Shell Rock River IA 02-SHL-783

from south corporate limit of Shell Rock (S12 T91N R15W Butler Co.) to confluence with Flood Cr. in S27 T93N R16W Butler Co.

Assessment Cycle

2020

Release Status

Final

Data Collection Period

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.

Overall IR Category: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown

Created: 9/4/2020 10:13:52 AM
Updated: 10/14/2020 1:38:49 PM

Assessment conducted in accordance with Iowa's 2020 IR methodology

Use Support

Class A1

Recreation

Primary contact

Presumptive Use

Partially Supported

Impairments

Support Level

Partially Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2018

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

Partially Supported

Impairments

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

2012

Impairment Rationale

Fish consumption advisory in effect: no more than 1 meal/week

Data Source

Fish contaminant monitoring: Iowa DNR

TMDL Priority

Tier IV

General Use

General Use water

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed as "partially supported" based on levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The Class BWW1 use was assessed as "fully supported" based on biological sampling data and water quality monitoring data. The Class HH use remains assessed as "partially supported" based on fish tissue sampling data and due to the existence of a one meal per week fish consumption advisory for mercury.

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 2016-2018	10120001	Shell Rock River at Shell Rock
Iowa DNR	6	BIO	See Below	843	Shell Rock River	Shell Rock
Iowa DNR	6	FT	See Below	68	Shell Rock River W of Clarksville	Shell Rock

Class A1 - Indicator Bacteria:

Site ID	Data Source ID	# Samples / # Years	2016 Geometric Mean	2017 Geometric Mean	2018 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
10120001	6	22 / 3	129.04	81.8	263	Yes	6	27%	Yes	Monitored	Partial

Class A1 - pH:

Site ID	Data Source ID	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
10120001	6	36 / 3	9.3	8.2	8.2	1	3%	No	Monitored	Full

Class BWW1 - Conventional Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	% Acute/ Chronic Violations	Significantly >10% Violations	Assessment Type	Support Level
10120001	6	Ammonia	36 / 3	0.77	0.06	0.02	0 / 0	0% / 0%	No	Monitored	Full
10120001	6	Chloride	36 / 3	29	19.5	19	0 / 0	0% / 0%	No	Monitored	Full
10120001	6	Dissolved oxygen	36 / 3	14.5	11	11	NA / 0	NA / 0%	No	Monitored	Full
10120001	6	pH	36 / 3	9.3	8.2	8.2	1 / NA	3% / NA	No	Monitored	Full
10120001	6	Sulfate	36 / 3	56	31	27	0 / NA	0% / NA	No	Monitored	Full
10120001	6	Temperature	36 / 3	23.8	11.2	10.6	0 / 0	0% / 0%	No	Monitored	Full

Class BWW1 - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	% Acute/ Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
10120001	6	Aluminum	9 / 2	0.85	0.32	0.28	0 / 0	0% / 0%	No	Evaluated	Full
10120001	6	Arsenic	9 / 2	2	1.34	1.2	0 / 0	0% / 0%	No	Evaluated	Full
10120001	6	Cadmium	9 / 2	0.025	0.025	0.025	0 / 0	0% / 0%	No	Evaluated	Full
10120001	6	Chromium	9 / 2	1.2	0.88	0.88	0 / 0	0% / 0%	No	Evaluated	Full
10120001	6	Copper	9 / 2	2.4	0.85	0.7	0 / 0	0% / 0%	No	Evaluated	Full
10120001	6	Lead	9 / 2	0.09	0.051	0.06	0 / 0	0% / 0%	No	Evaluated	Full
10120001	6	Nickel	9 / 2	3.1	2.4	2.4	0 / 0	0% / 0%	No	Evaluated	Full
10120001	6	Selenium	9 / 2	2.1	1.32	1.3	0 / 0	0% / 0%	No	Evaluated	Full
10120001	6	Zinc	9 / 2	2.6	1.48	1.2	0 / 0	0% / 0%	No	Evaluated	Full

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/ Thermal	BM Sample Gear	BMIBI score	BMIBI Class	47c BMIBI BIT	BMIBI Pass/ Fail
843	8/15/16	1730	47c	MS/WW	Hess	81	Excellent	70	Pass
843	9/8/14	1730	47c	MS/WW	Float ArtSub	65	Good	52	Pass
843	9/8/14	1730	47c	MS/WW	Hess	65	Good	70	Fail

Overall Assessment:

Community	Assessment Type	Assessment Result	Support Level	Earned IR Category	Actual IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Pass (2/3)	Full	1	1	Assessment is evaluated because the drainage area of the sample site is larger than calibrated range.

Class HH – Fish Tissue Sampling:

Site ID

Date

Species Name

Biopart

# in sample

chlordane result

chlordane violation (>0.6)?

PCBs result

PCBs violation (>0.2)?

Hg result

Hg violation (>0.3)?

Assessment Type

Support Level

8/2/2012

walleye

plug

0.285

Evaluated

Full

8/23/2011

walleye

plug

0.753

Yes

Evaluated

Partial

8/23/2011

common carp

fillet

<0.03

<0.09

0.206

Evaluated

Full

Follow-up monitoring was conducted in 2012 to better define the level of mercury in Shell Rock River fish and to provide information for any changes needed to the consumption advisory. Results showed that the average level of mercury in tissue samples from three Walleye was just below the consumption advisory threshold of 0.3 ppm (ave = 0.285, sd = 0.078).

A one meal/week consumption advisory for mercury exists on this segment of the Shell Rock River – seeIowa Consumption Advisories

Because a one meal per week fish consumption advisory covers this waterbody, the fish consumption uses are assessed as “partially supported.”

Class HH-F - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	Number of Non - Detects	Mean Value > Criterion or MCL	Assessment Type	Support Level
10120001	6	Cadmium	9 / 2	0.025	0.025	0.025	9	No	All Non-Detect	Full
10120001	6	Chromium	9 / 2	1.2	0.88	0.88	0	No	Evaluated	Full
10120001	6	Copper	9 / 2	2.4	0.85	0.7	0	No	Evaluated	Full
10120001	6	Nickel	9 / 2	3.1	2.4	2.4	0	No	Evaluated	Full
10120001	6	Selenium	9 / 2	2.1	1.32	1.3	0	No	Evaluated	Full
10120001	6	Zinc	9 / 2	2.6	1.48	1.2	0	No	Evaluated	Full

Monitoring and Methods

Assessment Key Dates

8/23/2011

Fish Tissue Monitoring

8/25/2016

Biological Monitoring

1/7/2016

Fixed Monitoring Start Date

12/11/2018

Fixed Monitoring End Date

8/2/2012

Fish Tissue Monitoring

9/8/2014

Biological Monitoring

Methods

230

Fixed station physical/chemical (conventional plus toxic pollutants)

260

Fish tissue analysis

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

420

Indicator bacteria monitoring