Iowa DNR
ADBNet

Water Quality Assessments

Impaired Waters List

Frog Hollow (aka Volga Lake) IA 01-VOL-292

Fayette County S3T93NR8W 4 mi. NNE of Fayette.

Assessment Cycle
2022
Release Status
Final
Data Collection Period
Overall IR Category
4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Trophic
Eutrophic
Trend
Stable
Created
12/17/2021 9:55:20 AM
Updated
2/17/2022 8:40:00 AM
Assessment conducted in accordance with Iowa's 2022 IR methodology
Use Support
Class A1
Not Supported
Algal Growth: Chlorophyll a
Support Level
Not Supported
Impairment Code
4a - Pollutant-caused impairment. TMDL has been completed.
Cause Magnitude
Moderate
Status
Continuing
Source
Agriculture
Source Confidence
Moderate
Cycle Added
2006
Impairment Rationale
Narrative criteria violation: aesthetically objectionable conditions
Data Source
Ambient monitoring: Iowa DNR-lakes
Turbidity
Support Level
Not Supported
Impairment Code
4a - Pollutant-caused impairment. TMDL has been completed.
Cause Magnitude
Slight
Status
Continuing
Source
Agriculture
Source Confidence
Moderate
Cycle Added
2010
Impairment Rationale
Narrative criteria violation: aesthetically objectionable conditions
Data Source
Ambient monitoring: Iowa DNR-lakes
Class BLW
WINOFI
Turbidity: Siltation/Turbidity
Support Level
Water in Need of Further Investigation (WINOFI)
Impairment Code
3b - Use potentially impaired based on an evaluated assessment.
Cause Magnitude
Slight
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
Moderate
Cycle Added
2016
Impairment Rationale
Potential Impairment
Data Source
Biological monitoring: Iowa DNR Fisheries
Class HH
Fully Supported
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The Class A1 use was assessed as “not supported” (IR 4a) due to algae blooms and high levels of turbidity that violated Iowa’s narrative criteria protecting against aesthetically objectionable conditions. The Class BLW use was assessed (evaluated) as “WINOFI” based on information from the DNR Fisheries Bureau. The Class HH (fish consumption) use was assessed as "fully supported" based on fish tissue monitoring data. Note: A TMDL for impairments due to algae and non-algal turbidity at this lake was prepared and approved by EPA in July 2014. The approval of this TMDL moves the impairments due to algae and non-algal turbidity from Iowa's list of Section 303(d) waters (Category 5a of the Integrated Report) to IR Category 4a (impaired; TMDL not required).

Assessment Explanation

Data Sources:

Data Source

Data Source ID

Data Type

Data Age

Site ID

Site Name

Site Description

Iowa DNR

6

WQ

CY 2016-2019

22330001

Volga Lake (maximum water depth)

Iowa DNR

6

FT

See Below

271

Volga Lake (Frog Hollow Lake)

Near Fayette


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

22330001

6

12 / 4

7.7

9

8.3

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

22330001

6

Chlorophyll a TSI

12 / 4

42

76

64

NO

Monitored

Full

22330001

6

Secchi TSI

12 / 4

55

83

76

YES

Monitored

Not

22330001

6

Total Phosphorus TSI

12 / 4

37

76

70

NA

NA

NA

22330001

6

Fixed suspended solids

12 / 4

0.3

31.1

3.4

NA

NA

NA

Although the index value for Chlorophyll a is below the impairment trigger of 65 for this assessment cycle, the Class A1 use of Frog Hollow/Volga Lake was listed as "not supported" due to aesthetically objectionable conditions. Based on DNR's methodology, the median TSI value for Chlorophyll a 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 4a). Therefore, Volga will remain listed as "not supported" for the 2022 assessment/listing cycle.


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

22330001

6

Ammonia

12 / 4

0.003

0.349

0.1

NA

0 / 0

4

NO

Monitored

Full

22330001

6

Dissolved Oxygen

12 / 4

5.5

13.1

8.9

0

NA / NA

4

NO

Monitored

Full

22330001

6

pH

12 / 4

7.7

9

8.3

0

NA / NA

4

NO

Monitored

Full

22330001

6

Temperature

12 / 4

18.9

26.5

23

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

22330001

6

6

29.76

91.9%

11.12

67.9%

NO

Evaluated

NA


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)

271

tissue plug

2019

largemouth bass

10

32

0.076

Support Level

Full

Monitoring and Methods
Assessment Key Dates
6/5/2012 TMDL Completed
9/24/2019 Non-fixed Monitoring End Date
6/7/2016 Non-fixed Monitoring Start Date
7/1/2019 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)