Rock Creek IA 02-CED-586

from confluence with unnamed tributary (NW 1/4 SE 1/4 S17 T97N R17W Mitchell Co.) confluence with Goose Cr. in S35 T98N R18W Mitchell 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
View assessment methodology in new window

Cycle: 2020
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 9/1/2020 12:13:14 PM
Updated: 10/16/2020 9:42:13 AM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5p - Impairment occurs on a waterbody with a presumptive A1 or B(WW1) use.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2016

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Special project/study

TMDL Priority

Tier III

Class BWW1

Aquatic Life - Warm Water Type 1

WINOFI

Biological: low aquatic macroinvertebrate IBI

Support Level

Further Investigation Needed

Impairment Code

3b-c - Use potentially biologically impaired based on calibrated IBI metrics.

Cause Magnitude

Moderate

Status

New

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2020

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

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 presumptive Class A1 use was assessed as “not supported” due to violations of water quality criteria for indicator bacteria (E. coli). The Class BWW1 use was assessed as "partially supported" based on biological sampling data. All other designated uses were "not assessed".

Assessment Explanation

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
CEDARMIT	21	WQ	CY 2016-2017	14000132	Rock Creek	Near Foothill Ave (2D)
Iowa DNR	6	BIO	See Below	57	Rock Creek	Rock Creek

Presumptive Class A1 - Indicator Bacteria:

Site ID	Data Source ID	# Samples / # Years	2016 Geometric Mean	2017 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
14000132	21	12 / 2	512	1144	Yes	12	100%	Yes	Monitored	Not

Presumptive 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
14000132	21	12 / 2	8.3	8.1	8.1	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
14000132	21	Dissolved oxygen	8 / 2	11.7	7.5	6.6	NA / 0	NA / 0%	No	Evaluated	Full
14000132	21	pH	12 / 2	8.3	8.1	8.1	0 / NA	0% / NA	No	Monitored	Full
14000132	21	Temperature	12 / 2	23.3	15.5	15.7	0 / 0	0% / 0%	No	Monitored	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
57	8/8/17	46	47c	MS/WW	Hess	40	Fair	70	Fail
57	8/20/13	46	47c	MS/WW	Hess	68	Good	70	Fail

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	Riffle Stream?	FIBI score	FIBI Class	47c FIBI BIT	FIBI Pass/ Fail
57	8/8/17	46	47c	MS/WW	Yes	71	Excellent	65	Pass
57	8/20/13	46	47c	MS/WW	Yes	80	Excellent	65	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	Earned IR Category	Actual IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (0/2)	Partial
Fish	Evaluated	Pass (2/2)	Full
Overall	Evaluated	Fail	Partial	3bc	3bc	Assessment is evaluated because it used samples collected not in the last five years.

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

8/21/2002

Biological Monitoring

9/10/2009

Biological Monitoring

8/20/2013

Biological Monitoring

6/23/2016

Non-fixed Monitoring Start Date

10/17/2017

Non-fixed Monitoring End Date

Methods

150

Monitoring data more than 5 years old

220

Non-fixed station physical/chemical monitoring (conventional pollutant only)

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys

420

Indicator bacteria monitoring