South River IA 04-LDM-1074

mouth (Warren Co.) to confluence with Squaw Cr. in S2 T75N R24W Warren 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: 10/18/2016 4:11:27 PM
Updated: 10/18/2016 4:11:27 PM

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

Moderate

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 (primary contact recreation) uses are assessed (monitored) as "partially supported" (IR 5p) due to levels of indicator bacteria that violate state water quality criteria. The Class B(WW2) aquatic life are assessed (monitored) as "fully supported” (IR 2a) based on results of physical/chemical monitoring. The source of data for this assessment is the results of IDNR/SHL ambient monthly monitoring during the 2012-2014 assessment period at STORET station 10910003 (formerly station 426046) at the Highway 92 bridge near Ackworth.

Assessment Explanation

The presumptive Class A1 uses are assessed (monitored) as "partially supported" based on results of ambient monitoring for indicator bacteria (E. coli). The geometric means of indicator bacteria (E. coli) in the 25 samples collected during the recreational seasons of 2012 through 2014 at IDNR station 10910003 near Ackworth were as follows: the 2012 geometric mean was 440 orgs/100 ml, the 2013 geometric mean was 269 orgs/100 ml, and the 2014 geometric mean was 596 orgs/100 ml. All three geometric means exceed the Class A1 criterion of 126 orgs/100 ml. Thirteen of the 25 samples (52%) 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 Class B(WW2) aquatic life uses are assessed (monitored) as "fully supported”. None of the approximately 36 samples collected during the 2012-2014 assessment period at the IDNR/SHL monthly station violated Class B(WW2) water quality criteria for pH, temperature, ammonia-nitrogen, chloride, or sulfate. One of the 36 samples (3%) had a level of dissolved oxygen (3.2 mg/l) that violated the Class B(WW2) criterion of 5.0 mg/l. According to U.S. EPA guidelines for Section 305(b) reporting (U.S. EPA 1997b: page 3-17), a violation frequency for conventional parameters such as dissolved oxygen of less than 10% does not suggest an impairment of aquatic life uses. Thus, the results of chemical/physical water quality monitoring from 2012-2014 suggest “full support” of the Class B(WW2) aquatic life uses.

Monitoring and Methods

Assessment Key Dates

1/4/2012

Fixed Monitoring Start Date

12/3/2014

Fixed Monitoring End Date

Methods

230

Fixed station physical/chemical (conventional plus toxic pollutants)

420

Indicator bacteria monitoring