Shell Rock River IA 02-SHL-786

from confluence with the Winnebago River (Floyd Co.) to confluence with Rose Cr. in NW 1/4 S8 T97N R18W Cerro Gordo 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 2016 - 2018
Stream/River Water Quality Data	CY 2016 - 2018
Lake Water Quality Data	CY 2014 - 2018
Biological Sampling Data	CY 2014 - 2018*
Fish Kill Data	CY 2014 - 2018
Fish Tissue Sampling Data	CY 2014 - 2018
Continuous Dissolved Oxygen Sampling Data	CY 2014 - 2018
*Biological sites sampled in both 2013 and 2017 were also assessed.

Open Segment Map
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Cycle: 2020
Release Status: Final
Overall IR: 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Trend: Unknown
Created: 9/4/2020 10:33:56 AM
Updated: 10/15/2020 12:15:50 PM

Use Support

Class A1

Recreation - Primary contact

Partially Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Partially Supported

Impairment Code

4a - Pollutant-caused impairment. TMDL has been completed.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2006

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: USGS

Class BWW1

Aquatic Life - Warm Water Type 1

WINOFI

Biological: low fish IBI

Support Level

Further Investigation Needed

Impairment Code

3b-u - Use potentially biologically impaired based on uncalibrated IBI metrics.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2016

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR Fisheries

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 use remains assessed as “partially supported” based on levels of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW1 use was assessed as "partially supported" based on biological sampling data. All other designated uses were "not assessed". Note: A TMDL for indicator bacteria in this segment of the Shell Rock River was approved by EPA in February 2010; therefore, the Class A1 primary contact recreation use impairment was moved from IR Category 5a to IR Category 4a.

Assessment Explanation

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2002-2004	11340001	Shell Rock River at Rockford	68
Iowa DNR	6	BIO	See Below	1032	Shell Rock River	Rockford Impoundment – SH005
Iowa DNR	6	BIO	See Below	1033	Shell Rock River	Rockford below dam – SH006
Iowa DNR	6	BIO	See Below	1034	Shell Rock River	Nagle Wildlife Area – SH007

Class A1 - Indicator Bacteria:

Site ID	Data Source ID	# Samples / # Years	2002-2004 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
11340001	6	23 / 3	72	No	5	22%	Yes	Evaluated	Partial

Class BWW1 - Biological Sampling:

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	Riffle Stream?	FIBI score	FIBI Class	47c FIBI BIT	FIBI Pass/ Fail
1034	8/15/18	517	47c	MS/WW	Und	74	Excellent	44	Pass
1032	8/14/18	529	47c	MS/WW	Und	57	Good	44	Pass
1033	8/14/18	531	47c	MS/WW	Und	71	Excellent	44	Pass
1034	7/26/17	517	47c	MS/WW	Und	43	Fair	44	Fail
1032	7/25/17	529	47c	MS/WW	Und	39	Fair	44	Fail
1033	7/25/17	531	47c	MS/WW	Und	41	Fair	44	Fail
1032	7/22/15	529	47c	MS/WW	Und	39	Fair	44	Fail
1033	7/22/15	531	47c	MS/WW	Und	38	Fair	44	Fail
1034	7/21/15	517	47c	MS/WW	Und	43	Fair	44	Fail
1034	7/23/14	517	47c	MS/WW	Und	40	Fair	44	Fail
1032	7/22/14	529	47c	MS/WW	Und	37	Fair	44	Fail
1033	7/22/14	531	47c	MS/WW	Und	21	Poor	44	Fail

Overall Assessment:

Community	Assessment Type	Assessment Result	Support Level	Earned IR Category	Actual IR Category	Reason
Fish	Evaluated	Fail (3/12)	Partial	3bu	3bu	Assessment is evaluated because the drainage areas of the sample sites are larger than the calibrated range.

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

1/8/2002

Fixed Monitoring Start Date

12/8/2004

Fixed Monitoring End Date

7/23/2014

Biological Monitoring

7/22/2014

Biological Monitoring

7/21/2015

Biological Monitoring

7/22/2015

Biological Monitoring

7/25/2017

Biological Monitoring

7/26/2017

Biological Monitoring

8/14/2018

Biological Monitoring

6/1/2016

Fixed Monitoring Start Date

2/1/2010

TMDL Completed

Methods

150

Monitoring data more than 5 years old

315

Regional reference site approach

330

Fish surveys

420

Indicator bacteria monitoring