Big Creek Lake IA 04-UDM-1242

Polk County S22T81NR25W near Polk 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: Eutrophic
Trend: Stable
Created: 11/1/2023 8:13:16 AM
Updated: 2/5/2024 9:38:53 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

Moderate

Cycle Added

2006

Impairment Rationale

Single-sample maximum criterion exceeded in significantly > 10% of samples

Data Source

Beach monitoring: Iowa DNR WQMA

Algal Growth: Chlorophyll a

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

Continuing

Source

Agriculture

Source Confidence

Moderate

Cycle Added

2020

Impairment Rationale

Narrative criteria violation: aesthetically objectionable conditions

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier I

Class BWW1

Aquatic Life - Warm Water Type 1

WINOFI

Fish Kill: Due To Natural Causes

Support Level

Further Investigation Needed

Impairment Code

3b - Use potentially impaired based on an evaluated assessment.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2016

Impairment Rationale

Non Pollutant-caused fish kill

Data Source

Biological monitoring: Iowa DNR Fisheries

Class HH

Human Health -

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed (monitored) as “not supported” due to violations of the state water quality criteria for indicator bacteria and secondarily by the presence of aesthetically objectionable conditions caused by algal blooms. The Class BWW1 use was assessed (evaluated) as “WINOFI” based on the results of a fish kill investigation and information from the DNR Fisheries Bureau. The Class HH (fish consumption) use was assessed (monitored) as “fully supported” based on fish tissue sampling data. Note: The DNR TMDL for the impairment due to indicator bacteria at this lake was approved by U.S. EPA in August 2011. Because this TMDL does not address all of the impairments identified for this lake (Algal Growth: Chlorophyll a), this lake remains in IR Category 5a (impaired; TMDL 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 2020-2022	21770001	Big Creek Beach
Iowa DNR	6	WQ	CY 2018-2022	22770004	Big Creek	Lake Deep Point
Iowa DNR	6	WQ	CY 2018-2022	26770002	Big Creek 319 (BCL4)	TMDL north arm sampling point
Iowa DNR	6	WQ	CY 2018-2022	26770004	Big Creek 319 (BCL5)	TMDL west arm sampling point
Iowa DNR	6	WQ	CY 2021-2022	14000414	Big Creek TMDL 1
Iowa DNR	6	WQ	CY 2021-2022	14000415	Big Creek TMDL 2
Iowa DNR	6	WQ	CY 2021-2022	14000416	Big Creek TMDL 3
Iowa DNR	6	WQ	CY 2018-2019	26770003	Big Creek 319 (BCL3)	TMDL central sampling point
Iowa DNR	6	FT	See Below	1052	Big Creek Lake	NW of Polk 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

21770001

12/15/15

182

YES

2 / 4

1 / 4

6 / 4

YES

Mon

Not

22770004

0/5/5

0 / NA

Eval

Full

26770002

0/5/5

0 / NA

Eval

Full

26770004

0/5/5

0 / NA

Eval

Full

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
14000414	6	20 / 2	7.7	8.6	8.3	0	5	NO	Evaluated	Full
14000415	6	20 / 2	7.9	8.7	8.4	0	5	NO	Evaluated	Full
14000416	6	19 / 2	8	8.8	8.4	0	5	NO	Evaluated	Full
22770004	6	35 / 5	7.5	8.6	8.2	0	7	NO	Mon	Full
26770002	6	19 / 2	8.1	9	8.4	0	5	NO	Evaluated	Full
26770004	6	19 / 2	8.2	9	8.5	0	5	NO	Evaluated	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
22770004	6	Chlorophyll a TSI	48 / 5	26	78	64	NO	Mon	Full
22770004	6	Secchi TSI	35 / 5	37	70	60	NO	Mon	Full
22770004	6	Total Phosphorus TSI	48 / 5	37	85	63	NA	NA	NA
22770004	6	Inorganic suspended solids	15 / 5	0.6	12	2	NA	NA	NA

Although the index value for Chlorophyll a is below the impairment threshold of 65 for this assessment cycle, Big Creek 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 below and a monitored assessment before it can be removed from the state's Section 303(d) list (IR Category 5). Therefore, Big Creek Lake will remain listed as "not supported" for the current assessment/listing cycle.

