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 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.

Open Segment Map
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Cycle: 2020
Release Status: Final
Overall IR: 3 - Insufficient data exist to determine whether any designated uses are met.
Trophic: Unknown
Trend: Unknown
Created: 8/13/2020 1:54:50 PM
Updated: 10/14/2020 11:47:35 AM

Use Support

Class A1

Recreation - Primary contact

Not Assessed

Class BLW

Aquatic Life - Lakes and wetlands

Not Assessed

Class HH

Human Health -

Not Assessed

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

Insufficient water quality information available to assess use support.

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 2018-2018	22770006	Grays Lake	Lake Deep Point
Iowa DNR		FT	See Below	256	Grays Lake

Class A1 - Indicator Bacteria: No Data

The Class A1 assessment of (monitored) "Fully Supporting" based on indicator bacteria data was changed to "Not Assessed" due to the enforcement of the US EPA 8 hour holding time.

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
22770006	6	3 / 1	9.3	8.5	8.3	1	33%	YES	Evaluated	Not

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	3 / 1	59	72	71	NA	NA	NA
22770006	6	Secchi TSI	3 / 1	67	73	70	NA	NA	NA
22770006	6	Total Phosphorus TSI	3 / 1	75	75	75	NA	NA	NA
22770006	6	Inorganic suspended solids	3 / 1	0.6	5	2	NA	NA	NA

Class BLW - 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
22770006	6	Ammonia	3 / 1	0.138	0.08	0.09	0 / 0	0% / 0%	NA	NA	NA
22770006	6	Dissolved oxygen	3 / 1	13.6	8	6	NA / 1	NA / 33%	NA	NA	NA
22770006	6	pH	3 / 1	9.3	8.5	8.3	1 / NA	33% / NA	NA	NA	NA
22770006	6	Temperature	3 / 1	26.9	26.2	26.4	0 / 0	0% / 0%	NA	NA	NA

Class BLW - Fish Kill:

The Class BLWuses that were assessed (evaluated) as "partially supporting"due to a fish kills in 2005 and 2006 have been removed based on the assessment methodology. The 3b impairment is switched to 3a "not assessed" based on the age of the non-pollutant caused fish kill.

Class HH - Fish Tissue Sampling:

Class HH uses are considered “not assessed” (IR 3a) due to the age of the fish tissue sampling data upon which the previous assessment (“fully supported”) was based.

Monitoring and Methods

Assessment Key Dates

6/11/2018

Fixed Monitoring Start Date

9/17/2018

Fixed Monitoring End Date

Methods

140

Incidence of spills and/or fish kills

260

Fish tissue analysis

420

Indicator bacteria monitoring