2020 assessment for Duck Creek

Duck Creek IA 01-NEM-1895

from Sec 17-18 line T78N R3E Scott Co. to unnamed trib (SE Sec14 T78N R2E Scott Co.). (Note: Lower segment boundary changed in 2010 to match 2009 WQ Standards.)

2020
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 2016 - 2018
Stream/River Water Quality Data	CY 2016 - 2018
Lake Water Quality Data	CY 2014 - 2018
Biological Sampling Data	CY 2014 - 2018*
Fish Kill Data	CY 2014 - 2018
Fish Tissue Sampling Data	CY 2014 - 2018
Continuous Dissolved Oxygen Sampling Data	CY 2014 - 2018
*Biological sites sampled in both 2013 and 2017 were also assessed.

Open Segment Map
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Overall IR

4 - Water is impaired or threatened and a TMDL has been completed or is not needed.

Trend

Unknown

Created

10/7/2020 7:37:35 AM by

Updated

10/14/2020 7:44:35 AM by

Use Support

Class A1

Presumptive Use

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

High

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Special project/study

Class BWW2

Aquatic Life - Warm Water Type 2

Not Assessed

General Use

General Use water -

Not Assessed

303(d) Delistings for this Cycle

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 use remains assessed as "not supported" due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. All other designated uses were "not assessed". Note: A TMDL for the bacteria impairment in the Duck Creek basin was prepared by Iowa DNR in March 2010 and was approved by U.S. EPA in 2011. Due to completion of the TMDL, the IR category for the presumptive Class A1 recreational use was changed from 5a (impaired; TMDL needed) to 4a (impaired; TMDL approved).

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2008, CY 2013	11820009	Duck Creek site along 110/Buffalo Ave.	DC16

Presumptive Class A1 - Indicator Bacteria: Historical

Site ID	Data Source ID	# Samples / # Years	2008 Geometric Mean	2013 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
11820009	6	35 / 2	1339	1228	Yes	30	86%	Yes	Evaluated	Not

Class BWW2 – No Data

Monitoring and Methods

Assessment Key Dates

4/8/2008

Non-fixed Monitoring Start Date

10/28/2008

Non-fixed Monitoring End Date

5/19/2013

Non-fixed Monitoring Start Date

11/20/2013

Non-fixed Monitoring End Date

3/1/2010

TMDL Completed

Methods

150

Monitoring data more than 5 years old

220

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

420

Indicator bacteria monitoring