2024 assessment for Elk Creek

Elk Creek IA 01-TRK-175

mouth (S36 T92N R4W Clayton Co.) to confluence with Steeles Br. in S26 T91N R4W Clayton Co.

2024
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

Overall IR

5 - Water is impaired or threatened and a TMDL is needed.

Trend

Unknown

Created

11/1/2023 8:14:02 AM by

Updated

12/14/2023 11:02:14 AM by

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

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2014

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Watershed project monitoring

TMDL Priority

Tier III

Class BWW1

Aquatic Life - Warm Water Type 1

Fully Supported

Class HH

Human Health -

Not Assessed

303(d) Delistings for this Cycle

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 use was assessed as “not supported” due to violations of Iowa water quality criteria for indicator bacteria (E. coli). The Class BWW1 use was assessed as “fully supported” based 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 2012-2014	15220012	Elk Creek @ Colesburg Rd/X3C	ELK10

Presumptive Class A1 - Indicator Bacteria: Historical

Site ID	Data Source ID	# Samples / # Years	2012 Geometric Mean	2013 Geometric Mean	2014 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
15220012	6	24 / 3	386	2480	239	Yes	12	50%	Yes	Evaluated	Not

Class BWW1 - Binomial Parameters: Historical

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	% Acute/ Chronic Violations	Significantly >10% Violations	Assessment Type	Support Level
15220012	6	Ammonia	12 / 2	0.35	0.09	0.05	0 / 0	0% / 0%	No	Evaluated	Full
15220012	6	Chloride	16 / 2	33	32.25	33	0 / 0	0% / 0%	No	Evaluated	Full
15220012	6	Dissolved oxygen	23 / 3	12	9.8261	10	NA / 0	NA / 0%	No	Evaluated	Full
15220012	6	pH	21 / 3	9.06	8.36	8.33	1 / NA	5% / NA	No	Evaluated	Full

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

4/4/2012

Monitoring Start

11/5/2014

Monitoring End

Methods

150

Monitoring data more than 5 years old

200

Physical/Chemical Monitoring

420

Indicator bacteria monitoring