Sixmile Creek IA 06-BSR-1533

mouth (S28T94N R48W Sioux Co.) to confluence with unnamed tributary in S19 T95N R46W Sioux 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 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.

Open Segment Map
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Cycle: 2022
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 12/30/2021 10:25:55 AM
Updated: 12/30/2021 10:28:28 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

High

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Moderate

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Data Source

TMDL monitoring: Iowa DNR

TMDL Priority

Tier III

Class BWW2

Aquatic Life - Warm Water Type 2

Not Supported

Biological: low fish & invert IBIs- cause unknown

Support Level

Not Supported

Impairment Code

5b-t - Biological - tentative

Cause Magnitude

High

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

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 BWW2 use was assessed as “not supported” based on biological 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 2002-2003	11840003	Sixmile Creek nr Chatsworth (8)
Iowa DNR	6	BIO	See Below	175	Sixmile Creek	Hawarden – Cleveland Ave
Iowa DNR	6	BIO	See Below	176	Sixmile Creek	Hawarden – Cherry Ave

Presumptive Class A1 - Indicator Bacteria:

Site ID	Data Source ID	# Samples / # Years	2002-2003 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
11840003	6	21 / 2	1212	Yes	16	76%	Yes	Evaluated	Not

Class BWW2 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/ Thermal	BM Sample Gear	BMIBI score	BMIBI Class	47a BMIBI BIT	BMIBI Pass/ Fail
175	8/3/00	72	47a	MO/WW	ArtSub	46	Fair	54	Fail
176	8/2/00	94	47a	MO/WW	ArtSub	58	Good	54	Pass

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/ Thermal	Riffle Stream?	FIBI score	FIBI Class	47a FIBI BIT	FIBI Pass/ Fail
175	8/3/00	72	47a	MO/WW	NA	10	Poor	43	Fail
176	8/2/00	94	47a	MO/WW	NA	2	Poor	43	Fail

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (1/2)	Not
Fish	Evaluated	Fail (0/2)	Not
Overall	Evaluated	Fail	Not	5bt	Assessment was evaluated because it was based on samples not collected in the last five years.

Monitoring and Methods

Assessment Key Dates

3/19/2002

Non-fixed Monitoring Start Date

12/16/2003

Non-fixed Monitoring End Date

8/2/2000

Biological Monitoring

8/3/2000

Biological Monitoring

Methods

150

Monitoring data more than 5 years old

220

Non-fixed station physical/chemical monitoring (conventional pollutant only)

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys

420

Indicator bacteria monitoring