Black Hawk Creek IA 02-CED-546

from Hwy 58 (E 1/2 S27 T88N R14W Black Hawk Co.) to confluence with N. Fk. Black Hawk Cr. in S1 T87N R15W Grundy 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.

Open Segment Map
View assessment methodology in new window

Cycle: 2024
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 11/1/2023 8:12:45 AM
Updated: 12/15/2023 6:03:50 AM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5p - Impairment occurs on a waterbody with a presumptive A1 or B(WW1) use.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Special project/study

TMDL Priority

Tier III

Class BWW1

Aquatic Life - Warm Water Type 1

Not Supported

Biological: low aquatic macroinvertebrate IBI

Support Level

Not Supported

Impairment Code

5b-v - Biological - verified

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2006

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

TMDL Priority

Tier IV

Class HH

Human Health -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive 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 "not supported" based on biological sampling data. All other designated uses were "not assessed." Note: A TMDL for indicator the bacteria impairments in the adjacent downstream segment of Black Hawk Creek (Segment 545) was approved by EPA in 2006. This TMDL, however, did not include this segment (Segment 546); thus, this impairment is considered appropriate for Category 5p of Iowa's 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 2009-2010	13380010	Black Hawk Creek	BHC Site 13
Iowa DNR	6	BIO	See Below	55	Black Hawk Creek	Popp County Access - Hudson

Presumptive Class A1 - Indicator Bacteria: 2009-2010

Site ID	Data Source ID	# Samples / # Years	2009 Geometric Mean	2010 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
13380010	6	21 / 2	1195	765	Yes	18	86%	Yes	Evaluated	Not

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	47c BMIBI BIT	BMIBI Pass/Fail
55	9/22/21	295.1	47c	MS	Art Sub	51	Fair	52	Fail
55	9/19/17	295.1	47c	MS	Art Sub	51	Fair	52	Fail

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	Riffle Stream?	FIBI score	FIBI Class	47c FIBI BIT	FIBI Pass/Fail
55	9/22/21	295.1	47c	MS	No	48	Fair	44	Pass
55	9/19/17	295.1	47c	MS	No	65	Good	44	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Monitored	Fail (0/2)	Fail
Fish	Monitored	Pass (2/2)	Full		Assessment was monitored because the samples used to
Overall	Monitored	Fail	Not	5bv	complete the assessment were collected in the last five years.

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

9/22/2021

Biological Monitoring

6/18/2009

Monitoring Start

11/2/2010

Monitoring End

9/19/2017

Biological Monitoring

Methods

150

Monitoring data more than 5 years old

200

Physical/Chemical Monitoring

320

Benthic macroinvertebrate surveys

330

Fish surveys

420

Indicator bacteria monitoring