Easter Lake IA 04-LDM-1024

Polk County S19T78R23W SE edge of 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.

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Cycle: 2020
Release Status: Final
Overall IR: 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Trophic: Eutrophic
Trend: Stable
Created: 8/12/2020 10:39:25 AM
Updated: 10/14/2020 10:49:25 AM

Use Support

Class A1

Recreation - Primary contact

Partially Supported

Turbidity

Support Level

Partially Supported

Impairment Code

4a - Pollutant-caused impairment. TMDL has been completed.

Cause Magnitude

Moderate

Status

Continuing

Source

Construction

Source Confidence

Moderate

Cycle Added

1998

Impairment Rationale

Narrative criteria violation: aesthetically objectionable conditions

Data Source

Ambient monitoring: Iowa DNR-lakes

Class BLW

Aquatic Life - Lakes and wetlands

WINOFI

Sedimentation/Siltation

Support Level

Further Investigation Needed

Impairment Code

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

Cause Magnitude

Moderate

Status

Continuing

Source

Construction

Source Confidence

Moderate

Cycle Added

1998

Impairment Rationale

Adverse impacts on plant/animal communities

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 uses are assessed (monitored) as “partially supported” due to poor water transparency that violates Iowa’s narrative criteria protecting against aesthetically objectionable conditions. The Class BLW uses are assessed (evaluated) as “partially supported” due to siltation impacts at this lake. Class HH uses are assessed (monitored) as “fully supported” based on fish tissue monitoring. Note: A TMDL for nutrients and siltation at Easter Lake was prepared by DNR and approved by EPA in 2005. Because all Section 303(d) impairments identified for the current assessment/listing cycle (siltation and turbidity) are addressed by the TMDL, this waterbody is placed in IR Category 4a (impaired; TMDL approved).

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 2014-2015	22770001	Easter Lake (maximum water depth)	Lake deep point
Iowa DNR		FT	See Below	9	Easter Lake

Class A1 - Indicator Bacteria: No Data.

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
22770001	6	6 / 2	8.61	8.41	8.4	0	0%	NO	Evaluated	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
22770001	6	Chlorophyll a TSI	6 / 2	54	68	62	NO	Evaluated	Full
22770001	6	Secchi TSI	6 / 2	59	77	64	NO	Evaluated	Full
22770001	6	Total Phosphorus TSI	6 / 2	57	72	64	NA	NA	NA
22770001	6	Inorganic suspended solids	6 / 2	3	17.5	4.9	NA	NA	NA

Although the index value for Secchi is below the impairment trigger of 65 for this assessment cycle, Easter Lake was listed as partially supporting its Class A1 uses due to aesthetically objectionable conditions. Based on DNR's methodology, the median TSI value for Secchi must be 63 or less for two consecutive assessment/listing cycles before a lake can be removed from the state's Section 303(d) list (IR Category 5). Therefore, Easter Lake will remain listed as "not supported" for the 2020 assessment/listing cycle.

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
22770001	6	Ammonia	6 / 2	0.0624	0.02	0.01	0 / 0	0% / 0%	NO	Evaluated	Full
22770001	6	Dissolved oxygen	6 / 2	11.53	9.76	9.6	NA / 0	NA / 0%	NO	Evaluated	Full
22770001	6	pH	6 / 2	8.61	8.41	8.4	0 / NA	0% / NA	NO	Evaluated	Full
22770001	6	Temperature	6 / 2	27.7	24.2	24.4	0 / 0	0% / 0%	NO	Evaluated	Full

The Class BLW uses are assessed (evaluated) as “partially supported” due to the impacts of siltation at this lake. Information from the DNR Fisheries Bureau also suggests that a poor fishery exists at Easter Lake.

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 Wet Mass = 75th Percentile	Assessment Type	Support Level
22770001	6	6	55.223	72.6 %	8.117	30.6 %	NO	Evaluated	NA

Class HH - Fish Tissue Sampling:

Site ID

Date

Species Name

Biopart

# in sample

chlordane result

chlordane violation?

PCBs result

PCBs violation?

Hg result

Hg violation?

Assessment Type

Support Level

8/26/16

channel catfish

fillet

0.04

<0.06

<0.05

Monitored

Full

7/31/15

channel catfish

fillet

<0.02

0.25

Yes

0.03

Monitored

Partial

8/21/15

largemouth bass

plug

0.089

Monitored

Full

Monitoring and Methods

Assessment Key Dates

5/27/2014

Fixed Monitoring Start Date

8/25/2015

Fixed Monitoring End Date

7/31/2015

Fish Tissue Monitoring

8/26/2016

Fish Tissue Monitoring

8/21/2015

Fish Tissue Monitoring

Methods

120

Surveys of fish and game biologists/other professionals

222

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

260

Fish tissue analysis

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)