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 2016 - 2018
Stream/River Water Quality Data	CY 2016 - 2018
Lake Water Quality Data	CY 2014 - 2018
Biological Sampling Data	CY 2014 - 2018*
Fish Kill Data	CY 2014 - 2018
Fish Tissue Sampling Data	CY 2014 - 2018
Continuous Dissolved Oxygen Sampling Data	CY 2014 - 2018
*Biological sites sampled in both 2013 and 2017 were also assessed.

Open Segment Map
View assessment methodology in new window

Cycle: 2020
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trophic: Eutrophic
Trend: Declining
Trend Comment: Addition of Algal Growth: Chlorophyll a impairment
Created: 8/19/2020 8:46:34 AM
Updated: 10/14/2020 1:22:09 PM

Use Support

Class A1

Recreation - Primary contact

Partially Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Partially 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

Partially Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

New

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

New

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

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 “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 uses are assessed (evaluated) as “partially supported” based on the results of a fish kill investigation and information from the IDNR Fisheries Bureau. Class HH uses are assessed (monitored) as “fully supported” based on fish tissue monitoring. 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

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	21770001	Big Creek Beach (Big Creek State Park)
Iowa DNR	6	WQ	CY 2014-2018	22770004	Big Creek	Lake Deep Point
Iowa DNR	6	WQ	CY 2015-2018	26770002	Big Creek 319 (BCL4)	TMDL north arm sampling point
Iowa DNR	6	WQ	CY 2015-2018	26770003	Big Creek 319 (BCL3)	TMDL central sampling point
Iowa DNR	6	WQ	CY 2015-2018	26770004	Big Creek 319 (BCL5)	TMDL west arm sampling point
Iowa DNR		FT	See Below	52	Big Creek

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
21770001	6	21 / 3	100.82	107.78	36.02	No	7	33%	YES	Monitored	Partial
22770004	6	18 / 3	5	6.6	11.08	No	0	0%	NO	Monitored	Full
26770002	6	20 / 3	14.2	28.62	58.85	No	3	15%	NO	Monitored	Full
26770003	6	20 / 3	7.94	13.49	11.03	No	0	0%	NO	Monitored	Full
26770004	6	20 / 3	9.31	23.37	40.39	No	1	5%	NO	Monitored	Full

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
22770004	6	15 / 5	8.72	8.08	8	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
22770004	6	Chlorophyll a TSI	39 / 5	36	79	64	NO	Monitored	Full
26770002	6	Chlorophyll a TSI	24 / 4	48	83	68	YES	Monitored	Not
26770003	6	Chlorophyll a TSI	24 / 4	50	78	68	YES	Monitored	Not
26770004	6	Chlorophyll a TSI	24 / 4	52	79	70	YES	Monitored	Not
22770004	6	Secchi TSI	15 / 5	41	70	60	NO	Monitored	Full
22770004	6	Total Phosphorus TSI	39 / 5	54	80	67	NA	NA	NA
26770002	6	Total Phosphorus TSI	24 / 4	61	83	73	NA	NA	NA
26770003	6	Total Phosphorus TSI	24 / 4	61	79	72	NA	NA	NA
26770004	6	Total Phosphorus TSI	24 / 4	61	82	74	NA	NA	NA
22770004	6	Inorganic suspended solids	15 / 5	0.3	10	2	NA	NA	NA

Class BWW1 - 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
22770004	6	Ammonia	15 / 5	0.162	0.06	0.05	0 / 0	0% / 0%	NO	Monitored	Full
22770004	6	Dissolved oxygen	15 / 5	14.75	8.73	9.2	NA / 2	NA / 13%	NO	Monitored	Full
22770004	6	pH	15 / 5	8.72	8.08	8	0 / NA	0% / NA	NO	Monitored	Full
22770004	6	Temperature	15 / 5	27.7	22	23.7	0 / 0	0% / 0%	NO	Monitored	Full

Class BWW1 - 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
22770004	6	11	74.926	99.9 %	1.193	35.7 %	NO	Evaluated	NA

Class BLW - Fish Kill:

The Class BLW uses are assessed (evaluated) as “partially supported” due to fish kills that occurred in August of 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, 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

Date

Species Name

Biopart

# in sample

chlordane result

chlordane violation?

PCBs result

PCBs violation?

Hg result

Hg violation?

Assessment Type

Support Level

6/14/17

largemouth bass

plug

0.097

Monitored

Full

Monitoring and Methods

Assessment Key Dates

5/27/2014

Fixed Monitoring Start Date

10/22/2018

Fixed Monitoring End Date

8/24/2011

TMDL Completed

6/14/2017

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