Wisconsin Department of Natural Resources


Frequently Asked Questions (FAQ)

The answers to the following FAQs are kept brief here, due to space limitations. Each of these issues is addressed in more detail in The WET Guidance Document and/or The Methods Manual (PDF, 545KB). References to specific sections of these documents have been added to each FAQ, as appropriate.

Do you have an FAQ or a question regarding WET tests or biomonitoring? If so, contact the WDNR's Biomonitoring Coordinator, Kari Fleming.

NOTICE: The WET Guidance Document and these FAQs 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.

What are WET tests?

In whole effluent toxicity (WET) tests, lab-reared aquatic organisms are exposed to various dilutions of effluent for a specific time period, in order to predict at what levels the effluent may cause harm to the organisms (e.g., at what level death, reproductive impairment, or growth inhibition occurs).

Test treatments consist of a series of solutions containing different proportions of an effluent sample. A control treatment (an exposure of organisms to dilution water with no effluent added) is used to provide a measure of the acceptability of the test by indicating the quality of the test organisms and the suitability of the dilution water, test conditions, and handling procedures. At the end of the test, the performance (e.g., survival, growth, or reproduction) of the effluent treatments is compared to the performance of the controls to determine whether the effluent had a significant impact on the test organisms.

For more information regarding WET testing procedures and requirements, see the The Methods Manual (PDF, 545KB).

How long does it take to complete a WET test?

There are typically two types of WET tests. Acute tests last 48 to 96-h. The objective of an acute test is to determine at what concentration the effluent may produce a harmful effect during a short-term exposure under controlled conditions. Because death is an easily detected harmful response, the measured effect for acute tests is lethality

The second type of WET tests are chronic tests. Chronic tests predict the concentrations that interfere with normal growth, development, and reproductive potential of aquatic organisms. During chronic tests, several life stages of the organism are continuously exposed to the test material at various concentrations. Chronic tests required by the WDNR last about 7 days. The response measured for fathead minnows is growth and survival; for C. dubia it is reproduction and survival. The C. dubia test encompasses the entire life cycle of the organism and therefore the most sensitive stages. The fathead minnow test, which uses fish less than 1 day old, seeks to also use the most sensitive life stage of the organism. For more details, see The Methods Manual (PDF, 545KB).

What organisms are used in WET tests?

Species used for WET tests must be sensitive to toxic substances, necessary for the overall health of the food chain, and representative of the indigenous population present in the possible area of impact of the test material. These so called "indicator organisms" are used to estimate what may be happening in the environment when the effluent is introduced. All of the species required by the WDNR have been used in toxicity tests for many years.

The species Ceriodaphnia dubia belongs to a group of freshwater microcrustaceans, and may be referred to as water fleas, zooplankton, cladocerans, or daphnids. These invertebrates are a major component of the freshwater zooplankton and are the dominant planktivorous (algae-eating) herbivores in lakes. They are abundant in ponds, quiescent sections of streams and rivers, and lakes throughout North America. The selection of C. dubia for routine use in toxicity testing is appropriate for a number of reasons, including: 1) they are broadly distributed and present throughout a wide range of habitats, 2) they are an important link in aquatic food chains and a significant source of food for small fish, 3) they have a short life cycle and are easy to culture in the laboratory, 4) they are sensitive to a broad range of contaminants, and 5) their small size requires small volumes of test water, leading to ease in sampling and transportation of wastewater samples.

Fathead minnows (Pimephales promelas) belong to the family Cyprinidae (the family which includes carps and minnows), the dominant freshwater family in terms of number of species. The fathead minnow is native to much of North America and thrives in ponds, lakes, ditches, and streams. Fathead minnows are good laboratory fish, taking readily to that life and adapting well to the dry commercial fish food, brine shrimp, etc., that is necessary for laboratory culturing.

