Iowa River IA 02-IOW-628

from Burlington St. dam in Iowa City (Johnson Co.) to Coralville Reservoir dam (Johnson 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: 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Trend: Unknown

Created: 6/4/2020 9:02:17 AM
Updated: 10/9/2020 8:39:36 AM

Assessment conducted in accordance with Iowa's 2020 IR methodology

Use Support

Class A1

Recreation

Primary contact

Partially Supported

Impairments

Support Level

Partially 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

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Corps of Engineers/ISU/UI

Class BWW1

Aquatic Life

Warm Water Type 1

WINOFI

Further Investigation Needed

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

2008

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

Class C

Drinking Water

Fully Supported

Class HH

Human Health

Fully Supported

General Use

General Use water

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 primary contact recreation use was assessed as "partially supported" based on 2016-2017 ambient monitoring for indicator bacteria. This impairment is covered by the TMDL for bacteria approved by EPA in 2007. The Class BWW1 aquatic life use remains assessed as "partially supported" based on 2013 and 2014 biological sampling data. The Class C (drinking water) use was assessed as "fully supported" based on 2016-2018 ambient water quality monitoring data. The Class HH (fish consumption) use remains assessed as "fully supported" based on 2015 fish tissue sampling data. All other designated uses were "not assessed". Note: A TMDL for indicator bacteria in this segment of Iowa River approved by EPA in June 2007. The approval of this TMDL moves the bacterial impairment for this segment from Iowa's list of Section 303(d) waters (Category 5a) to Category 4a (impaired; TMDL not required). Additionally, 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.

Assessment Explanation

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
USACE	12	WQ	CY 2016-2018	2222222	Iowa River (Downstream Coralville Reservoir)
Iowa DNR	6	FT	See Below	126	Iowa River at Iowa City
Iowa DNR	6	BIO	See Below	941	Iowa River	Iowa City – US1

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
2222222	12	23 / 2	92.53	158.42	NA	Yes	6	26%	Yes	Monitored	Partial

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
2222222	12	65 / 3	8.85	8.14	8.19	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
2222222	12	Ammonia	60 / 3	1.06	0.11	0.06	0 / 0	0% / 0%	No	Monitored	Full
2222222	12	Dissolved oxygen	65 / 3	17.3	10.3	9.1	NA / 0	NA / 0%	No	Monitored	Full
2222222	12	pH	65 / 3	8.85	8.14	8.19	0 / NA	0% / NA	No	Monitored	Full
2222222	12	Temperature	65 / 3	28.9	16.7	20.4	0 / 0	0% / 0%	No	Monitored	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
941	10/10/14	3158	47f	MS/WW	Float ArtSub	38	Fair	51	Fail
941	9/19/13	3158	47f	MS/WW	ArtSub	20	Poor	51	Fail

Overall Assessment:

Community	Assessment Type	Assessment Result	Support Level	Earned IR Category	Actual IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (0/2)	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 calibrated range.

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
2222222	12	Inorganic nitrogen (nitrate and nitrite)	60 / 3	14.3	6.14	6.6	3	5%	No	Monitored	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

126

8/5/2015

white bass

plug

0.050

Monitored

Full

126

8/5/2015

common carp

fillet

<0.02

<0.06

0.09

Monitored

Full

Monitoring and Methods

Assessment Key Dates

1/4/2016

Fixed Monitoring Start Date

12/3/2018

Fixed Monitoring End Date

9/19/2013

Biological Monitoring

10/10/2014

Biological Monitoring

8/15/2015

Fish Tissue Monitoring

6/1/2007

TMDL Completed

3/9/2018

TMDL Completed

Methods

150

Monitoring data more than 5 years old

220

Non-fixed station physical/chemical monitoring (conventional pollutant only)

260

Fish tissue analysis

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

420

Indicator bacteria monitoring