023 8:13:15 AM
Updated: 1/25/2024 7:51:46 AM

Assessment conducted in accordance with Iowa's 2024 IR methodology.

Use Support

Class A1

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

Fully Supported

Class C

Fully Supported

Class HH

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed as "not supported" based on results of monitoring for indicator bacteria (E. coli). The Class BWW1 use was assessed as "fully supported" based on results of ambient chemical/physical water quality monitoring. The Class C use was assessed as "fully supported" based on water quality monitoring data and drinking water compliance monitoring required by the DNR. All other designated uses were “not assessed.” Note: A TMDL for nitrate and pathogen indicators (E. coli) was prepared by DNR and approved by EPA in June 2008. Because this TMDL covers the primary Section 303(d) impairments identified for this IR cycle, this waterbody was moved from IR Category 5a to IR Category 4a (impaired; TMDL approved).

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
DMWW	13	WQ	CY 2020-2022	99990003	Raccoon River

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

99990003

170/171/170

104

101

47 / 23

43 / 23

45 / 23

YES

Mon

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
99990003	13	755 / 3	7.46	8.99	8.27	0	87	NO	Mon	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
99990003	13	Chloride	755 / 3	11.05	288.47	33.13	NA	0 / 0	87	NO	Mon	Full
99990003	13	pH	755 / 3	7.46	8.99	8.27	0	NA / NA	87	NO	Mon	Full
99990003	13	Sulfate	755 / 3	16	67.56	42.2	0	NA / NA	87	NO	Mon	Full
99990003	13	Temperature	755 / 3	-0.55556	29.4444	12.523	0	NA / NA	87	NO	Mon	Full

Class C - Binomial Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	Median Value	# Violations	Violates Significantly >10% Rule?	Assessment Type	Support Level
99990003	13	Chloride	755 / 3	11.05	288.47	33.13	31.73	1	NO	Mon	Full
99990003	13	Fluoride	755 / 3	60	450	276	270	0	NO	Mon	Full
99990003	13	Nitrate	755 / 3	0.02	16.55	3.35	2.31	38	NO	Mon	Full
99990003	13	pH	755 / 3	7.46	8.99	8.27	8.29	0	NO	Mon	Full

Class C - Iowa Drinking Water Compliance Report:

Compliance monitoring required by the Iowa DNR Water Supply Operations and Engineering Sections did not show violations of finished water caused by source water at the Des Moines Water Works facility during the 2020-22 monitoring period. The results of compliance monitoring as reported in annual compliance reports are available at the following location at the Iowa DNR’s home page: https://www.iowadnr.gov/Environmental-Protection/Water-Quality/Water-Supply-Engineering/Annual-Compliance-Report.

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

1/2/2020	Monitoring Start
12/30/2022	Monitoring End

Methods

200	Physical/Chemical Monitoring
275	Drinking water compliance reports
420	Indicator bacteria monitoring
860	Other Agencies/Organizations provided monitoring data

Water Quality Assessments

Impaired Waters List

Raccoon River IA 04-RAC-1116

Assessment Summary

Assessment Explanation

Assessment Key Dates

Methods