Selenastrum capricornutum is a freshwater green algae and is representative of higher order vascular plants. It is NOT a blue-green algae (which we usually associate with algae blooms and nuisance conditions). Like the other species used in WET tests, S. capricornutum was chosen because of its importance in the food chain and its ability to represent other species in its trophic level. Like the other species, the selection of S. capricornutum for routine use in toxicity testing is appropriate for a number of reasons, including: 1) They are broadly distributed and present throughout a wide range of habitats (i.e., they are abundant in ponds, streams, rivers, and lakes throughout North America), 2) they are an important link in aquatic food chains and are a significant source of food for higher organisms (e.g., zooplankton, fish, etc.), 3) they have a short life cycle and are easy to culture in the laboratory, 4) they are sensitive to a broad range of contaminants, and 5) their small size requires small volumes of test water, leading to ease in sampling and transportation of wastewater samples.

Why do we need to do WET tests?

When limits were first written into WPDES permits, they were based on physical factors such as biological oxygen demand (BOD) and suspended solids. Later, additional components were added, such as the 126 "priority pollutants". Water quality criteria were then used to calculate effluent limits for these pollutants, where possible. However, water quality criteria, and therefore effluent limits, exist for only a few of the thousands of chemicals in use today. Another mechanism is needed to predict the effects of chemicals which do not have water quality criteria.

Like many other states and the USEPA, Wisconsin uses an integrated approach for controlling toxic pollutants that uses WET testing to complement chemical-specific analyses as a means to protect aquatic life. The use of WET testing is necessary in addition to chemical-specific testing, due to several factors, including: 1) the limitations of chemical-specific analysis methods (e.g., chemical-specific lab analyses may not be sensitive enough to determine if a water quality criteria is being met), 2) inadequate chemical-specific aquatic toxicity data (i.e., not enough data to calculate chemical-specific water quality criteria), and 3) the inability of chemial-specific criteria to predict the toxicity of chemicals when combined in an effluent.

Since the promulgation of chs. NR 105 and NR 106, Wis. Adm. Code, WET testing has become a major part of the Department's water pollution control program. All surface water dischargers are evaluated using The WET Checklist to determine if WET testing should be included in their WPDES permit.

How much do WET tests cost?

Due to the labor associated with the culturing and maintenance of organisms and the length of testing, WET tests are relatively expensive when compared to some chemical-specific or permit related tests. However, the market for these tests is becoming increasingly competitive and costs have dropped dramatically over the years. When asked by the biomonitoring team during the summer of 1995, laboratories estimated test costs as follows: acute tests = @ $500.00 each; chronic tests @ $1000.00 - $1500.00 each. This made a combined acute/chronic test battery cost as much as $2000.00.

Cost estimates for these same tests in 1997-1999 showed that costs had fallen at some labs to:

Acute tests

$200.00 - $300.00 each *

Chronic tests

$600.00 - $1500.00 each ($900.00 average) #

Combined acute/chronic

approx. $800.00 - $1800.00. #

* based on a 1997 estimate
# based on a DNR survey of certified WET labs, conducted in 1999

Remember, these are only estimates! Costs depend on the specifics of each test (e.g., number of dilutions, species, replicates, etc.), the lab you choose, and are not necessarily the same in all situations.

How do I tell one lab from another in terms of quality?

All WET tests conducted for compliance with a WPDES permit must be conducted by a laboratory certified or registered by the WDNR (according to NR 149.22, Wis. Adm. Code). Today there are 5 laboratories certified by the WDNR and one permittee lab that is registered to do their own testing. For a list of the certified labs available to do WET tests for hire, see Certified WET Labs . In order to become certified, a lab must pass an on-site audit conducted by the WDNR's Bureau of Integrated Science Services. Due to their small number, the Biomonitoring Coordinator is able to keep in close contact with the labs conducting WET tests. If you have questions or concerns about the quality of a WET laboratory, you can contact the WDNR's Biomonitoring Coordinator, Kari Fleming. To receive a copy of a lab's latest audit report, permittees can contact the Bureau of Integrated Science Services at (608) 267-7633. For more information regarding how to choose a WET testing laboratory, see Chapter 2.1 of The WET Guidance Document.

