Dry Run IA 02-CED-6293

from confluence with unnamed tributary (center S23 T89N R14W Black Hawk Co.) to headwaters in SW1/4 S32 T89N R14W Black Hawk 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 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

Cycle: 2024
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 11/1/2023 8:14:12 AM
Updated: 1/8/2024 2:18:16 PM

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

Slight

Status

Continuing

Source

Agriculture

Source Confidence

N/A

Cycle Added

2012

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Special project/study

TMDL Priority

Tier III

Class BWW1

Presumptive Use

Aquatic Life - Warm Water Type 1

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 use was assessed as "not supported” due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The presumptive Class BWW1 use was assessed as “fully supported” based on limited water quality monitoring data.

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	15070006	DRC9 – Southwest Branch Dry Run Creek at Union Rd.

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
15070006	6	19 / 3	310	528	230	Yes	13	68%	Yes	Evaluated	Not

Presumptive Class A1 - pH: Historical

Site ID	Data Source ID	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
15070006	6	7 / 1	8.1	7.8	7.9	0	0%	No	Evaluated	Full

Presumptive 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
15070006	6	Chloride	7 / 1	29	12	0	0 / 0	0% / 0%	No	Evaluated	Full
15070006	6	Dissolved oxygen	7 / 1	13.5	9.4	8.1	NA / 0	NA / 0%	No	Evaluated	Full
15070006	6	pH	7 / 1	8.1	7.8	7.9	0 / NA	0% / NA	No	Evaluated	Full
15070006	6	Temperature	7 / 1	16.9	12.7	12.1	0 / 0	0% / 0%	No	Evaluated	Full

Monitoring and Methods

Assessment Key Dates

10/24/2012

Monitoring Start

10/28/2014

Monitoring End

Methods

150

Monitoring data more than 5 years old

200

Physical/Chemical Monitoring

420

Indicator bacteria monitoring