Rodgers Park Lake IA 02-CED-526

Benton County S1T86NR11W 3.5 mi NW of Vinton.

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: 5 - Water is impaired or threatened and a TMDL is needed.
Trophic: Eutrophic
Trend: Unknown
Created: 7/17/2020 1:53:23 PM
Updated: 10/14/2020 8:38:21 AM

Use Support

Class A1

Recreation - Primary contact

Fully Supported

Class BLW

Aquatic Life - Lakes and wetlands

Not Supported

Organic Enrichment: Low Dissolved Oxygen

Support Level

Not Supported

Impairment Code

5* - 303(d)-impaired last cycle; fully supporting this cycle; potential de-listing.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2018

Impairment Rationale

Significantly > 10% of samples fail to meet criterion

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier IV

Class HH

Human Health -

Not Assessed

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use is assessed (monitored) as “fully supported.” The Class BLW use is assessed (monitored) as “not supported” due to violations of the criterion for Dissolved Oxygen. Fish consumption uses remain “not assessed.” All other designated uses are “not assessed”.

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	14000236	Rodgers Park Lake Beach
Iowa DNR	6	WQ	CY 2014-2018	22060002	Rodgers Lake

Class A1 - Indicator Bacteria:

Site ID	Data Source ID	# Samples / # Years	2016 Geometric Mean	2017 Geometric Mean	2018 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
14000236	6	1 / 1	NA	NA	10.0	NO	0	0%	NO	Evaluated	Full

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
22060002	6	15 / 5	8.9	8.3	8.3	0	0%	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
22060002	6	Chlorophyll a TSI	15 / 5	36	80	64	NO	Monitored	Full
22060002	6	Secchi TSI	14 / 5	41	77	54	NO	Monitored	Full
22060002	6	Total Phosphorus TSI	15 / 5	46	92	67	NA	NA	NA
22060002	6	Inorganic suspended solids	15 / 5	0.4	7	1.1	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
22060002	6	Ammonia	15 / 5	0.412	0.1	0.08	0 / 0	0% / 0%	NO	Monitored	Full
22060002	6	Dissolved oxygen	15 / 5	14.8	9.8	11.2	NA / 2	NA / 13%	NO	Monitored	Full
22060002	6	pH	15 / 5	8.9	8.3	8.3	0 / NA	0% / NA	NO	Monitored	Full
22060002	6	Temperature	15 / 5	27.6	24.2	23.8	0 / 0	0% / 0%	NO	Monitored	Full

According to DNR's methodology, a lake must meet water quality standards for two consecutive cycles to suggest de-listing. Therefore, Rodgers Lake will remain listed for the 2020 cycle as "not supported" its Class BLW uses due to dissolved oxygen.

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
22060002	6	10	219.385	87.8 %	1.417	8.95 %	NO	Evaluated	NA

Class HH - Toxic Parameters: No Data

Monitoring and Methods

Assessment Key Dates

6/10/2014

Fixed Monitoring Start Date

9/16/2018

Fixed Monitoring End Date

Methods

120

Surveys of fish and game biologists/other professionals

222

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

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)

420

Indicator bacteria monitoring