2020 Final assessment for Raccoon River

Raccoon River IA 04-RAC-1116

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

Assessment Cycle

2020

Release Status

Final

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 2016 - 2018
Stream/River Water Quality Data	CY 2016 - 2018
Lake Water Quality Data	CY 2014 - 2018
Biological Sampling Data	CY 2014 - 2018*
Fish Kill Data	CY 2014 - 2018
Fish Tissue Sampling Data	CY 2014 - 2018
Continuous Dissolved Oxygen Sampling Data	CY 2014 - 2018
*Biological sites sampled in both 2013 and 2017 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: 9/18/2020 2:19:53 PM
Updated: 10/13/2020 6:59:47 AM

Assessment conducted in accordance with Iowa's 2020 IR methodology

Use Support

Class A1

Partially Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Partially 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

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

Moderate

Cycle Added

1998

Impairment Rationale

Significantly > 10% of samples fail to meet criterion

Data Source

Ambient monitoring: municipal water supply

Class HH

Not Assessed

General Use

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed as "partially 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 "not supported" due to levels of nitrate that exceeded state water quality standards and U.S. EPA’s maximum contaminant level (MCL). All other designated uses are “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

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
DMWW	13	WQ	CY 2016-2018	99990003	Raccoon River

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
99990003	13	510 / 3	293.17	200.68	247.95	Yes	249	49%	Yes	Monitored	Partial

Class A1 - pH:

Site ID	Data Source ID	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
99990003	13	759 / 3	8.92	8.29	8.31	0	0%	No	Monitored	Full

Class BWW1 - Conventional 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
99990003	13	Chloride	758 / 3	168.79	22.03	20.99	0 / 0	0% / 0%	No	Monitored	Full
99990003	13	pH	759 / 3	8.92	8.29	8.31	0 / NA	0% / NA	No	Monitored	Full
99990003	13	Sulfate	758 / 3	68.2	29.95	29.6	0 / NA	0% / NA	No	Monitored	Full
99990003	13	Temperature	752 / 3	29.4	12.7	12.8	0 / 0	0% / 0%	No	Monitored	Full

Class C - Conventional 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
99990003	13	Chloride	759 / 3	168.79	22.02	20.99	0	0%	No	Monitored	Full
99990003	13	Inorganic nitrogen (nitrate and nitrite)	759 / 3	14.07	7.078	7.07	173	23%	Yes	Monitored	Partial

Class HH - Fish Tissue Sampling: No Data

Previous fish tissue monitoring that occurred in the adjacent segment has been removed from this assessment.

Monitoring and Methods

Assessment Key Dates

1/4/2016	Fixed Monitoring Start Date
12/31/2018	Fixed Monitoring End Date

Methods

210	Fixed station physical/chemical monitoring (conventional pollutants only)
270	PWS chemical monitoring (ambient water)
420	Indicator bacteria monitoring

Water Quality Assessments

Impaired Waters List

Raccoon River IA 04-RAC-1116

Assessment Summary

Assessment Explanation

Assessment Key Dates

Methods