Silver Lake IA 06-LSR-1669

Dickinson County S28T100NR38W near Lake Park.

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: 1/4/2022 11:17:27 AM
Updated: 1/6/2022 9:18:48 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

Moderate

Cycle Added

2022

Impairment Rationale

Narrative criteria violation: aesthetically objectionable conditions

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier I

Class BLW

Aquatic Life - Lakes and wetlands

Fully Supported

Class C

Drinking Water -

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 (monitored) as “not supported” due to aesthetically objectionable conditions caused by non-algal turbidity. The Class BLW use was assessed (monitored) as “fully supported.” The Class C use was assessed (monitored) as “fully supported.” The Class HH (fish consumption) use was assessed (monitored) as "fully supported" based on fish tissue sampling data. Note: A TMDL for turbidity at Silver Lake was prepared by DNR and approved by EPA in 2009.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2016-2020	22300007	Silver Lake Max Depth
Iowa DNR	6	FT	See Below	200	Silver Lake	Near Lake Park

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
22300007	6	12 / 4	8.2	8.7	8.4	0	4	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
22300007	6	Chlorophyll a TSI	13 / 5	26	80	54	NO	Monitored	Full
22300007	6	Secchi TSI	13 / 5	50	77	65	YES	Monitored	Not
22300007	6	Total Phosphorus TSI	13 / 5	53	88	74	NA	NA	NA
22300007	6	Inorganic suspended solids	13 / 5	0.3	38	4	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
22300007	6	Ammonia	12 / 4	0.007	0.244	0.1	NA	0 / 0	4	NO	Monitored	Full
22300007	6	Dissolved Oxygen	12 / 4	7.1	10.6	8.7	0	NA / NA	4	NO	Monitored	Full
22300007	6	pH	12 / 4	8.2	8.7	8.4	0	NA / NA	4	NO	Monitored	Full
22300007	6	Temperature	12 / 4	15.9	27.7	22.2	0	NA / NA	4	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
22300007	6	5	11.25	99.0%	2.00	94.8%	NO	Evaluated	NA

Class C - Conventional Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	Median Value	# Violations	Violates Significantly >10% Rule?	Assessment Type	Support Level
22300007	6	Inorganic nitrogen (nitrate and nitrite)	13 / 5	0.02	9	1.79	0.97	0	NO	Monitored	Full
22300007	6	pH	12 / 4	8.2	8.7	8.4	8.4	0	NO	Monitored	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)
200	fillet	2014	channel catfish	5	45.0	0.03	0.1	0.06
200	tissue plug	2019	northern pike	10	66.0	0.116
200	tissue plug	2020	walleye	10	48.8	0.151
Support Level	Full

Monitoring and Methods

Assessment Key Dates

6/1/2016

Fixed Monitoring Start Date

9/21/2020

Fixed Monitoring End Date

7/28/2014

Fish Tissue Monitoring

10/24/2014

Fish Tissue Monitoring

9/9/2009

TMDL Completed

7/1/2019

Fish Tissue Monitoring

7/1/2020

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)