Class BWW1 - 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
14000414	6	Dissolved Oxygen	20 / 2	5.1	17	9.5	0	NA / NA	5	NO	Evaluated	Full
14000414	6	pH	20 / 2	7.7	8.6	8.3	0	NA / NA	5	NO	Evaluated	Full
14000414	6	Temperature	20 / 2	7.3	28.3	22.6	0	NA / NA	5	NO	Evaluated	Full
14000415	6	Dissolved Oxygen	20 / 2	6.2	18.1	9.8	0	NA / NA	5	NO	Evaluated	Full
14000415	6	pH	20 / 2	7.9	8.7	8.4	0	NA / NA	5	NO	Evaluated	Full
14000415	6	Temperature	20 / 2	7.2	28.5	22.7	0	NA / NA	5	NO	Evaluated	Full
14000416	6	Dissolved Oxygen	19 / 2	6.79	21.08	10.76	0	NA / NA	5	NO	Evaluated	Full
14000416	6	pH	19 / 2	8	8.8	8.4	0	NA / NA	5	NO	Evaluated	Full
14000416	6	Temperature	19 / 2	7.3	28.9	22.9	0	NA / NA	5	NO	Evaluated	Full
21770001	6	Dissolved Oxygen	30 / 2	8.12	23.29	11.79	0	NA / NA	6	NO	Evaluated	Full
21770001	6	pH	30 / 2	8.19	9.04	8.64	1	NA / NA	6	NO	Evaluated	Full
21770001	6	Temperature	30 / 2	17	31	27	0	NA / NA	6	NO	Evaluated	Full
22770004	6	Dissolved Oxygen	34 / 5	2.8	16.2	8	6	NA / NA	7	NO	Mon	Full
22770004	6	pH	35 / 5	7.5	8.6	8.2	0	NA / NA	7	NO	Mon	Full
22770004	6	Temperature	35 / 5	7.3	28.3	22.8	0	NA / NA	7	NO	Mon	Full
26770002	6	Dissolved Oxygen	19 / 2	7.3	15	10.3	0	NA / NA	5	NO	Evaluated	Full
26770002	6	pH	19 / 2	8.1	9	8.4	0	NA / NA	5	NO	Evaluated	Full
26770002	6	Temperature	19 / 2	7	29.8	22.8	0	NA / NA	5	NO	Evaluated	Full
26770004	6	Dissolved Oxygen	19 / 2	7.1	18.9	11.1	0	NA / NA	5	NO	Evaluated	Full
26770004	6	pH	19 / 2	8.2	9	8.5	0	NA / NA	5	NO	Evaluated	Full
26770004	6	Temperature	19 / 2	6.7	28.7	22.7	0	NA / NA	5	NO	Evaluated	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
22770004	6	7	12.60660887	91%	0.752414768	5%	NO	Evaluated	NA

Class BWW1 - 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
14000414	6	Ammonia	11 / 1	0.15	0.04	0.02	0 / 0	NO	Evaluated	Full
14000415	6	Ammonia	11 / 1	0.16	0.04	0.02	0 / 0	NO	Evaluated	Full
14000416	6	Ammonia	11 / 1	0.12	0.04	0.02	0 / 0	NO	Evaluated	Full
22770004	6	Ammonia	26 / 5	0.203	0.06	0.02	0 / 0	NO	Mon	Full
26770002	6	Ammonia	11 / 1	0.08	0.04	0.02	0 / 0	NO	Evaluated	Full
26770004	6	Ammonia	11 / 1	0.08	0.03	0.02	0 / 0	NO	Evaluated	Full

Class BLW - Fish Kill:

The Class BLW use was assessed (evaluated) as “WINOFI” due to a fish kill that occurred in 2017. Because the cause of the fish kill was not identified, or the fish kill was attributed to a non-pollutant cause (e.g., winterkill), the assessment type is “evaluated.” Segments assessed using “evaluated” assessments are placed in Category 3b and are added to the state list of waters in need of further investigation. If no additional fish kills are reported in the segment for a 10 year period (2027), the Category will be changed from 3b to 3a (water not assessed).

Details about the 2017 fish kill can be found here: https://programs.iowadnr.gov/fishkill/Events/942

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)
1052	tissue plug	2019	largemouth bass	10	34.2	0.063
1052	tissue plug	2017	largemouth bass	3	41.1	0.097
1052	tissue plug	2021	muskie	3		0.215
1052	tissue plug	2019	walleye	20	47.9	0.057
Support Level	Full

Monitoring and Methods

Assessment Key Dates

4/23/2018

Monitoring Start

8/31/2020

Monitoring End

8/24/2011

TMDL Completed

6/14/2017

Fish Tissue Monitoring

7/1/2019

Fish Tissue Monitoring

10/4/2022

Fish Tissue Monitoring

8/25/2017

Fish Kill

Methods

140

Incidence of spills and/or fish kills

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