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Why we regulate
Learn what types of wastewater discharges are regulated and how
Plan review
The DNR reviews plans for municipal and industrial wastewater treatment plant construction
Discharge permits
Wastewater discharges to surface or groundwaters
Contact information
For information contact:
Kari Fleming
Biomonitoring Coordinator
Environmental Toxicologist
(608) 267-7663

Making WET limits and monitoring decisions

Using the WET Checklist

Chapter 1.3 of the WET Guidance Document (PDF, 1.3MB) describes the steps that Department staff should take as they review WET data and make decisions on the need for WET monitoring and limits. In that chapter, the WET limits and monitoring determination process has been broken down into three steps: 1) collecting and summarizing data, 2) selecting representative data, and 3) determining the monitoring frequency and the need for limits by completing the WET Checklist. The following is a brief summary of the guidance found in Chapter 1.3. For more details, users should consult Chapter 1.3 of the WET Guidance Document.

Step 1 - Data Collection and summarization

At the time of WET evaluation, all available WET data should be collected and summarized. WET data with firm documentation of data quality problems should be eliminated from the data set at this stage in the process. A quick call to the Department's Biomonitoring Coordinator, the permittee, or the WET lab that generated the data could make identification of suspect data easier.

Step 2 - Selecting representative data

It is important to remember that all data are not automatically representative of the discharge being evaluated. Efforts should be made to insure that decisions about monitoring and limits are made based on data that is representative of the discharge being evaluated. If it is determined that representative data are not available, the Department usually relies on WET monitoring and is not bound to setting WET limits in the permit. When there is doubt regarding the representativeness of one or a few data points, additional WET data may clarify the representativeness of those data. When representativeness of existing data is questionable, more experienced permittees will learn to conduct additional tests when faced with positive results that they know may trigger a limit or more frequent monitoring.

Step 3 - Determination of monitoring frequency and need for a limit using the WET Checklist

Once it has been determined which data are representative, Department staff must decide whether a WET limit is necessary and how much monitoring should be done. The WDNR establishes WET limits "to insure that substances shall not be present in amounts which are harmful to aquatic life..." (see NR 106.08, Wis. Adm. Code). WET limits should be given when data shows a toxicity problem may exist. WET and facility-specific data should be assessed and the checklist redone with each permit reissuance.

Whole Effluent Toxicity (WET) Checklist

To help Department staff make limit and monitoring decisions, the Biomonitoring Team created the "Whole Effluent Toxicity (WET) Checklist", which is described briefly below. The checklist is designed to assist staff when assigning WET limits and levels of WET monitoring to individual discharges, based on their potential to exhibit toxicity and/or exceed water quality standards. The higher the potential for toxicity is determined to be, the more points a discharge accumulates. As points accumulate, more monitoring is recommended to insure that toxicity is not occurring.

The WET Checklist is designed to assist staff when making decisions regarding WET monitoring and limits to be placed into a permit. It is intended solely as guidance and recommendations based on the checklist should be made accordingly. If staff have reason to believe that more or less WET monitoring is necessary than that recommended by the checklist, they can choose to put more or less monitoring into the permit.

NOTICE: The WET Guidance Document and WET Checklist are intended solely as guidance, and do not contain any mandatory requirements except where requirements found in statute or administrative rule are referenced. This guidance does not establish or affect legal rights or obligations, and is not finally determinative of any of the issues addressed. This guidance does not create any rights enforceable by any party in litigation with the State of Wisconsin or the Department of Natural Resources. Any regulatory decisions made by the Department of Natural Resources in any matter addressed by this guidance will be made by applying the governing statutes and administrative rules to the relevant facts.

The Biomonitoring Team has designed an electronic version of the checklist and it is available for Department staff use. A "WET Checklist Questions Summary" is given below. This summary includes questions asked, information needed, and points assessed in the WET checklist. This summary is intended as a guide for use when determining what information will be needed to complete the electronic version of the WET Checklist or for sharing completed checklist information with others. The summary is not intended for use in place of the electronic version available to Department staff.

The Checklist assigns points based on the number of factors present which increase the chances for effluent toxicity. Points are based on the responses given to questions included in Attachment 3 (PDF, 1.3MB) of Chapter 1.3. For each question, points are assessed towards acute, chronic, or both types of monitoring. The completed checklist recommends necessary acute and chronic limits and monitoring frequencies, based on points accumulated.

For more information and directions for completing the WET Checklist, see Chapter 1.3 of the WET Guidance Document (PDF, 1.3MB).

Last revised: Wednesday October 16 2013