What do test results mean?

Acute WET tests estimate the "end of pipe" conditions, or the effect of the effluent without any dilution considerations. Acute test results are usually reported as an "LC50" (the "Lethal Concentration", or % effluent which causes 50% of the organisms to die). If greater than 50% of the organisms die in 100% effluent, the test is "positive" and it is determined that the effluent has the potential to cause harm to aquatic life in the receiving water.

LC50s are statistical analyses used to estimate the lethality of a sample in WET acute tests. In order to calculate an LC50, at least one of the test concentrations must cause more than 50% mortality. The lower the LC50, the more toxic the effluent. For example, an LC50 > 100% means that full strength effluent did not kill 50% of the test organisms. An LC50 = 50% means that half strength effluent killed 50% of the test organisms.

Chronic WET tests estimate the effects of the effluent after it has mixed with the receiving water. An "IC25" is used to estimate the effects on growth or reproduction of a sample in WET chronic tests. The IC25 value is compared to the instream waste concentration (IWC) for the facility. The IC25 is an estimate of the effluent "Inhibition Concentration" which causes a 25% reduction in growth or reproduction of the test organisms. If the IC25 is lower than the IWC, the effluent has the potential to impact the organisms in the receiving water.

For more information regarding LC50s and IC25s, see Chapter 2.4 of The WET Guidance Document.

How common are WET test failures?

Data from the WDNR database in 1998 showed that industrial facilities are a little more likely to fail acute WET tests than are municipal facilities. Data collected from 1989-1997 showed that 25% of the municipalities that performed acute tests failed at least one. On an individual test basis, municipalities failed 65 of 520 tests, or about 12.5% of the time. On the other hand, data from 1989-1997 showed that 50% of the industries that performed acute tests failed at least one. Industrial facilities failed 140 of 847 total acute tests performed, or 16.5% of the time.

Data also shows that industrial facilities are a little more likely to fail chronic WET tests. Data from 1989-1997 showed that 23% of the municipalities that performed chronic tests failed at least one. On an individual test basis, municipalities failed 53 of 373 tests, or about 14% of the time. This same time period showed that 42% of the industries that performed chronic tests failed at least one. Industrial facilities failed 83 of 493 total tests performed, or 17% of the time.

What is my regulatory liability with failed tests?

Many WPDES permits contain language requiring WET monitoring to be conducted and providing specific follow up actions in the event of a test failure. Typically, two follow up tests must be performed within 60 days of the failure. Inclusion of such language in a permit does not constitute an effluent limitation and thus an effluent violation does not occur with a test failure. In certain instances such as repeated test failures, inability or unwillingness to address toxicity issues, and/or a clear potential for impact to the receiving water fish and aquatic life community, a WET effluent limitation may be included in the permit. WET limits are expressed in "Toxic Units (TU)" in WPDES permits as "1.0 TUa" (acute) or "1.0 rTUc" (chronic). Basically, once a WET limit appears in a premit, any WET test failure is a permit violation.

Since WET limitations are usually implemented in situations that indicate a high likelihood that the effluent is toxic or where sensitive conditions exist, WET limit violations are taken very seriously by the Department. The test itself is intended to measure the direct potential for impairment of fish and aquatic life communities related to substances present in effluents at toxic concentrations. Thus, any failure of a WET effluent limitation should be considered serious and appropriate action taken.

For more information, see Chapter 1.8 (Enforcement of WET Limits), Chapter 2.2 (Toxicity Reduction Evaluations), or Chapter 2.4 (Toxic Units) of The WET Guidance Document.

What do I do if I fail?

