Tipton Creek IA 02-IOW-755

from confluence with unnamed tributary (SE 1/4 S17 T87N R21W Hardin Co.) to confluence with New York Branch in S32 T88N R22W Hardin 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 2014 - 2016
Stream/River Water Quality Data	CY 2014 - 2016
Lake Water Quality Data	CY 2012 - 2016
Biological Sampling Data	CY 2012 - 2016*
Fish Kill Data	CY 2012 - 2016
Fish Tissue Sampling Data	CY 2012 - 2016
Continuous Dissolved Oxygen Sampling Data	CY 2012 - 2016
*Biological sites sampled in both 2011 and 2015 were also assessed.

Open Segment Map
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Cycle: 2018
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 8/2/2019 9:54:54 AM
Updated: 8/2/2019 9:56:52 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

2010

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: USDA/National Lab for Ag. and Environment

TMDL Priority

Tier III

Class BWW2

Aquatic Life - Warm Water Type 2

Not Assessed

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 (primary contact recreation) uses are assessed as "not supported" due to levels of indicator bacteria that violate state water quality criteria. The source of data for this assessment is the results of monitoring from May 2010 through November 2014 conducted by the National Laboratory for Agriculture and the Environment (NLAE), Ames, IA, at station TC313 approximately 3 miles SW of Buckeye in Hardin County. The Class B(WW2) aquatic life uses remain “not assessed” due to the lack of sampling data in this segment.

Assessment Explanation

The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on results of ambient monitoring for indicator bacteria (E. coli). The following table summarized recreation season geometric means of E. coli at station TC313 over the 2010-2014 period.

Summary of recreation season (March 15-November 15) geometric means of indicator bacteria (E. coli) at station TC313 on Tipton Creek approximately 3 miles SW of Buckeye in Hardin County. Geometric means are number of organisms per 100 ml.
Station:	2010	2011	2012	2013	2014	No. samples, 2010-14	No. > 235, 2010-14	% of samples > 235
TC313	143.0	135.8	218.2	35.1	84.7	37	12	32.4%

The geometric means for the 2010, 2011, and 2012 recreation seasons all slightly exceeded the Class A1 criterion of 126 orgs/100 ml. The 2013 and 2014 geometric means, however, were well below (met) the Class A1 standard. Twelve of the 37 samples (32.4%) collected over the 2010-2014 period exceeded the single-sample maximum criterion of 235 E. coli organisms/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and according to DNR’s assessment/listing methodology, if the geometric mean level of E. coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).

Monitoring and Methods

Assessment Key Dates

5/4/2010

Fixed Monitoring Start Date

11/5/2014

Fixed Monitoring End Date

Methods

150

Monitoring data more than 5 years old

420

Indicator bacteria monitoring