Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Montgomery Creek IA 03-SSK-6508

from mouth (SE1/4 NE1/4 S35 T85N R25W Boone Co.) to headwaters (NW1/4 S22 ST85N R26W Boone Co.)

Cycle
2024
Release Status
Final
Overall IR
5 - Water is impaired or threatened and a TMDL is needed.
Trend
Unknown
Created
11/1/2023 8:13:38 AM
Updated
2/1/2024 9:05:44 AM
Use Support
Class A1
Recreation - Primary contact
Not Supported
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
2014
Impairment Rationale
Geometric mean criterion exceeded
Data Source
Volunteer monitoring
TMDL Priority
Tier III
Class BWW1
Aquatic Life - Warm Water Type 1
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 exceeded state water quality criteria. The presumptive Class BWW1 use was assessed as “fully supported” based on biological sampling 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 2008-2012

908020

Montgomery Creek

Site SC-11

Iowa DNR

6

BIO

See Below

873

Montgomery Creek

Gilbert


Presumptive Class A1 - Indicator Bacteria: 2008-2012

Site ID

Data Source ID

# Samples / # Years

2008-2012 Geometric Mean

Annual Geometric Mean Violation

# Violations

% Violations

Significantly >10% Violations

Assessment Type

Support Level

908020

6

10 / 5

465

Yes

7

70%

Yes

Evaluated

Not


Presumptive Class BWW1 - Biological Sampling:


Benthic Macroinvertebrates:

BioNet Site ID

Date

Drainage Area (mi2)

Ecoregion

Major Drainage/Thermal

BM Sample Gear

BMIBI score

BMIBI Class

47b BMIBI BIT

BMIBI Pass/Fail

873

8/9/13

16

47b

MS/WW

Hess

66

Good

62

Pass


Fish:

BioNet Site ID

Date

Drainage Area (mi2)

Ecoregion

Major Drainage/Thermal

Riffle Stream?

FIBI score

FIBI Class

47b FIBI BIT

FIBI Pass/Fail

873

8/9/13

16

47b

MS/WW

Yes

50

Fair

53

Pass*


Overall:

Community

Assessment Type

Assessment Result

Support Level

IR Category

Reason

Benthic Macroinvertebrates

Evaluated

Pass (1/1)

Full

*FIBI score passed when 7 pt. UAV was applied to the single sample.

Fish

Evaluated

Pass (1/1)

Full

Assessment was evaluated because the drainage area of

Overall

Evaluated

Pass

Full

1

the sample site was smaller than the calibrated range.

Monitoring and Methods
Assessment Key Dates
5/10/2008
Monitoring Start
10/13/2012
Monitoring End
8/9/2013
Biological Monitoring
Methods
150
Monitoring data more than 5 years old
315
Regional reference site approach
320
Benthic macroinvertebrate surveys
330
Fish surveys
420
Indicator bacteria monitoring