Thompson River IA 05-GRA-1351

from the Iowa/Missouri state line to confluence with Long Cr. in SW 1/4 S8 T69N R26W Decatur 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: 12/27/2021 1:57:19 PM
Updated: 12/27/2021 2:02:11 PM

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

2004

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier III

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 levels of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW1 use was assessed as "fully supported" based on biological sampling data and on water quality monitoring data. All other designated uses were "not assessed."

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	10270001	Thompson Fork - Grand River at Davis City
Iowa DNR	6	BIO	See Below	266	Thompson River	Decatur City
Iowa DNR	6	BIO	See Below	932	Thompson Fork - Grand River at Davis City

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

10270001

3/3/8

367

1084

122

YES

2 / NA

2 / 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
10270001	6	35 / 3	6.9	8.3	7.7	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
10270001	6	Ammonia	35 / 3	0.02	0.27	0.07	NA	0 / 0	7	NO	Monitored	Full
10270001	6	Chloride	36 / 3	5	24	12	NA	0 / 0	7	NO	Monitored	Full
10270001	6	Dissolved Oxygen	36 / 3	6	13.4	9.7	0	NA / NA	7	NO	Monitored	Full
10270001	6	pH	35 / 3	6.9	8.3	7.7	0	NA / NA	7	NO	Monitored	Full
10270001	6	Sulfate	36 / 3	4	57	22	0	NA / NA	7	NO	Monitored	Full
10270001	6	Temperature	36 / 3	0	30.9	12.2	0	NA / NA	7	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	>1 Acute / Chronic Violation	Assessment Type	Support Level
10270001	6	Aluminum	14 / 3	17	3.37	0.88	0 / 0	NO	Monitored	Full
10270001	6	Arsenic	13 / 3	4.5	1.8	1.4	0 / 0	NO	Monitored	Full
10270001	6	Cadmium	13 / 3	0.3	0.0462	0.025	0 / 1	NO	Monitored	Full
10270001	6	Chromium	13 / 3	2	0.66	0.66	0 / 0	NO	Monitored	Full
10270001	6	Lead	13 / 3	9.5	0.8	0.1	0 / 1	NO	Monitored	Full
10270001	6	Nickel	13 / 3	10	3.9	3.6	0 / 0	NO	Monitored	Full
10270001	6	Silver	13 / 3	0.025	0.025	0.025	0 / 0	NO	Monitored	Full
10270001	6	Zinc	13 / 3	17	2.69	1.3	0 / 0	NO	Monitored	Full

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	40a BMIBI BIT	BMIBI Pass/Fail
932	7/20/18	701	40a	MO	Hess	48	Fair	41	Pass
266	7/27/17	602	40a	MO	Hess	61	Good	41	Pass

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	Riffle Stream?	FIBI score	FIBI Class	40a FIBI BIT	FIBI Pass/Fail
266	7/27/17	602	40a	MO	NA	37	Fair	33	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Pass (2/2)	Full
Fish	Evaluated	Pass (1/1)	Full		Assessment was evaluated because the drainage areas of the
Overall	Evaluated	Pass	Full	1	sites were greater than the calibrated range.

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

7/27/2017

Biological Monitoring

7/20/2018

Biological Monitoring

1/2/2018

Fixed Monitoring Start Date

12/1/2020

Fixed Monitoring End Date

Methods

230

Fixed station physical/chemical (conventional plus toxic pollutants)

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys

380

Quantitative physical habitat assessment

420

Indicator bacteria monitoring