West Fork Little Sioux River IA 06-LSR-1598

mouth (S12 T84N R45W Monona Co.) to confluence with a small unnamed tributary near Climbing Hill in S16 T87N R45W Woodbury 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: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Stable

Created: 12/28/2021 6:42:54 AM
Updated: 12/28/2021 6:46:44 AM

Assessment conducted in accordance with Iowa's 2022 IR methodology

Use Support

Class A1

Recreation

Primary contact

Not Supported

Impairments

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier III

Class BWW2

Aquatic Life

Warm Water Type 2

Not Supported

Impairments

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

New

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2022

Impairment Rationale

Violations of chronic criterion

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier III

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 BWW2 use was assessed as "not supported" based on violations of the state water quality chronic criteria for selenium.

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	10970002	West Fork Ditch at Hornick
Iowa DNR	6	BIO	See Below	934	West Fork Little Sioux River	Hornick

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

10970002

0/0/8

227

YES

3 / 3

YES

Monitored

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
10970002	6	36 / 3	7.2	8.4	8.1	0	7	NO	Monitored	Full

Class BWW2 - 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
10970002	6	Ammonia	36 / 3	0.025	2.9	0.2	NA	0 / 0	7	NO	Monitored	Full
10970002	6	Chloride	36 / 3	15	42	20	NA	0 / 0	7	NO	Monitored	Full
10970002	6	Dissolved Oxygen	36 / 3	6.9	13.8	10.4	0	NA / NA	7	NO	Monitored	Full
10970002	6	pH	36 / 3	7.2	8.4	8.1	0	NA / NA	7	NO	Monitored	Full
10970002	6	Sulfate	36 / 3	39	82	62	0	NA / NA	7	NO	Monitored	Full
10970002	6	Temperature	36 / 3	0	26	11	0	NA / NA	7	NO	Monitored	Full

Class BWW2 - 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
10970002	6	Aluminum	14 / 3	15	4.31	3.6	0 / 0	NO	Monitored	Full
10970002	6	Arsenic	13 / 3	3.8	2.5	2.2	0 / 0	NO	Monitored	Full
10970002	6	Cadmium	13 / 3	0.025	0.025	0.025	0 / 0	NO	Monitored	Full
10970002	6	Chromium	13 / 3	1.4	0.9	1	0 / 0	NO	Monitored	Full
10970002	6	Lead	13 / 3	0.42	0.15	0.12	0 / 0	NO	Monitored	Full
10970002	6	Nickel	13 / 3	5.2	3.4	3.1	0 / 0	NO	Monitored	Full
10970002	6	Selenium	13 / 3	13	7.5	7.4	0 / 11	YES	Monitored	Not
10970002	6	Silver	13 / 3	0.025	0.025	0.025	0 / 0	NO	Monitored	Full
10970002	6	Zinc	13 / 3	3.6	2.4	2.6	0 / 0	NO	Monitored	Full

Class BWW2 - Biological Sampling:

Benthic Macroinvertebrates:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	47a BMIBI BIT	BMIBI Pass/Fail
934	8/13/19	399	47d	MO	Floating Art Sub	40	Fair	54	Fail
934	8/18/14	399	47d	MO	Floating Art Sub	58	Good	54	Pass
934	7/30/13	399	47d	MO	Floating Art Sub	61	Good	54	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Pass (2/3)	Full		Assessment was evaluated because the samples used to complete the
Overall	Evaluated	Pass	Full	1	assessment were greater than five years old.

Monitoring and Methods

Assessment Key Dates

1/9/2018

Fixed Monitoring Start Date

12/2/2020

Fixed Monitoring End Date

7/30/2013

Biological Monitoring

8/18/2014

Biological Monitoring

8/13/2019

Biological Monitoring

Methods

150

Monitoring data more than 5 years old

210

Fixed station physical/chemical monitoring (conventional pollutants only)

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

420

Indicator bacteria monitoring