Big Sioux River IA 06-BSR-1526

from confluence with Ninemile Cr. (S25 T100N R49W Lyon Co.) to the Iowa / Minnesota state line at N line of S4 T100N R49W Lyon 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.

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Cycle: 2022
Release Status: Final
Overall IR: 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Trend: Stable
Created: 12/29/2021 3:03:55 PM
Updated: 12/29/2021 3:05:02 PM

Use Support

Class A1

Recreation - Primary contact

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

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2012

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: adjacent state

Class BWW1

Aquatic Life - Warm Water Type 1

Fully Supported

Class HH

Human Health -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed as “not supported” due to violations of Iowa’s water quality criteria for indicator bacteria (E. coli). The Class BWW1 use was assessed as "fully supported" based on the results of ambient chemical/physical water quality monitoring. All other designated uses were “not assessed.” Note: A TMDL for pathogen indicators in this segment of the Big Sioux River was prepared by DNR and the South Dakota Dept. of Environment & Natural Resources; this TMDL was approved by EPA in January 2008. Because all Section 303(d) impairments identified for the current assessment/listing cycle were addressed by the TMDL, this waterbody remains in IR Category 4a (impaired; TMDL approved).

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
SDAK	16	WQ	CY 2018-2020	460831	Big Sioux River

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

460831

5/5/5

123

168

YES

2 / NA

0 / NA

Evaluated

Not

Class A1 – 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
460831	16	36 / 3	7.8	8.7	8.1	0	7	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
460831	16	Ammonia	36 / 3	0.02	1.22	0.11	NA	0 / 0	7	NO	Monitored	Full
460831	16	Dissolved Oxygen	36 / 3	7.8	21.6	13.4	0	NA / NA	7	NO	Monitored	Full
460831	16	pH	36 / 3	7.8	8.7	8.1	0	NA / NA	7	NO	Monitored	Full
460831	16	Temperature	36 / 3	1	28	11	0	NA / NA	7	NO	Monitored	Full

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

1/17/2018

Fixed Monitoring Start Date

12/16/2020

Fixed Monitoring End Date

1/23/2008

TMDL Completed

Methods

230

Fixed station physical/chemical (conventional plus toxic pollutants)

420

Indicator bacteria monitoring