Des Moines River IA 04-UDM-1211

from Center Street Dam in Des Moines to the Interstate 80/35 bridge in S17 T79N R24W Polk Co.

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: Stable

Created: 11/1/2023 8:13:15 AM
Updated: 1/25/2024 7:51:54 AM

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

Use Support

Class A1

Recreation

Primary contact

Not Supported

Impairments

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

2010

Impairment Rationale

Single-sample maximum criterion exceeded in significantly > 10% of samples

Data Source

Ambient monitoring: municipal water supply

Class BWW1

Aquatic Life

Warm Water Type 1

Fully Supported

Class C

Drinking Water

Fully Supported

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 of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW1 use was assessed as "fully supported" based on water quality monitoring data. The Class C use was assessed as "fully supported" based on water quality monitoring data and drinking water compliance monitoring required by the DNR. The Class HH use was assessed as "fully supported" based on fish tissue sampling data. A TMDL for bacteria was prepared by DNR and approved by U.S. EPA in March 2010. Because this TMDL covers the bacteria impairment identified for this segment, the Class A1 designated use remain in IR Category 4a (impaired; TMDL approved) for this cycle. Additionally, a TMDL for nitrate was prepared by DNR and approved by EPA in September 2009. However, the 2018-2020 nitrate monitoring data indicated "full support."

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	99990015	Des Moines River
USACE	12	FT	See Below	17770001	Des Moines River at 66th. St.	Site 5

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

99990015

170/170/170

30 / 23

24 / 23

18 / 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
99990015	13	758 / 3	7.74	8.86	8.28	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
99990015	13	Chloride	758 / 3	15.19	94.47	35.97	NA	0 / 0	87	NO	Mon	Full
99990015	13	pH	758 / 3	7.74	8.86	8.28	0	NA / NA	87	NO	Mon	Full
99990015	13	Sulfate	758 / 3	29.76	147.51	81.38	0	NA / NA	87	NO	Mon	Full
99990015	13	Temperature	758 / 3	-1.11111	28.8889	12.649	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
99990015	13	Chloride	758 / 3	15.19	94.47	35.97	35.63	0	NO	Mon	Full
99990015	13	Fluoride	755 / 3	200	560	372	370	0	NO	Mon	Full
99990015	13	Nitrate	758 / 3	0.02	11.31	2.97	1.52	11	NO	Mon	Full
99990015	13	pH	758 / 3	7.74	8.86	8.28	8.27	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 - Fish Tissue Sampling:

Site ID	Biopart	Year	Species	# in sample / # of samples	Avg Length (cm)	(Avg) Hg (ppm)	Chlordane (ppm)	Sum PCBs (ppm)
17770001	whole	2016	common carp	5	NA	NA	0.03	<0.06
17770001	fillet	2016	largemouth bass	2	NA	0.11
Support Level	Full	Monitored

Monitoring and Methods

Assessment Key Dates

1/2/2020

Monitoring Start

12/30/2022

Monitoring End

1/2/2018

Fish Tissue Monitoring

3/1/2010

TMDL Completed

9/1/2009

TMDL Completed

Methods

200

Physical/Chemical Monitoring

260

Fish tissue analysis

275

Drinking water compliance reports

420

Indicator bacteria monitoring

860

Other Agencies/Organizations provided monitoring data