In most cases, permits only require WET monitoring. Then, in the event of a test failure, two follow up tests must be performed within 60-90 days. Since this language in a permit does not constitute an effluent limitation, an effluent violation does not occur with a test failure. Therefore, in these situations, only the two retests are required. If the two retests are "passes", this may indicate that the original failure was caused by a one-time or infrequent event. This, by itself, does not usually cause the Biomonitoring Team significant concern.

However, the Biomonitoring Team recommends that a permittee start investigating as soon as the effluent has shown the potential for persistent toxicity, instead of waiting for the WDNR to take action. What is meant by an effluent "showing the potential for persistent toxicity"? This means situations where a facility has experienced severe or repeated failures in a series of tests. When a group of tests such as an original test followed by two retests have produced toxic results, it is an indication that a persistent toxicity problem exists in the effluent being tested. These positive results are cause for concern.

When an effluent has shown potential for severe or persistent toxicity, the WDNR has the authority to modify the permit to include additional WET monitoring, compliance schedules for WET limits, and/or Toxicity Reduction Evaluations (TRE), since the potential for exceedance of water quality criteria exists. The Biomonitoring Team prefers to allow permittees to investigate on their own in order to attempt to identify the cause of toxicity, without modifying the permit. In this way, the Biomonitoring Team and the permittee can attempt to fix the problem and avoid the complications and time restrictions brought about when TREs are placed in permits. For more information, see Chapter 2.2 (Toxicity Reduction Evaluations) of The WET Guidance Document.

What is involved in a TRE? (How much do they cost? How long do they take? How successful are they?)

A toxicity reduction evaluation (TRE) is an investigation completed by the permittee, intended to determine those actions necessary to remove toxicity. The TRE may identify a solution as simple as improved housekeeping procedures or require a more extensive investigation to identify cost-effective treatment or source reduction options.

  • STEP 1: One of the first steps of a TRE is the collection of data and facility-specific information. This step is used to define TRE study objectives, identify what is already known, and possibly provide clues as to the causes and sources of toxicity. This information may suggest immediate actions which may be useful in reducing effluent toxicity.
  • STEP 2: The next step of the TRE process involves optimization of facility operations in order to try to reduce effluent toxicity. Three areas are usually investigated during this step: 1) facility housekeeping, 2) treatment plant operation, and 3) the selection and use of process and treatment chemicals.
  • STEP 3: The next step is where most of the costs of a TRE are incurred, when a laboratory conducts a toxicity identification evaluation (TIE). The objective of the TIE is to characterize and identify the actual cause(s) of toxicity through a series of effluent manipulations and toxicity tests. The evaluation can use both characterization procedures and chemical-specific analyses, therefore, the identifications may range from generic classes of toxicants (e.g., metals, organics, etc.) to specific chemical compounds. Multiple samples are needed for TIEs and one objective of the TIE is to determine if and how toxicity varies over time.
  • STEP 4: Once the TIE step has been completed, the TRE process can go in two directions. One approach is to evaluate options for treating the final effluent, the other is to identify the source(s) of toxicity and then evaluate upstream treatment options, process modifications, product substitutions, or source reduction. A decision can be made to pursue both approaches, and then to select the most technically and economically attractive option.

Because of the differences between operations and complexity of facilities and in the differences between characteristics and variability of effluents, flexibility in the design of TRE studies is essential and approaches used are often facility specific. Because of the facility-specific nature of these studies, it is also hard to estimate the time associated or the costs. The laboratory work involved in the TIE portion of the study is often the most expensive part of the TRE. Past studies which have been most successful have been very well organized, and much work was often done up front to try to narrow the scope of the project (i.e., in the data collection, facility optimization steps). The TIE step involves a series of effluent manipulations at the lab, where the manipulations that are successful give you a clue about the family and characteristics of the toxicant(s) you are looking for. The TREs that often are the most costly and time consuming (often seeming to never really find the problem) are those that are missing the up front work. With the correct data collection and treatment plant knowledge, it may be possible to narrow the focus of the TIE to a few chemical families, rather than the entire universe of chemicals. However, one must be careful not to jump to conclusions, for if too many steps are skipped, the one that would have given the right answers may be eliminated.

