Big Hollow Lake IA 02-ICD-6496

Approximately 5 miles southwest of Mediapolis IA in S-17 T-71N R-3W Des Moines Co.

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.

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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 8:13:41 AM
Updated: 12/27/2023 3:04:02 PM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2016

Impairment Rationale

Significantly > 10% of samples fail to meet criterion

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier II

Turbidity: Secchi Disk Transparency

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

Continuing

Source

Other: Sediment Resuspension

Source Confidence

Low

Cycle Added

2022

Impairment Rationale

Narrative criteria violation: aesthetically objectionable conditions

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier II

Algal Growth: Chlorophyll a

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

New

Source

Agriculture

Source Confidence

Low

Cycle Added

2024

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

Not Supported

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2016

Impairment Rationale

Significantly > 10% of samples fail to meet criterion

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier II

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 the presence of aesthetically objectionable conditions caused by non-algal turbidity, algal blooms and violations of the Class A1 criterion for pH. The Class BLW use was assessed (monitored) as “not supported” due to violations of the Class BLW criterion for pH. The Class HH (fish consumption) use was assessed (evaluated) as "fully supported" based on turtle tissue sampling data.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2019-2019	14000296	Big Hollow 1
Iowa DNR	6	WQ	CY 2018-2022	22290002	Big Hollow Lake
Iowa DNR	6	FT	See Below	1344	Big Hollow Lake	Big Hollow Recreational Area

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
14000296	6	11 / 1	7.6	9.8	8.8	4	3	YES	Mon	Not
22290002	6	23 / 4	7.4	9.7	8.5	5	5	YES	Mon	Not

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
14000296	6	Chlorophyll a TSI	12 / 1	31	77	68	YES	Evaluated	Not
22290002	6	Chlorophyll a TSI	24 / 4	30	76	66	YES	Mon	Not
14000296	6	Secchi TSI	12 / 1	46	81	64	NO	Evaluated	Full
22290002	6	Secchi TSI	24 / 4	36	80	68	YES	Mon	Not
14000296	6	Total Phosphorus TSI	12 / 1	61	88	76	NA	NA	NA
22290002	6	Total Phosphorus TSI	24 / 4	57	90	74	NA	NA	NA
22290002	6	Inorganic suspended solids	12 / 4	0.6	8	1.9	NA	NA	NA

Class BLW - 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
14000296	6	Dissolved Oxygen	11 / 1	7.6	18.8	11.7	0	NA / NA	3	NO	Mon	Full
22290002	6	Dissolved Oxygen	23 / 4	6.4	20.6	10.6	0	NA / NA	5	NO	Mon	Full
14000296	6	pH	11 / 1	7.6	9.8	8.8	4	NA / NA	3	YES	Mon	Not
22290002	6	pH	23 / 4	7.4	9.7	8.5	5	NA / NA	5	YES	Mon	Not
14000296	6	Temperature	11 / 1	10.1	28	21.6	0	NA / NA	3	NO	Mon	Full
22290002	6	Temperature	23 / 4	13.6	28.4	23	0	NA / NA	5	NO	Mon	Full

Class BLW - 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
14000296	6	Ammonia	10 / 1	0.35	0.1	0.02	0 / 0	NO	Mon	Full
22290002	6	Ammonia	22 / 4	0.37	0.07	0.02	0 / 0	NO	Mon	Full

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)
1344	shoulder	2015	snapping turtle	3	28.3	0.16	0.02	0.06
Support Level	Full

Monitoring and Methods

Assessment Key Dates

5/21/2018

Monitoring Start

9/6/2022

Monitoring End

8/13/2015

Fish Tissue Monitoring

Methods

200

Physical/Chemical Monitoring

260

Fish tissue analysis

420

Indicator bacteria monitoring