Grays Lake IA 04-RAC-1118

Polk County S7T78NR24W at Des Moines.

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: 12/28/2021 1:06:19 PM
Updated: 1/20/2022 8:19:51 AM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Turbidity: Secchi Disk Transparency

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

New

Source

Other: Sediment Resuspension

Source Confidence

Low

Cycle Added

2022

Impairment Rationale

Narrative criteria violation: aesthetically objectionable conditions

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier I

Support Level

Further Investigation Needed

Impairment Code

3b - Use potentially impaired based on an evaluated assessment.

Cause Magnitude

Slight

Status

New

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2022

Impairment Rationale

Significantly > 10% of samples fail to meet criterion

Data Source

Ambient monitoring: Iowa DNR-lakes

Class BLW

Aquatic Life - Lakes and wetlands

WINOFI

Support Level

Further Investigation Needed

Impairment Code

3b - Use potentially impaired based on an evaluated assessment.

Cause Magnitude

Slight

Status

New

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2022

Impairment Rationale

Significantly > 10% of samples fail to meet criterion

Data Source

Ambient monitoring: Iowa DNR-lakes

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 use was assessed (monitored) as “not supported” due to aesthetically objectionable conditions caused by non-algal turbidity and (evaluated) as “WINOFI” due to violations of the Class BLW criterion for pH. The Class BLW use was assessed (evaluated) as “WINOFI” due to violations of the Class BLW criterion for pH. The Class HH (fish consumption) use was assessed as "fully supported" based on fish tissue sampling data.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2018-2020	22770006	Grays Lake
Iowa DNR	6	FT	See Below	256	Grays Lake	Des Moines

Class A1 - Indicator Bacteria: No Data

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
22770006	6	9 / 3	7.8	10.2	8.7	4	NA	NA	Evaluated	WINOFI

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
22770006	6	Chlorophyll a TSI	9 / 3	47	72	64	NO	Monitored	Full
22770006	6	Secchi TSI	9 / 3	62	73	67	YES	Monitored	Not
22770006	6	Total Phosphorus TSI	9 / 3	64	75	70	NA	NA	NA
22770006	6	Inorganic suspended solids	9 / 3	0.6	7.6	2	NA	NA	NA

Class BLW - 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

22770006

Ammonia

9 / 3

0.001

0.138

0.04

0 / 0

Evaluated

Full

22770006

Dissolved Oxygen

9 / 3

4.3

18.3

8.3

NA / NA

Evaluated

Full

22770006

9 / 3

7.8

10.2

8.7

NA / NA

Evaluated

WINOFI

22770006

Temperature

9 / 3

28.6

NA / NA

Evaluated

Full

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)
256	tissue plug	2019	bluegill	10	15.7	0.037
256	tissue plug	2020	channel catfish	10	51.2	0.123
256	tissue plug	2019	largemouth bass	10	34.7	0.108
256	tissue plug	2019	white crappie	10	22.7	0.067
Support Level	Full

Monitoring and Methods

Assessment Key Dates

6/11/2018

Fixed Monitoring Start Date

8/24/2020

Fixed Monitoring End Date

7/1/2019

Fish Tissue Monitoring

7/1/2020

Fish Tissue Monitoring

Methods

222

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

260

Fish tissue analysis