Coralville Reservoir IA 02-IOW-630

Johnson County S22T80NR6W (dam) 3 mi N of Iowa City.

Open Data Collection Period Modal

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 2018 - 2020
Stream/River Water Quality Data	CY 2018 - 2020
Lake Water Quality Data	CY 2016 - 2020
Biological Sampling Data	CY 2016 - 2020*
Fish Kill Data	CY 2016 - 2020
Fish Tissue Sampling Data	CY 2016 - 2020
Continuous Dissolved Oxygen Sampling Data	CY 2016 - 2020
*Biological sites sampled in both 2015 and 2019 were also assessed.

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Cycle: 2022
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trophic: Eutrophic
Trend: Stable
Created: 12/20/2021 9:21:14 AM
Updated: 1/5/2022 10:36:14 AM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Turbidity

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Moderate

Status

Continuing

Source

Other: Sediment Resuspension

Source Confidence

Moderate

Cycle Added

2006

Impairment Rationale

Narrative criteria violation: aesthetically objectionable conditions

Data Source

Ambient monitoring: Corps of Engineers/ISU/UI

TMDL Priority

Tier II

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2020

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Corps of Engineers/ISU/UI

TMDL Priority

Tier II

Class BWW1

Aquatic Life - Warm Water Type 1

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” due to aesthetically objectionable conditions caused by poor water transparency due to inorganic turbidity and due to high levels of indicator bacteria. The Class BWW1 use was assessed as “fully supported” based on water quality monitoring data. The Class HH (fish consumption) use was assessed as "fully supported" based on fist tissue sampling data.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
USACE	12	WQ	CY 2016-2020	3333333	Coralville Reservoir
USACE	12	WQ	CY 2018-2018	99990026	Sandy Beach (Coralville)
USACE	12	WQ	CY 2018-2018	99990027	Sugar Bottom Beach (Coralville)
USACE	12	WQ	CY 2018-2018	99990028	West Overlook Beach (Coralville)
Iowa DNR	6	WQ	CY 2016-2016	22520004	Coralville Reservoir
Iowa DNR	6	FT	See Below	290	Coralville Reservoir	E of North Liberty

Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2018/ 2019/2020)

2018 Geometric Mean

2019 Geometric Mean

2020 Geometric Mean

Violates Annual Geometric Mean?

# 2018 SSM violations / SSM Violations needed for impairment

# 2019 SSM violations / SSM Violations needed for impairment

# 2020 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

3333333

9/10/10

0 / 3

2 / 3

0 / 3

Monitored

FULL

99990026

22/0/0

139

YES

7 / 5

YES

Monitored

NOT

99990027

17/13/13

3 / 4

0 / 4

Monitored

FULL

99990028

18/14/12

2 / 4

1 / 4

0 / 4

Monitored

FULL

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
22520004	6	3 / 1	8	8.2	8.1	0	2	NO	Evaluated	FULL
3333333	12	101 / 5	7.63	8.77	8.17	0	15	NO	Monitored	FULL

Class A1 - Lake TSI's

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Median Value	Median TSI Violation?	Assessment Type	Support Level
22520004	6	Chlorophyll a TSI	3 / 1	44	60	54	NO	Evaluated	FULL
3333333	12	Chlorophyll a TSI	51 / 5	44	81	62	NO	Monitored	FULL
22520004	6	Secchi TSI	3 / 1	67	77	73	YES	Evaluated	NOT
3333333	12	Secchi TSI	82 / 5	58	99	77	YES	Monitored	NOT
22520004	6	Total Phosphorus TSI	3 / 1	82	87	84	NA	NA	NA
3333333	12	Total Phosphorus TSI	90 / 5	53	99	83	NA	NA	NA
22520004	6	Fixed suspended solids	3 / 1	8.1	25.8	14.8	NA	NA	NA

Class BWW1 - Conventional 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
22520004	6	Ammonia	3 / 1	0.001	0.223	0.09	NA	0 / 0	2	NO	Evaluated	FULL
3333333	12	Ammonia	89 / 5	0.02	0.95	0.15	NA	0 / 0	14	NO	Monitored	FULL
22520004	6	Dissolved Oxygen	3 / 1	5.9	8	7.2	0	NA / NA	2	NO	Evaluated	FULL
3333333	12	Dissolved Oxygen	101 / 5	2.6	23.4	9.3	9	NA / NA	15	NO	Monitored	FULL
22520004	6	pH	3 / 1	8	8.2	8.1	0	NA / NA	2	NO	Evaluated	FULL
3333333	12	pH	101 / 5	7.63	8.77	8.17	0	NA / NA	15	NO	Monitored	FULL
22520004	6	Temperature	3 / 1	22.4	27.8	25.8	0	NA / NA	2	NO	Evaluated	FULL
3333333	12	Temperature	101 / 5	0.2	30	16.7	0	NA / NA	15	NO	Monitored	FULL

Class BLW - Lake Planktonic Cyanobacteria:

Site ID	Data Source ID	# Samples	Maximum Cyanobacteria Wet Mass	Maximum Cyanobacteria % Composition	Median Cyanobacteria Wet Mass	Median Cyanobacteria % Composition	Median Cyanobacteria Concentration = 75th Percentile	Assessment Type	Support Level
22520004	6	3	0.05	2.2%	0.02	1.3%	NO	Evaluated	NA

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)
290	tissue plug	2020	crappie spp.	10	27.9	0.087
290	tissue plug	2020	flathead catfish	4	50.3	0.093
290	tissue plug	2019	walleye	2	49.9	0.081
Support Level	Full

Monitoring and Methods

Assessment Key Dates

1/4/2016

Fixed Monitoring Start Date

12/7/2020

Fixed Monitoring End Date

7/1/2020

Fish Tissue Monitoring

7/1/2019

Fish Tissue Monitoring

Methods

120

Surveys of fish and game biologists/other professionals

222

Non-fixed-station monitoring (conventional during key seasons and flows)

230

Fixed station physical/chemical (conventional plus toxic pollutants)

260

Fish tissue analysis

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)

420

Indicator bacteria monitoring