Unnamed Tributary to Silver Creek IA 01-UIA-6569

from mouth (T99N R11W Sec13) to headwaters (T99N R11W Sec23) Howard 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.

Open Segment Map
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Cycle: 2022
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 1/11/2022 7:32:30 AM
Updated: 1/11/2022 7:36:18 AM

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

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

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 remains assessed as "not supported" due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The presumptive Class BWW1 use remains assessed as “fully supported” based 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 2011-2012	15450017	Tributary to Silver Creek DS of WWTP	Site 2
Iowa DNR	6	WQ	CY 2011-2012	15450018	Tributary to Silver Creek US of WWTP	Site 1

Presumptive Class A1 - Indicator Bacteria: 2011-2012

Site ID	Data Source ID	# Samples / # Years	2011 Geometric Mean	2012 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
15450017	6	22 / 2	272	2186	Yes	15	68%	Yes	Evaluated	Not
15450018	6	22 / 2	315	557	Yes	16	73%	Yes	Evaluated	Not

Presumptive Class A1 - pH: 2011

Site ID	Data Source ID	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
15450017	6	16 / 1	8.2	7.7	7.7	0	0%	No	Evaluated	Full
15450018	6	16 / 1	8.4	8.1	8.1	0	0%	No	Evaluated	Full

Presumptive Class BWW1 - Conventional Parameters: 2011

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
15450017	6	Ammonia	14 / 1	1.5	0.24	0.11	0 / 0	0% / 0%	No	Evaluated	Full
15450017	6	Dissolved oxygen	16 / 1	10.3	8.7	8.9	NA / 0	NA / 0%	No	Evaluated	Full
15450017	6	pH	16 / 1	8.2	7.7	7.7	0 / NA	0% / NA	No	Evaluated	Full
15450017	6	Temperature	16 / 1	18	13.4	14	0 / 0	0% / 0%	No	Evaluated	Full
15450018	6	Ammonia	15 / 1	0.08	0.05	0.05	0 / 0	0% / 0%	No	Evaluated	Full
15450018	6	Dissolved oxygen	16 / 1	15.3	10.4	10.2	NA / 0	NA / 0%	No	Evaluated	Full
15450018	6	pH	16 / 1	8.4	8.1	8.1	0 / NA	0% / NA	No	Evaluated	Full
15450018	6	Temperature	16 / 1	16.4	11.3	11.3	0 / 0	0% / 0%	No	Evaluated	Full

Monitoring and Methods

Assessment Key Dates

4/18/2011

Non-fixed Monitoring Start Date

7/11/2012

Non-fixed Monitoring End Date

Methods

150

Monitoring data more than 5 years old

220

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

420

Indicator bacteria monitoring