Nine Eagles Lake IA 05-GRA-1361

Decatur County S18T67NR25W 3.5 mi. SE of Davis City.

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 2020 - 2022
Stream/River Water Quality Data	CY 2020 - 2022
Lake Water Quality Data	CY 2018 - 2022
Biological Sampling Data	CY 2018 - 2022*
Fish Kill Data	CY 2018 - 2022
Fish Tissue Sampling Data	CY 2018 - 2022
Continuous Dissolved Oxygen Sampling Data	CY 2018 - 2022
*Biological sites sampled in both 2017 and 2021 were also assessed.

Open Segment Map
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Cycle: 2024
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trophic: Mesotrophic
Trend: Stable
Created: 11/1/2023 8:13:20 AM
Updated: 2/5/2024 11:03:52 AM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

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

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2006

Impairment Rationale

Geometric mean criterion exceeded

Data Source

TMDL monitoring: Iowa DNR

Class BLW

Aquatic Life - Lakes and wetlands

Fully Supported

Class C

Drinking Water -

Fully Supported

Class HH

Human Health -

Not Supported

Fish Consumption Advisory: Mercury

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

High

Status

Continuing

Source

Agriculture

Source Confidence

N/A

Cycle Added

2006

Impairment Rationale

Fish consumption advisory in effect: no more than 1 meal/week

Data Source

Fish contaminant monitoring: Iowa DNR

TMDL Priority

Tier IV

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed (monitored) as “not supported” due to levels of indicator bacteria that exceeded state water quality standards. 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 remains assessed (monitored) as “not supported” (IR 5a) based on fish tissue sampling data and due to the existence of a one meal/week mercury consumption advisory for largemouth bass on this segment. Note: A TMDL for indicator bacteria E. coli at Nine Eagles Lake was prepared by DNR and approved by EPA in June 2020. Additionally, a TMDL for turbidity at Nine Eagles Lake was prepared by DNR and approved by EPA in 2001. Because the section 303(d) impairments due to mercury in fish tissue at Nine Eagles Lake were not addressed in the TMDL's, this waterbody remains in Category 5a (impaired; TMDL required) for the current assessment cycle.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2020-2022	21270001	Nine Eagles Beach
Iowa DNR	6	WQ	CY 2018-2022	22270002	Nine Eagles Lake
Iowa DNR	6	FT	See Below	1193	Nine Eagles Lake	Near Davis City

Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2020/ 2021/2022)

2020 Geometric Mean

2021 Geometric Mean

2022 Geometric Mean

Violates Annual Geometric Mean?

# 2020 SSM violations / SSM Violations needed for impairment

# 2021 SSM violations / SSM Violations needed for impairment

# 2022 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

21270001

16/15/14

126

122

112

YES

5 / 4

4 / 4

3 / 4

YES

Mon

Not

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
22270002	6	12 / 4	7.72	8.63	8.19	0	4	NO	Mon	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
22270002	6	Chlorophyll a TSI	12 / 4	26	54	39	NO	Mon	Full
22270002	6	Secchi TSI	12 / 4	40	76	44	NO	Mon	Full
22270002	6	Total Phosphorus TSI	12 / 4	29	71	37	NA	NA	NA
22270002	6	Inorganic suspended solids	12 / 4	0.6	3	1.7	NA	NA	NA

Class BLW - Binomial 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
22270002	6	Dissolved Oxygen	12 / 4	4.5	9.4	7.5	1	NA / NA	4	NO	Mon	Full
22270002	6	pH	12 / 4	7.72	8.63	8.19	0	NA / NA	4	NO	Mon	Full
22270002	6	Temperature	12 / 4	20.9	27.8	24.9	0	NA / NA	4	NO	Mon	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
22270002	6	4	2.075322694	83%	0.131112035	20%	NO	Evaluated	NA

Class BLW - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
22270002	6	Ammonia	12 / 4	0.0316	0.02	0.02	0 / 0	NO	Mon	Full

Class C - Binomial 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
22270002	6	Inorganic nitrogen (nitrate and nitrite)	11 / 4	0.02	0.29	0.08	0.02	0	NO	Mon	Full
22270002	6	pH	12 / 4	7.72	8.63	8.19	8.26	0	NO	Mon	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)
1193	tissue plug	2015	largemouth bass	5	33.5	0.498
Support Level	Not	A one meal/week mercury consumption advisory for largemouth bass exists on this segment. Based on IR Methodology, the Class HH (fish consumption) use was assessed as “not supported.”

Monitoring and Methods

Assessment Key Dates

5/21/2018

Monitoring Start

1/25/2001

TMDL Completed

9/5/2022

Monitoring End

7/8/2015

Fish Tissue Monitoring

6/11/2020

TMDL Completed

Methods

150

Monitoring data more than 5 years old

200

Physical/Chemical Monitoring

260

Fish tissue analysis

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)

420

Indicator bacteria monitoring