Beaver Creek IA 04-UDM-1233

mouth (S17 T79N R24W Polk Co.) to the Polk/Dallas county line (west line S18 T80N R25W Polk Co.

Assessment Cycle

2022

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 2018 - 2020
Stream/River Water Quality Data	CY 2018 - 2020
Lake Water Quality Data	CY 2016 - 2020
Biological Sampling Data	CY 2016 - 2020*
Fish Kill Data	CY 2016 - 2020
Fish Tissue Sampling Data	CY 2016 - 2020
Continuous Dissolved Oxygen Sampling Data	CY 2016 - 2020
*Biological sites sampled in both 2015 and 2019 were also assessed.

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

Created: 12/27/2021 11:08:47 AM
Updated: 12/27/2021 11:10:06 AM

Assessment conducted in accordance with Iowa's 2022 IR methodology

Use Support

Class A1

Recreation

Primary contact

Presumptive Use

Not Supported

Impairments

Support Level

Not Supported

Impairment Code

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

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 BWW2

Aquatic Life

Warm Water Type 2

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 use was assessed as "not supported" due to levels of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW2 use was assessed as "fully supported" based on biological sampling data and water quality monitoring data.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2018-2020	10770001	Beaver Creek near Grimes
Iowa DNR	6	BIO	See Below	910	Beaver Creek	Grimes

Presumptive Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2018/ 2019/2020)

2018 Geometric Mean

2019 Geometric Mean

2020 Geometric Mean

Violates Annual Geometric Mean?

# 2018 SSM violations / SSM Violations needed for impairment

# 2019 SSM violations / SSM Violations needed for impairment

# 2020 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

10770001

8/7/8

1465

333

592

YES

7 / 3

5 / 3

6 / 3

YES

Monitored

Not

Class A - pH

Site ID	Data Source ID	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
10770001	6	36 / 3	7.5	8.7	8.1	0	7	NO	Monitored	Full

Class BWW2 - Conventional Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	# Acute / Chronic Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
10770001	6	Ammonia	36 / 3	0.025	1.3	0.1	NA	0 / 1	7	NO	Monitored	Full
10770001	6	Chloride	36 / 3	16	96	34	NA	0 / 0	7	NO	Monitored	Full
10770001	6	Dissolved Oxygen	36 / 3	7.3	16.3	10.5	0	NA / NA	7	NO	Monitored	Full
10770001	6	pH	36 / 3	7.5	8.7	8.1	0	NA / NA	7	NO	Monitored	Full
10770001	6	Sulfate	36 / 3	12	180	47	0	NA / NA	7	NO	Monitored	Full
10770001	6	Temperature	36 / 3	0	28.1	12.7	0	NA / NA	7	NO	Monitored	Full

Class BWW2 - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
10770001	6	Aluminum	14 / 3	5.9	1.1	0.3	0 / 0	NO	Monitored	Full
10770001	6	Arsenic	13 / 3	2.8	1.8	1.5	0 / 0	NO	Monitored	Full
10770001	6	Cadmium	13 / 3	0.28	0.06	0.02	0 / 0	NO	Monitored	Full
10770001	6	Chromium	13 / 3	3.2	1.1	1.1	0 / 0	NO	Monitored	Full
10770001	6	Lead	13 / 3	0.24	0.13	0.11	0 / 0	NO	Monitored	Full
10770001	6	Nickel	13 / 3	4.5	3.2	3.3	0 / 0	NO	Monitored	Full
10770001	6	Silver	13 / 3	0.025	0.025	0.025	0 / 0	NO	Monitored	Full
10770001	6	Zinc	13 / 3	5.5	2.3	1.9	0 / 0	NO	Monitored	Full

Class BWW2 - Biological Sampling:

Benthic Macroinvertebrates:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	47b BMIBI BIT	BMIBI Pass/Fail
910	7/17/19	358	47b	MS	Floating Art Sub	72	Good	62	Pass
910	8/31/16	358	47b	MS	Floating Art Sub	67	Good	62	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Monitored	Pass (2/2)	Full		Assessment is monitored because samples used to complete the
Overall	Monitored	Pass	Full	1	assessment were collected in the last five years.

Monitoring and Methods

Assessment Key Dates

1/3/2018

Fixed Monitoring Start Date

12/8/2020

Fixed Monitoring End Date

7/17/2019

Biological Monitoring

8/31/2016

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