Unnamed Tributary to Dry Run IA 02-CED-6294

from mouth (T89N R14W Sec23 Black Hawk Co.) to headwaters (T89N R14W Sec9 Black Hawk 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: 8/17/2016 10:05:48 AM
Updated: 9/29/2016 10:40:11 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

Special project/study

TMDL Priority

Tier III

Class BWW1

Presumptive Use

Aquatic Life - Warm Water Type 1

Fully Supported

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 (monitored) as "partially supported” due to levels of indicator bacteria that exceed state water quality criteria. The presumptive Class B(WW1) aquatic life uses are assessed (monitored) as “fully supported” based on data collected from 2013 through 2014. The source of data for this assessment is the results of (1) chemical and physical monitoring conducted from April 2013 through November 2014 at Site DRC-6D1 at Cedar Falls (STORET station 11070008) and (2) results of bacteria monitoring at this station from August 2012 through October 2014.

Assessment Explanation

[Note: Monitoring site DRC-6D1 is located Dry Run Creek and is used to assess segment IA 02-CED-0390_0; thus, this assessment may be in error: station DRC-6D1 may not be in this segment.]

The presumptive Class A1 (primary contact recreation) are assessed (monitored) as "partially supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2012 through 2014 at Section 319 Site DRC-6D1 were as follows: the 2012 geometric mean was 218 orgs/100 ml, the 2013 geometric mean was 616 orgs/100 ml, and the 2014 geometric mean was 262 orgs/100 ml. All three geometric means exceeded the Class A1 criterion of 126 orgs/100 ml. Eleven of the 24 samples (46%) exceeded the Class A1 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 a recreation season geometric mean exceeds the respective water quality criterion, the contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “impaired.”

The presumptive Class B(WW1) aquatic life uses are assessed (monitored) as “fully supported” based on results of chemical/physical monitoring conducted for the Dry Run Creek Watershed project in 2013 and 2014. No violations of Class B(WW1) criteria for dissolved oxygen (19 samples), temperature (19 samples), pH (18 samples), or chloride (17 samples) occurred during the 2013-2014 monitoring period. These results suggest “full support” of the presumptive Class B(WW1) aquatic life uses.

Monitoring and Methods

Assessment Key Dates

8/27/2012

Fixed Monitoring Start Date

10/28/2014

Fixed Monitoring End Date

Methods

240

Non-fixed station physical/chemical (conventional + toxicants)

420

Indicator bacteria monitoring