2020 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

2020

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 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.

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

Created: 6/25/2020 10:00:29 AM
Updated: 10/16/2020 9:04:39 AM

Assessment conducted in accordance with Iowa's 2020 IR methodology

Use Support

Class A1

Partially Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Partially 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

Fully Supported

General Use

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed as "partially supported" due to levels of indicator bacteria (E. coli) that violated state water quality standards. The Class BWW1 use was assessed as "fully supported" based on water quality data monitoring. The Class HH use was assessed as "fully supported" based on water quality monitoring data. 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

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	BioNet Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2016-2018	10070004		Black Hawk Creek at Waterloo	DNR ambient station at Ridgeway Avenue SW of Waterloo

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
10070004	6	22 / 3	357.51	616.85	571.42	Yes	16	73%	Yes	Monitored	Partial

Class A - pH

Site ID	Data Source ID	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
10070004	6	36 / 3	8.3	8.1	8.1	0	0%	No	Monitored	Full

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
10070004	6	Ammonia	36 / 3	0.2	0.04	0.02	0 / 0	0% / 0%	No	Monitored	Full
10070004	6	Chloride	36 / 3	33	22	22	0 / 0	0% / 0%	No	Monitored	Full
10070004	6	Dissolved oxygen	36 / 3	14	10.3	10.4	NA / 0	NA / 0%	No	Monitored	Full
10070004	6	pH	36 / 3	8.3	8.1	8.1	0 / NA	0% / NA	No	Monitored	Full
10070004	6	Sulfate	36 / 3	33	18	18	0 / NA	0% / NA	No	Monitored	Full
10070004	6	Temperature	36 / 3	23.5	11.4	11.7	0 / 0	0% / 0%	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	% Acute/ Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
10070004	6	Aluminum	9 / 2	4.2	1.437	1.2	0 / 0	0% / 0%	No	Evaluated	Full
10070004	6	Arsenic	9 / 2	0.96	0.74	0.78	0 / 0	0% / 0%	No	Evaluated	Full
10070004	6	Cadmium	9 / 2	0.025	0.025	0.025	0 / 0	0% / 0%	No	Evaluated	Full
10070004	6	Chromium	9 / 2	1.2	0.79	0.78	0 / 0	0% / 0%	No	Evaluated	Full
10070004	6	Copper	9 / 2	0.98	0.59	0.54	0 / 0	0% / 0%	No	Evaluated	Full
10070004	6	Lead	9 / 2	0.12	0.054	0.05	0 / 0	0% / 0%	No	Evaluated	Full
10070004	6	Nickel	9 / 2	2.3	2	2	0 / 0	0% / 0%	No	Evaluated	Full
10070004	6	Selenium	9 / 2	2.2	1.55	1.5	0 / 0	0% / 0%	No	Evaluated	Full
10070004	6	Zinc	9 / 2	4.4	1.8	1.1	0 / 0	0% / 0%	No	Evaluated	Full

Class HH-F - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	Number of Non - Detects	Mean Value > Criterion or MCL	Assessment Type	Support Level
10070004	6	Cadmium	9 / 2	0.025	0.025	0.025	9	No	Evaluated	Full
10070004	6	Chromium	9 / 2	1.2	0.79	0.78	0	No	Evaluated	Full
10070004	6	Copper	9 / 2	0.98	0.59	0.54	0	No	Evaluated	Full
10070004	6	Nickel	9 / 2	2.3	2	2	0	No	Evaluated	Full
10070004	6	Selenium	9 / 2	2.2	1.55	1.5	0	No	Evaluated	Full
10070004	6	Zinc	9 / 2	4.4	1.8	1.1	0	No	Evaluated	Full

Monitoring and Methods

Assessment Key Dates

1/7/2016	Fixed Monitoring Start Date
12/11/2018	Fixed Monitoring End Date
11/9/2006	TMDL Completed

Methods

230	Fixed station physical/chemical (conventional plus toxic pollutants)
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