2020 Final assessment for Cedar Creek

Cedar Creek IA 03-SKU-905

mouth (S9 T71N R7W Henry Co.) to confluence with Little Cedar Cr. in S17 T70N R7W Henry 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: 9/9/2020 12:59:25 PM
Updated: 10/16/2020 10:37:47 AM

Assessment conducted in accordance with Iowa's 2020 IR methodology

Use Support

Class A1

Partially Supported

Bacteria: Indicator Bacteria- E. coli

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

2008

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier III

Class BWW1

WINOFI

Organic Enrichment: Low Dissolved Oxygen

Support Level

Water in Need of Further Investigation (WINOFI)

Impairment Code

3b - Use potentially impaired based on an evaluated assessment.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2016

Impairment Rationale

Significantly > 10% of samples fail to meet criterion

Data Source

Ambient monitoring: Iowa DNR-continuous

Temperature: Thermal Modifications

Support Level

Water in Need of Further Investigation (WINOFI)

Impairment Code

3b - Use potentially impaired based on an evaluated assessment.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2016

Impairment Rationale

Significantly > 10% of samples fail to meet criterion

Data Source

Ambient monitoring: Iowa DNR-continuous

Class HH

Fully Supported

General Use

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed as "partially supported" due to levels of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW1 use remains assessed as "partially supported" based on continuous DO and temperature monitoring data. The Class HH use was assessed as “fully supported” based on water quality monitoring data.

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	10440001	Cedar Creek near Oakland Mills
Iowa DNR	6	BIO	See Below	194	Big Cedar Creek	Gibson Rec Area -Oakland Mills

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
10440001	6	23 / 3	247.98	182.86	81.62	Yes	9	39%	Yes	Monitored	Partial

Class A - pH:

Site ID	Data Source ID	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
10440001	6	36 / 3	8.6	8.1	8.2	0	0%	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
10440001	6	Ammonia	36 / 3	0.48	0.07	0.02	0 / 0	0% / 0%	No	Monitored	Full
10440001	6	Chloride	36 / 3	72	31.7	29.5	0 / 0	0% / 0%	No	Monitored	Full
10440001	6	Dissolved oxygen	36 / 3	15.2	10.5	10	NA / 0	NA / 0%	No	Monitored	Full
10440001	6	pH	36 / 3	8.6	8.1	8.2	0 / NA	0% / NA	No	Monitored	Full
10440001	6	Sulfate	36 / 3	210	73	62	0 / NA	0% / NA	No	Monitored	Full
10440001	6	Temperature	36 / 3	31.8	13.8	11.6	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
10440001	6	Aluminum	9 / 2	6.4	1.021	0.36	0 / 0	0% / 0%	No	Evaluated	Full
10440001	6	Arsenic	9 / 2	3.2	1.68	1.6	0 / 0	0% / 0%	No	Evaluated	Full
10440001	6	Cadmium	9 / 2	0.07	0.03	0.025	0 / 0	0% / 0%	No	Evaluated	Full
10440001	6	Chromium	9 / 2	1.3	0.77	0.68	0 / 0	0% / 0%	No	Evaluated	Full
10440001	6	Copper	9 / 2	3.5	2	2	0 / 0	0% / 0%	No	Evaluated	Full
10440001	6	Lead	9 / 2	0.44	0.131	0.1	0 / 0	0% / 0%	No	Evaluated	Full
10440001	6	Nickel	9 / 2	5.5	3.6	3.4	0 / 0	0% / 0%	No	Evaluated	Full
10440001	6	Selenium	9 / 2	2.6	1.24	1.1	0 / 0	0% / 0%	No	Evaluated	Full
10440001	6	Zinc	9 / 2	2.2	1.32	1.3	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	40a BMIBI BIT	BMIBI Pass/ Fail
194	8/13/18	533	40a	MS/WW	Hess	56	Good	41	Pass
194	10/4/16	533	40a	MS/WW	Hess	57	Good	41	Pass
194	10/4/16	533	40a	MS/WW	Float ArtSub	39	Fair	41	Fail
194	9/6/16	533	40a	MS/WW	Hess	57	Good	41	Pass
194	9/6/16	533	40a	MS/WW	Float ArtSub	57	Good	41	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	Earned IR Category	Actual IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Pass (4/5)	Full	1	1	Assessment is evaluated because it the drainage area of the sample site was larger than the calibrated range.

Class BWW1 – Continuous Monitoring:

Results of continuous monitoring of dissolved oxygen (DO) and temperature conducted in 2012 at the DNR station 10440001 near Oakland Mills suggest “partial support” of the Class BWW1 aquatic life use. The lowest DO concentration recorded in 29 days of continuous monitoring was 2.8 mg/L. The daily DO minimum concentration failed to meet the 24-hour DO criterion (5 mg/L) in 15 of 29 days. The percentage exceeding (51.7%) was greater than (failing) the 10% impairment threshold used to assess conventional water quality parameters. The associated statistical analysis confidence level test was high (>90%). The 16-hour DO criterion (5 mg/L) was exceeded in 8 of 29 days. The percentage exceeding (27.6%) was greater than (failing) the 10% threshold with high statistical confidence (>90%). The maximum stream temperature recorded during the sensor deployment period was 34.5 degrees (C). The temperature criterion for warmwater interior streams (32 C) was exceeded in 9 of 29 days. The percentage exceeding (31%) was greater than (failing) the 10% impairment threshold with high statistical confidence (>90%). Due to violations of the 16-hour DO criterion and stream temperature criterion, the BWW1 aquatic life use is assessed as impaired for DO and temperature. The assessment type is “evaluated” because they are based on data collected from a single year within the current data assessment period. In order to meet the requirements for a “monitored” assessment, the DNR’s continuous monitoring assessment methodology requires monitoring data from two or more years within the assessment period.

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
10440001	6	Cadmium	9 / 2	0.07	0.03	0.025	8	No	Evaluated	Full
10440001	6	Chromium	9 / 2	1.3	0.77	0.68	0	No	Evaluated	Full
10440001	6	Copper	9 / 2	3.5	2	2	0	No	Evaluated	Full
10440001	6	Nickel	9 / 2	5.5	3.6	3.4	0	No	Evaluated	Full
10440001	6	Selenium	9 / 2	2.6	1.24	1.1	0	No	Evaluated	Full
10440001	6	Zinc	9 / 2	2.2	1.32	1.3	0	No	Evaluated	Full

Monitoring and Methods

Assessment Key Dates

9/6/2016	Biological Monitoring
10/4/2016	Biological Monitoring
1/6/2016	Fixed Monitoring Start Date
12/10/2018	Fixed Monitoring End Date
7/3/2012	Non-fixed Monitoring Start Date
7/31/2012	Non-fixed Monitoring End Date
8/13/2018	Biological Monitoring

Methods

150	Monitoring data more than 5 years old
222	Non-fixed-station monitoring (conventional during key seasons and flows)
230	Fixed station physical/chemical (conventional plus toxic pollutants)
315	Regional reference site approach
320	Benthic macroinvertebrate surveys
420	Indicator bacteria monitoring

Water Quality Assessments

Impaired Waters List

Cedar Creek IA 03-SKU-905

Assessment Summary

Assessment Explanation

Assessment Key Dates

Methods