Iowa DNR
ADBNet

Water Quality Assessments

Impaired Waters List

Hickory Grove Lake IA 03-SSK-950

Story County S24T83NR22W 2.5 mi SW of Colo.

Assessment Cycle
2020
Release Status
Final
Release Period
2016 - 2018
Created
7/30/2020 3:50:27 PM
Overall IR Category
5 - Water is impaired or threatened and a TMDL is needed.
Trophic
Eutrophic
Trend
Declining
Trend Comment
Chlorophyll a TSI went from 62 in 2014 to 65 in 2016, resulting in an impairment for "Algal Growth: Chlorophyll a" at Hickory Grove Lake in 2016. Additionally, the Secchi TSI went from 61 (2014) to 65 (2018).
Last Updated
11/23/2020 3:40:07 PM
Assessments conducted in accordance with Iowa's Integrated Report methodology.
Use Support
Class A1
Recreation
Primary contact
Partially Supported
Bacteria: Indicator Bacteria- E. coli
Impairment Code
5a - Pollutant-caused impairment. TMDL needed.
Cause Magnitude
Moderate
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
Cycle Added
2008
Impairment Rationale
Geometric mean criterion exceeded
Data Source
Beach monitoring: Iowa DNR city/county
TMDL Priority
Tier II
Partially Supported
Algal Growth: Chlorophyll a
Impairment Code
5a - Pollutant-caused impairment. TMDL needed.
Cause Magnitude
Slight
Status
Continuing
Source
Agriculture
Source Confidence
Low
Cycle Added
2016
Impairment Rationale
Narrative criteria violation: aesthetically objectionable conditions
Data Source
Ambient monitoring: Iowa DNR-lakes
TMDL Priority
Tier II
Class BLW
Aquatic Life
Lakes and wetlands
Fully Supported
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 use is assessed (monitored) as “partially supported” due to levels of indicator bacteria that exceed Iowa’s water quality standard and aesthetically objectionable conditions caused by algae blooms. The Class BLW use is assessed (monitored) as “fully supported.” Class HH use is assessed as "fully supported" based on fish tissue monitoring.

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 2016-2016

21850001

Hickory Grove Park Beach

Iowa DNR

6

WQ

CY 2014-2018

22850001

Hickory Grove Lake (maximum water depth)

Iowa DNR

FT

See Below

302

Hickory Grove Lake


Class A1 - Indicator Bacteria: data is limited due to US EPA 8-hour holding time enforcement. See historical impairment in previous assessments.

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

21850001

6

3 / 1

27.14

NA

NA

No

1

33%

YES

Evaluated

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

22850001

6

15 / 5

8.7

8.2

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

22850001

6

Chlorophyll a TSI

15 / 5

36

70

60

NO

Monitored

Full

22850001

6

Secchi TSI

15 / 5

40

70

65

YES

Monitored

Not

22850001

6

Total Phosphorus TSI

15 / 5

44

85

62

NA

NA

NA

22850001

6

Inorganic suspended solids

15 / 5

0.6

10

2.9

NA

NA

NA

  • Although the index value for Chlorophyll a is below the impairment trigger of 65 for this assessment cycle, Hickory Grove Lake was listed as partially supporting its Class A1 uses 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 5). Therefore, Hickory Grove Lake will remain listed as "not supported" for the 2020 assessment/listing cycle.

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

22850001

6

Ammonia

15 / 5

0.135

0.04

0.02

0 / 0

0% / 0%

NO

Monitored

Full

22850001

6

Dissolved oxygen

15 / 5

12.7

9.2

9.5

NA / 2

NA / 13%

NO

Monitored

Full

22850001

6

pH

15 / 5

8.7

8.2

8.3

0 / NA

0% / NA

NO

Monitored

Full

22850001

6

Temperature

15 / 5

28

23

23.85

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

22850001

6

11

156.519

95.8 %

10.452

52.8 %

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

302

8/2/13

channel catfish

fillet

5

<0.2

No

<0.6

No

0.09

No

Evaluated

Full

302

9/16/13

largemouth bass

plug

5

0.239

No

Evaluated

Full



Monitoring and Methods
Assessment Key Dates
6/23/2014 Fixed Monitoring Start Date
9/11/2018 Fixed Monitoring End Date
8/2/2013 Fish Tissue Monitoring
9/16/2013 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 Water column surveys (e.g. fecal coliform)