South Raccoon River IA 04-RAC-1181

mouth (S21 T78 R27W Dallas Co.) to confluence with Middle Raccoon R. in S9 T78N R29W near Redfield in Dallas 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
View assessment methodology in new window

Cycle: 2018
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 5/29/2019 11:00:00 AM
Updated: 7/8/2019 3:03:50 PM

Use Support

Class A1

Recreation - Primary contact

Partially Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Partially Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

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 BWW1

Aquatic Life - Warm Water Type 1

Fully Supported

Class HH

Human Health -

Not Assessed

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" due to levels of indicator bacteria that violate state water quality criteria. The Class B(WW1) aquatic life are assessed (monitored) as "fully supported” based on results of ambient chemical/physical water quality monitoring from 2014 through 2016 and on 2012/2013/2015 DNR/SHL biological sampling. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this river segment. The source of data for this assessment are the results of (2) DNR/SHL ambient monthly monitoring during the 2014-2016 assessment period at STORET ambient monitoring station 10250001 (formerly station 429340) located near Redfield approximately 1 mile downriver from the confluence of Middle Raccoon and South Raccoon rivers and (2) 2012/2013/2015 DNR/SHL biological sampling conducted near Redfield.

Assessment Explanation

The Class A1 (primary contact recreation) uses are assessed (monitored) as "not 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 2014 through 2016 at STORET ambient monitoring station 10250001 were as follows: the 2014 geometric mean was 1921 orgs/100 ml, the 2015 geometric mean was 352 orgs/100 ml, and the 2016 geometric mean was 598 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Seventeen of the combined 24 samples (71%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and DNR’s assessment/listing methodology, if the geometric mean is greater than 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). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as "not supported."

This evaluated biological assessment was based on data collected in 2012, 2013 and 2015 as part of the DNR/SHL large river sampling project. A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa collected in the stream sampling reach. The biological metrics were combined to make a benthic macroinvertebrate index (BMIBI). The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2012 BMIBI scores were 53 (fair) and 59 (good). The 2013 BMIBI scores were 43 (fair) and 57 (good).The 2015 BMIBI score was 52 (fair).The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of biological data collected at stream ecoregion reference sites from 1994-2008. The BMIBI BIC for this ecoregion is 51. This assessment is considered evaluated because the drainage area (988 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria. Even though this site passed the BMIBI BIC (4/5), it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the site used for the assessment doesn’t fall in the calibrated watershed size.

Results of chemical/physical water quality monitoring at STORET ambient monitoring station 10250001 also suggest “full support” of the aquatic life uses. Monitoring showedno violations of Class B(WW1) water quality criteria for 35 Ammonia samples (maximum = 0.1 mg/L), 36 Dissolved Oxygen samples (minimum = 7.5 mg/L), 35 pH samples (range = 7.2 to 8.7), 36 Temperature samples (maximum = 25.9° c), 36 Chloride samples (maximum = 22 mg/L), or 36 Sulfate samples (maximum = 43 mg/L) occurred during monitoring from January 2014 to December 2016.According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), the EPA guidelines allow up to 10% violations of these conventional parameters before impairment of water quality is indicated. Thus, these results thus suggest “full support” of the Class B(WW1) aquatic life uses.

Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this stream segment.

Monitoring and Methods

Assessment Key Dates

8/8/2012

Biological Monitoring

9/6/2013

Biological Monitoring

1/9/2014

Fixed Monitoring Start Date

12/8/2016

Fixed Monitoring End Date

10/8/2015

Biological Monitoring

Methods

230

Fixed station physical/chemical (conventional plus toxic pollutants)

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

420

Indicator bacteria monitoring