2022 Final assessment for Black Hawk Creek

Black Hawk Creek IA 02-CED-545

mouth (S22 T89N R13W Black Hawk Co.) to Hwy 58 in E 1/2 S27 T88N R14W Black Hawk Co.)

Assessment Cycle

2022

Release Status

Final

Data Collection Period

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 2018 - 2020
Stream/River Water Quality Data	CY 2018 - 2020
Lake Water Quality Data	CY 2016 - 2020
Biological Sampling Data	CY 2016 - 2020*
Fish Kill Data	CY 2016 - 2020
Fish Tissue Sampling Data	CY 2016 - 2020
Continuous Dissolved Oxygen Sampling Data	CY 2016 - 2020
*Biological sites sampled in both 2015 and 2019 were also assessed.

Overall IR Category: 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Trend: Unknown

Created: 12/22/2021 12:59:23 PM
Updated: 12/22/2021 1:02:14 PM

Assessment conducted in accordance with Iowa's 2022 IR methodology

Use Support

Class A1

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

4a - Pollutant-caused impairment. TMDL has been completed.

Cause Magnitude

Slight

Status

Continuing

Source

Agriculture

Source Confidence

N/A

Cycle Added

2002

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

Class BWW1

Fully Supported

Class HH

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed as "not supported" due to levels of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW1 use was assessed as "fully supported" based on water quality monitoring data and biological sampling data. All other designated uses were "not assessed." Note: A TMDL for indicator bacteria in this segment of Black Hawk Creek was prepared by DNR and approved by EPA in 2006. Because all Section 303(d) impairments identified for this assessment/listing cycle (indicator bacteria) were addressed by the TMDL, this waterbody was placed in IR Category 4a (impaired; TMDL approved) of the current Integrated Report.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2018-2020	10070004	Black Hawk Creek at Waterloo
CRWQ	23	WQ	CY 2018-2020	99990060	Blackhawk Creek
Iowa DNR	6	BIO	See Below	1155	Black Hawk Creek	Ridgeway Ave SW of Waterloo

Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2018/ 2019/2020)

2018 Geometric Mean

2019 Geometric Mean

2020 Geometric Mean

Violates Annual Geometric Mean?

# 2018 SSM violations / SSM Violations needed for impairment

# 2019 SSM violations / SSM Violations needed for impairment

# 2020 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

10070004

7/8/8

571

302

YES

6 / 3

4 / 3

3 / 3

YES

Monitored

Not

99990060

5/5/5

826

159

185

YES

4 / NA

1 / NA

3 / NA

Evaluated

Not

Class A – 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
10070004	6	36 / 3	7.1	8.4	8	0	7	NO	Monitored	Full
99990060	23	14 / 3	7.34	8.44	7.96	0	4	NO	Monitored	Full

Class BWW1 - Conventional 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
10070004	6	Ammonia	36 / 3	0.025	0.2	0.04	NA	0 / 0	7	NO	Monitored	Full
10070004	6	Chloride	36 / 3	14	33	21	NA	0 / 0	7	NO	Monitored	Full
99990060	23	Chloride	15 / 3	12.6	25	20.1	NA	0 / 0	4	NO	Monitored	Full
10070004	6	Dissolved Oxygen	36 / 3	7.7	13.8	10.4	0	NA / NA	7	NO	Monitored	Full
99990060	23	Dissolved Oxygen	15 / 3	6.5	12.7	8.6	0	NA / NA	4	NO	Monitored	Full
10070004	6	pH	36 / 3	7.1	8.4	8	0	NA / NA	7	NO	Monitored	Full
99990060	23	pH	14 / 3	7.34	8.44	7.96	0	NA / NA	4	NO	Monitored	Full
10070004	6	Sulfate	36 / 3	8.8	29	17.1	0	NA / NA	7	NO	Monitored	Full
99990060	23	Sulfate	15 / 3	6.7	27.2	17	0	NA / NA	4	NO	Monitored	Full
10070004	6	Temperature	36 / 3	0.1	24.8	11.3	0	NA / NA	7	NO	Monitored	Full
99990060	23	Temperature	15 / 3	9.1	24.4	19.6	0	NA / NA	4	NO	Monitored	Full

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
10070004	6	Aluminum	14 / 3	4.2	1	0.6	0 / 0	NO	Monitored	Full
10070004	6	Arsenic	13 / 3	0.96	0.66	0.65	0 / 0	NO	Monitored	Full
10070004	6	Cadmium	13 / 3	0.11	0.04	0.02	0 / 0	NO	Monitored	Full
10070004	6	Chromium	13 / 3	1.2	0.8	0.8	0 / 0	NO	Monitored	Full
10070004	6	Lead	13 / 3	0.24	0.1	0.1	0 / 0	NO	Monitored	Full
10070004	6	Nickel	13 / 3	2.9	2.2	2.3	0 / 0	NO	Monitored	Full
10070004	6	Silver	13 / 3	0.025	0.025	0.025	0 / 0	NO	Monitored	Full
10070004	6	Zinc	13 / 3	4.4	2.3	2.2	0 / 0	NO	Monitored	Full

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	47c BMIBI BIT	BMIBI Pass/ Fail
1155	8/21/19	332	47c	MS	Art Sub	74	Good	52	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Pass (1/1)	Full
Overall	Evaluated	Pass	Full	1	Assessment was evaluated because it was based on a single sample.

Class HH – No Data

Monitoring and Methods

Assessment Key Dates

1/8/2018	Fixed Monitoring Start Date
12/7/2020	Fixed Monitoring End Date
11/9/2006	TMDL Completed
8/21/2019	Biological Monitoring

Methods

230	Fixed station physical/chemical (conventional plus toxic pollutants)
315	Regional reference site approach
320	Benthic macroinvertebrate surveys
420	Indicator bacteria monitoring

Water Quality Assessments

Impaired Waters List

Black Hawk Creek IA 02-CED-545

Assessment Summary

Assessment Explanation

Assessment Key Dates

Methods