2020 Final assessment for Iowa River

Iowa River IA 02-IOW-641

from confluence Timber Cr. (S3 T83N R17W Marshall Co.) to confluence with Asher Cr. in S27 T84N R18W Marshall Co.

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: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown

Created: 9/3/2020 8:43:03 AM
Updated: 10/14/2020 12:56:29 PM

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

Slight

Status

Delisted

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2004

Impairment Rationale

Geometric mean criterion exceeded

Cycle Delisted

2020

Delisting Rationale

TMDL preparation and approval

Data Source

Ambient monitoring: Iowa DNR-rivers

Class BWW1

WINOFI

Biological: low aquatic macroinvertebrate IBI

Support Level

Water in Need of Further Investigation (WINOFI)

Impairment Code

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

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2014

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

Class HH

Partially Supported

Fish Consumption Advisory: Mercury

Support Level

Partially Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2014

Impairment Rationale

Fish consumption advisory in effect: no more than 1 meal/week

Data Source

Fish contaminant monitoring: Iowa DNR

TMDL Priority

Tier IV

General Use

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed as "partially supported" due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The Class BWW1 use remains assessed as "partially supported" based on biological sampling data. The Class HH use remains assessed as “partially supported” based on fish tissue sampling data and due to the existence of a one meal per week fish consumption advisory for mercury. Note: A TMDL covering the bacteria impairments for all segments, with the segment code prefix "IA 02-IOW" in the Iowa River Basin, was approved by EPA in 2018. Due to the completion of the TMDL, the IR category for the Class A1 use was changed from 5a (impaired; TMDL needed) to 4a (impaired; TMDL approved). Because not all impairments identified for this segment are covered by the TMDL, this segment remains in Category 5 of Iowa's Integrated Report (impaired; TMDL needed).

Assessment Explanation

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2016-2018	10640002	Iowa River Downstream of Marshalltown (DS1)
Iowa DNR	6	BIO	See Below	921	Iowa River	Marshalltown - DS1
Iowa DNR	6	FT	See Below	3	Iowa River at Marshalltown

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
10640002	6	22 / 3	217.62	148.03	528.72	Yes	9	41%	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
10640002	6	36 / 3	8.6	8.1	8.2	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
10640002	6	Ammonia	36 / 3	0.81	0.07	0.02	0 / 0	0% / 0%	No	Monitored	Full
10640002	6	Chloride	36 / 3	32	20	20	0 / 0	0% / 0%	No	Monitored	Full
10640002	6	Dissolved oxygen	36 / 3	14.5	10.5	10.2	NA / 0	NA / 0%	No	Monitored	Full
10640002	6	pH	36 / 3	8.6	8.1	8.2	0 / NA	0% / NA	No	Monitored	Full
10640002	6	Sulfate	36 / 3	47	24	23	0 / NA	0% / NA	No	Monitored	Full
10640002	6	Temperature	36 / 3	25.6	11.6	12.3	0 / 0	0% / 0%	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	% Acute/ Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
10640002	6	Aluminum	9 / 2	5.2	1.978	1.3	0 / 0	0% / 0%	No	Evaluated	Full
10640002	6	Arsenic	9 / 2	2.4	1.8	1.7	0 / 0	0% / 0%	No	Evaluated	Full
10640002	6	Cadmium	9 / 2	0.025	0.025	0.025	0 / 0	0% / 0%	No	Evaluated	Full
10640002	6	Chromium	9 / 2	1.3	0.89	0.96	0 / 0	0% / 0%	No	Evaluated	Full
10640002	6	Copper	9 / 2	3.7	1.3	1	0 / 0	0% / 0%	No	Evaluated	Full
10640002	6	Lead	9 / 2	0.11	0.068	0.08	0 / 0	0% / 0%	No	Evaluated	Full
10640002	6	Nickel	9 / 2	3.9	2.8	2.6	0 / 0	0% / 0%	No	Evaluated	Full
10640002	6	Selenium	9 / 2	2.2	1.43	1.4	0 / 0	0% / 0%	No	Evaluated	Full
10640002	6	Zinc	9 / 2	3	1.45	1.3	0 / 0	0% / 0%	No	Evaluated	Full

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/ Thermal	BM Sample Gear	BMIBI score	BMIBI Class	47f BMIBI BIT	BMIBI Pass/ Fail
921	8/27/15	1635	47f	MS/WW	Float ArtSub	57	Good	51	Pass
921	9/11/14	1635	47f	MS/WW	ArtSub	36	Fair	51	Fail
921	9/4/13	1635	47f	MS/WW	Float ArtSub	21	Poor	51	Fail

Overall Assessment:

Community	Assessment Type	Assessment Result	Support Level	Earned IR Category	Actual IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (1/3)	Partial	3bu	3bu	Assessment is evaluated because samples used to complete assessment were not collected in the last five years and the drainage area of the site is larger than the calibrated range.

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
10640002	6	Cadmium	9 / 2	0.025	0.025	0.025	9	No	All Non-Detect	Full
10640002	6	Chromium	9 / 2	1.3	0.89	0.96	0	No	Evaluated	Full
10640002	6	Copper	9 / 2	3.7	1.3	1	0	No	Evaluated	Full
10640002	6	Nickel	9 / 2	3.9	2.8	2.6	0	No	Evaluated	Full
10640002	6	Selenium	9 / 2	2.2	1.43	1.4	0	No	Evaluated	Full
10640002	6	Zinc	9 / 2	3	1.45	1.3	0	No	Evaluated	Full

Class HH – Fish Tissue Sampling:

Site ID

Date

Species Name

Biopart

# in sample

chlordane result

chlordane violation (>0.6)?

PCBs result

PCBs violation (>0.2)?

Hg result

Hg violation (>0.3)?

Assessment Type

Support Level

9/14/2011

common carp

fillet

<0.03

<0.09

0.146

Evaluated

Full

9/14/2011

walleye

plug

0.323

Yes

Evaluated

Partial

9/26/2012

walleye

plug

0.308

Yes

Evaluated

Partial

A one meal/week consumption advisory for mercury exists on this segment of the Iowa River – seeIowa Consumption Advisories

According to the Iowa DNR assessment/listing methodology, the existence of a one meal per week consumption advisory indicates that the fish consumption uses should be assessed as “partially supported.”

Monitoring and Methods

Assessment Key Dates

1/7/2016	Fixed Monitoring Start Date
12/5/2018	Fixed Monitoring End Date
9/14/2011	Fish Tissue Monitoring
9/26/2012	Fish Tissue Monitoring
9/4/2013	Biological Monitoring
9/11/2014	Biological Monitoring
8/27/2015	Biological Monitoring
3/9/2018	TMDL Completed

Methods

150	Monitoring data more than 5 years old
230	Fixed station physical/chemical (conventional plus toxic pollutants)
260	Fish tissue analysis
315	Regional reference site approach
320	Benthic macroinvertebrate surveys
420	Indicator bacteria monitoring

Water Quality Assessments

Impaired Waters List

Iowa River IA 02-IOW-641

Assessment Summary

Assessment Explanation

Assessment Key Dates

Methods