Iowa DNR

Water Quality Assessments

Impaired Waters List

Hewitt Creek IA 01-NMQ-109

mouth (S29/30 T89N R2W Dubuque Co.) to confluence with Hickory Cr. in S21 T89N R2W Dubuque Co.

Assessment Cycle
Release Status
Release Period
2016 - 2018
6/10/2020 9:03:21 AM
Overall IR Category
4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Last Updated
2/17/2021 11:05:40 AM
Assessments conducted in accordance with Iowa's Integrated Report methodology.
Use Support
Class A1
Primary contact
Not Assessed
Class BWW2
Aquatic Life
Warm Water Type 2
Partially Supported
Fish Kill: Caused By Animal Waste
Impairment Code
4d - Pollutant-caused fish kill. No TMDL needed and administrative action taken against responsible party.
Cause Magnitude
Agriculture: Feedlots
Source Confidence
Cycle Added
Impairment Rationale
Pollutant-caused fish kill
Data Source
Fish kill investigation: Iowa DNR
General Use
General Use water
Not Assessed
Impairment Delistings
No delistings for this assessment cycle.
Assessment Summary

The Class BWW2 aquatic life use was assessed as “partially supported” based on a 2017 fish kill investigation. All other designated uses were "not assessed".

Assessment Explanation

Class BWW2 - Fish kill Assessment:

The Class BWW2 aquatic life use assessment based on the 2017 fish kill placed this segment in Category 4d. The fish kill was caused by a “pollutant” or was suspected to be caused by a “pollutant”; therefore, the Class BWW2 use was considered impaired. However, because restitution for the fish killed was received, the Class BWW2 use was placed in Category 4d (impaired but TMDL not required). DNR feels that (1) TMDLs should not be required for a fish kill caused by a one-time illegal or unauthorized release of a pollutant where enforcement action was taken and (2) enforcement action is more appropriate and effective for addressing a spill-related impairment than the TMDL process.

Details about the 2017 fish kill can be found here:

Monitoring and Methods
Assessment Key Dates
10/9/2017 Fish Kill
120 Surveys of fish and game biologists/other professionals
140 Incidence of spills and/or fish kills
330 Fish surveys