Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Brushy Creek Lake IA 04-UDM-1276

Webster Co. in S34 T88N R27W; 5 miles E. of Lehigh

Cycle
2020
Release Status
Final
Overall IR
5 - Water is impaired or threatened and a TMDL is needed.
Trophic
Eutrophic
Trend
Stable
Created
8/20/2020 8:25:02 AM
Updated
10/14/2020 1:27:18 PM
Use Support
Class A1
Recreation - Primary contact
Partially Supported
Support Level
Partially Supported
Impairment Code
5a - Pollutant-caused impairment. TMDL needed.
Cause Magnitude
Slight
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
Cycle Added
2012
Impairment Rationale
Single-sample maximum criterion exceeded in significantly > 10% of samples
Data Source
Beach monitoring: Iowa DNR WQMA
TMDL Priority
Tier II
Class BLW
Aquatic Life - Lakes and wetlands
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
Adverse impacts on plant/animal communities
Data Source
Biological monitoring: Iowa DNR Fisheries
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 violations of the state's indicator bacteria criteria. The Class BLW uses are assessed (evaluated) as “partially supported” due to invasive species. Class HH uses are assessed as "fully supporting" Based on fish tissue sampling.

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 2016-2018

21940001

Brushy Creek (Brushy Creek Recreation Area)

Iowa DNR

6

WQ

CY 2014-2018

22940002

Brushy Creek Lake

Lake Deep Point

Iowa DNR

FT

See Below

285

Brushy Creek 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

21940001

6

17 / 3

39.96

32.25

530

Yes

2

12%

No

Monitored

Partial

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

22940002

6

15 / 5

8.5

8.1

8.2

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

22940002

6

Chlorophyll a TSI

15 / 5

31

63

50

NO

Monitored

Full

22940002

6

Secchi TSI

15 / 5

34

62

54

NO

Monitored

Full

22940002

6

Total Phosphorus TSI

15 / 5

33

83

55

NA

NA

NA

22940002

6

Inorganic suspended solids

15 / 5

0.4

5.2

1.6

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

22940002

6

Ammonia

15 / 5

0.331

0.1

0.05

0 / 0

0% / 0%

NO

Monitored

Full

22940002

6

Dissolved oxygen

15 / 5

20.2

9.9

10

NA / 1

NA / 7%

NO

Monitored

Full

22940002

6

pH

15 / 5

8.5

8.1

8.2

0 / NA

0% / NA

NO

Monitored

Full

22940002

6

Temperature

15 / 5

27.5

20.28

22.8

0 / 0

0% / 0%

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 Wet Mass = 75th Percentile

Assessment Type

Support Level

22940002

6

11

59.197

86.8 %

1.379

45.7 %

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

285

8/30/16

largemouth bass

plug

5

0.050

No

Monitored

Full

285

8/29/13

largemouth bass

plug

5

0.232

No

Evaluated

Full

285

8/29/13

channel catfish

fillet

3

<0.2

No

<0.6

No

<0.05

No

Evaluated

Full

Additional Information:

The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported” based on information from the DNR Fisheries Bureau and results from the ISU lake surveys. Information from the DNR Fisheries Bureau indicates this lake has excessive growth of curly-leaf pondweed and brittle naiad. Additionally, Zebra mussel veligers were recently discovered in the lake.

Monitoring and Methods
Assessment Key Dates
5/19/2014
Fixed Monitoring Start Date
8/14/2018
Fixed Monitoring End Date
8/29/2013
Fish Tissue Monitoring
8/30/2016
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)
420
Indicator bacteria monitoring