For guidance on how to start a TRE, see Chapter 2.2 of the WET Guidance Document. For a list of labs that have performed TREs, see WET Labs With Experience Performing Successful Toxicity Reduction Evaluations

What can I do to get WET testing out of my permit?

The WDNR determines the amount of WET monitoring needed by individual discharges, based on their potential to exhibit effluent toxicity, using The WET Checklist. The more factors present which have the potential to impact a discharge's toxicity potential, the more monitoring is necessary to insure that toxicity is not occurring. In order to make attempts to reduce the amount of monitoring recommended for their discharge, permittees need to know what may influence their effluent's toxicity potential, so adjustments can be made where possible.

Factors which the Biomonitoring Team has included in their guidance for determining a discharge's toxicity potential include, but are not limited to: 1) Instream Waste Concentration (IWC), 2) WET data history & Reasonable Potential Factors (RPF) (facility-specific WET data is used to calculate an RPF. "Reasonable potential" is defined as where an effluent "is projected or calculated to cause an excursion above a water quality standard". When reasonable potential exists, effluent limits are given), 3) compliance history and the effects of WWTP loading, production variability, WWTP upsets, and WWTP operations on effluent variability, 4) stream classification, 5) chemical-specific effluent data, 6) additives, 7) discharge category and contributors, 8) WW treatment, and 9) ecological impacts. For more information regarding WET limits and monitoring requirements, see Chapter 1.3 of The WET Guidance Document (Representative Data, Reasonable Potential & Monitoring Frequencies).

Some possible steps that permittees can take to reduce their toxicity potential may include:

  • conduct additional testing and/or TREs if toxicity problems have occurred (e.g., reduction/elimination of toxic sources may make old data nonrepresentative, additional "passes" may make past "failures" have less impact, etc.),
  • investigate what operational adjustments could be made that could reduce toxicity, such as increasing aeration basin detention time, sludge age, etc.,
  • maintain or strive for compliance with other limits,
  • make efforts toward reducing or improving reaction time to WWTP upsets,
  • improve WWTP practices which may effect effluent variability or toxicity (e.g., improve facility housekeeping practices),
  • make efforts to remove/reduce toxic discharges (e.g., pollution prevention activities, selection and use of process and treatment chemicals, etc.), and
  • communicate with industrial contributors and educate them about the implications of their actions.

What does the DNR do with receiving water data (collected during WET tests)?

The WDNR requires most permittees to use the receiving water upstream of the discharge as the diluent in WET tests (i.e., effluent is mixed with receiving water to make up test concentrations). In order to insure that only effluent effects are measured in these tests and that receiving water effects do not interfere with test results, certain criteria have been established to keep track of receiving water performance. These criteria are very stringent (e.g., acute receiving water controls are only allowed 10% mortality, as opposed to the 50% mortality an effluent is allowed to "pass") and therefore a receiving water that does not meet one of these criteria is not necessarily "toxic". In most cases, natural factors can be found which explain why a receiving water did not perform perfectly in a WET test.

However, in order to insure that receiving water samples that have shown repeated control problems are not indicative of potential toxicity problems in the receiving water, the Biomonitoring Team maintains an "ambient biomonitoring network" with the UW-Madison State Laboratory of Hygiene's Biomonitoring Lab (exit DNR) (SLH). Through this project, WDNR staff select sites where toxicity problems may be present and the SLH performs toxicity tests and identification studies in an attempt to reduce or eliminate the problem.

In 1996, the Biomonitoring Team and SLH developed a toxicity screening test for use with DNR "basin teams". This new tool provides a quick estimate of potential toxicity problems, while requiring less time and effort on the part of WDNR staff (which means many more sites can be tested). With this new screening tool, basin teams can screen effluents and receiving waters for potential toxicity problems and set priorities within the watershed and evaluate the effectiveness of their actions.

