Middle Fork Catfish Creek IA 01-TRK-128

mouth (S1 T88N R2E Dubuque Co.) to west line of S30 T89N R2E Dubuque 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 2012 - 2014
Stream/River Water Quality Data	CY 2012 - 2014
Lake Water Quality Data	CY 2010 - 2014
Biological Sampling Data	CY 2010 - 2014*
Fish Kill Data	CY 2010 - 2014
Fish Tissue Sampling Data	CY 2010 - 2014
Continuous Dissolved Oxygen Sampling Data	CY 2010 - 2014
*Biological sites sampled in both 2009 and 2013 were also assessed.

Open Segment Map
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Cycle: 2016
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 3/31/2016 4:32:05 PM
Updated: 11/21/2016 1:17:20 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

High

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 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 remain assessed (monitored) as “not supported” (IR 5p) due to violations of Iowa water quality criteria for indicator bacteria. The Class B(WW2) aquatic life uses remain “not assessed” (IR 3a) due to the lack of water quality information upon which to base an assessment. The source of data for this assessment remains the results of monitoring in 2010 at Stations WQ-06 and WQ-12 of the Catfish Creek Watershed Project (quality assurance/project plan available upon request).

Assessment Explanation

The presumptive Class A1 (primary contact recreation) uses remain assessed as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric mean of indicator bacteria (E. coli) in the 11 samples collected approximately every two weeks during the recreational season of 2010 at Site WQ-06 of the Catfish Creek Watershed Project (1,496 orgs/100 ml) far exceeded the Iowa water quality criterion to protect primary contact recreation uses (126 orgs/100 ml). Nine of the 11 samples (82%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. Similarly, at Station WQ-12, the geometric mean of E. coli in the 11 samples collected (5,714 orgs/100 ml) also far exceeded the Class A1 geometric mean criterion. All 11 samples exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).

Monitoring and Methods

Assessment Key Dates

5/12/2010

Fixed Monitoring Start Date

10/27/2010

Fixed Monitoring End Date

Methods

420

Indicator bacteria monitoring