Flood Creek IA 02-SHL-788

mouth (S27 T93N R16W Butler Co.) to confluence with Beaver Cr. in S36 T95N R17W Floyd 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 9:37:59 AM
Updated: 8/2/2019 9:39:33 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

2008

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier III

Class BWW2

Aquatic Life - Warm Water Type 2

Fully Supported

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 uses remain assessed as “partially supported” due to high levels of indicator bacteria. The Class B(WW2) aquatic life uses remain assessed as "fully supported" although this stream suffers from naturally-occurring problems with flow stability (i.e., intermittency). The source of data for this assessment remains the results of DNR/SHL ambient water quality monitoring conducted from May 2004 through September 2006 at DNR station 10340002 near Greene. DNR/SHL ambient monitoring at this station was terminated in September 2006. This assessment is the same as that developed for the previous assessment/listing cycles.

Assessment Explanation

The presumptive Class A1 uses remain assessed as "partiallysupported" based on results of ambient monitoring for indicator bacteria (E. coli). The geometric mean level of indicator bacteria (E. coli) in the 23 samples collected during the recreational seasons of 2004 through 2006 (213 orgs/100ml) slightly exceeded the Iowa Class A1 water quality criterion of 126 orgs/100ml. Eight of the 23 samples (35%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/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 3-35of U.S. EPA 1997b).

The Class B(WW2) aquatic life uses remain assessed (evaluated) as “fully supported” based on results of routine ambient water quality monitoring. This stream is known to be prone to intermittency; the causes of this intermittency are believed to be naturally-occurring. Despite this problem, results of ambient water quality monitoring conducted by DNR/SHL near Greene, Iowa, during the 2004-2006 assessment period continue to suggest “full support” of the Class B(WW2) aquatic life uses. None of the samples collected violated state criteria for dissolved oxygen (25 samples), temperature (25 samples), pH (24 samples), or ammonia-nitrogen (22 samples); none of the six samples analyzed for pesticides and toxic metals contained levels above the Class B(WW2) criteria. The results of this monitoring suggest that, when Flood Creek has sufficient water, the water quality is relatively good.

Monitoring and Methods

Assessment Key Dates

5/24/2004

Fixed Monitoring Start Date

9/5/2006

Fixed Monitoring End Date

Methods

150

Monitoring data more than 5 years old

230

Fixed station physical/chemical (conventional plus toxic pollutants)

420

Indicator bacteria monitoring