Twin Springs Creek IA 01-UIA-273

mouth (S17 T98N R8W Winneshiek Co.) to springs in Twin Springs Parks (S20 T98N R8W Winneshiek 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 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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Cycle: 2020
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 10/1/2020 9:36:12 AM
Updated: 10/15/2020 10:59:19 AM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Partially Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Partially Supported

Impairment Code

5p - Impairment occurs on a waterbody with a presumptive A1 or B(WW1) use.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2012

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Watershed project monitoring

TMDL Priority

Tier III

Class A2

Presumptive Use

Recreation - Secondary contact

Fully Supported

Class BCW1

Aquatic Life - Cold Water Type 1

Fully Supported

Class HH

Human Health -

Not Assessed

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 use remains assessed as “partially supported” due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The presumptive Class A2 use remains assessed as “fully supported” based on water quality monitoring data. The Class BCW1 use remains assessed as "fully supported" based on the trout reproduction in Iowa streams summary prepared by the DNR Fisheries Bureau and water quality monitoring data. All other designated uses are “not assessed”.

Assessment Explanation

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2010-2011	15960030	Dry Run Creek Watershed Site 18

Presumptive Class A1 - Indicator Bacteria: Historical

Site ID	Data Source ID	# Samples / # Years	2010 Geometric Mean	2011 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
15960030	6	29 / 2	200	361	Yes	13	45%	Yes	Evaluated	Partial

Presumptive Class A2 - Indicator Bacteria: Historical

Site ID	Data Source ID	# Samples / # Years	2010 Geometric Mean	2011 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
15960030	6	29 / 2	200	361	No	5	17%	No	Evaluated	Full

Class BCW1 - Conventional Parameters: Historical

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	# Acute / Chronic Violations	% Acute/ Chronic Violations	Significantly >10% Violations	Assessment Type	Support Level
15960030	6	Ammonia	30 / 2	NA	0 / 0	0% / 0%	No	Evaluated	Full
15960030	6	Dissolved oxygen	32 / 2	4.2	NA / 2	NA / 6%	No	Evaluated	Full
15960030	6	pH	30 / 2	NA	0 / NA	0% / 0%	No	Evaluated	Full
15960030	6	Temperature	30 / 2	NA	0 / 0	0% / 0%	No	Evaluated	Full

Class BCW1 – Trout Natural Reproduction:

Based on the January 2020 trout reproduction in Iowa streams summary prepared by the DNR Fisheries Bureau, the Class BCW1 coldwater aquatic life use of Twin Springs Creek was assessed as "fully supported". According to the updated summary, this stream was placed in Category I: streams that exhibit consistent natural reproduction and maintain a wild population of one or more trout species without any stocking.

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

4/21/2010

Fixed Monitoring Start Date

10/10/2011

Fixed Monitoring End Date

1/1/2020

Biological Monitoring

Methods

120

Surveys of fish and game biologists/other professionals

220

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

330

Fish surveys

420

Indicator bacteria monitoring