Do I have to keep using receiving water as a diluent after a control failure?

Following a test where the receiving water has not met test acceptability criteria, the permittee should evaluate the situation to see if there are any obvious factors which may be contributing to the poor performance of the receiving water (e.g., if the sample was taken near another discharge, a dam or other physical structure, or another potentially toxic source). The receiving water control results, subsequent sampling evaluation, and change in sampling location (if applicable) should be noted in the test report or accompanying cover letter. If the permittee does identify a possible contaminating source, it will be necessary for the permittee to change the location of their receiving water sampling.

If the receiving water has performed poorly in repeated tests and no obvious cause or contributing factor can be found, subsequent tests of the discharge may be completed using laboratory water as the primary control water and diluent. A receiving water control should be set in conjunction with the test, as the secondary control, so receiving water performance can be monitored. The permittee or lab should call the biomonitoring coordinator to get approval for switching to the use of lab water. This change and the approval should then be noted by the permittee or lab on the WET report form.

If after subsequent tests, receiving water problems appear to have diminished, the biomonitoring coordinator may again ask that the receiving water be used as the diluent. Acceptable laboratory control water can be synthetic (reconstituted) or natural uncontaminated ground or surface waters collected from another source. When laboratory water is used as the primary test control or diluent water source, hardness (as CaCO3) must be adjusted as required in the Methods Manual (Section 4.4).

For more information regarding dilution waters used in WET tests see Chapter 2.7 of The WET Guidance Document (Invalid RW Controls).

Can improper sampling techniques cause WET failures?

It is very important that sampling equipment is cleaned appropriately, in order to insure that samples are representative of the effluent and no confounding factors are present (i.e. to remove any possible contamination). If the facility sampler or a portable sampler is used, the tubing should be replaced with new tubing, including the pump head tubing. If this is not possible, all tubing should be cleaned and rinsed according to Section 1 of the Methods Manual. Artifactual toxicity may occur when sampling equipment is not cleaned regularly. Microorganisms can colonize surfaces that are in contact with the effluent. Some of these microbes can produce endotoxins that are toxic to the test organisms. Before sampling, you should replace all of the tubing and clean any parts that contact the sample.

It is also important that a representative sample be obtained under "normal" operating conditions unless there is a specific reason to collect a sample during an atypical situation. Collection of samples for WET testing will usually consist of either two or three separate 24 hour composites samples. Samples should be chilled during collection, through the use of a refrigeration unit or a cooler with at least twenty pounds of ice. During hot weather or when collecting very warm effluents, it may be necessary to add more ice before the end of the sample period.

Disconnection of tubing or power supplies is probably the single most common cause for missed samples. All tubing and cords should be secured to surrounding structure to prevent accidental disconnections. Frozen sample lines can also occur in winter if using a composite sampler. You should consider minimizing the risk of freezing by selecting a protected site for the sampler, repositioning the tubing, or decreasing the intervals between sampling. If possible, select a site that is indoors.

Section 2 of the Methods Manual requires samples to be rejected by the laboratory if the sample arrives at the laboratory over the < 36 hour holding time or if they are warmer than 10oC (unless the amount of time elapsed from the end of collection is < 4 h). If samples are rejected, tests may have to be restarted and/or repeated, at the cost of the permittee. Courier services will usually guarantee delivery within certain time periods, with the purchase of additional shipping insurance. Shipping insurance may cost from $5 - $30 per sample, but may prevent costs associated with test restarts or repeats. Sample containers should be placed in a cooler and packed with ice. If the sample is shipped via commercial carrier, you should seal the sample and ice within a large plastic bag, as the carrier may return the sample if it leaks in transit.

For more information regarding sample handling and acceptability requirements, see Section 1 of The Methods Manual (PDF, 545KB) and Chapter 1.1 of The WET Guidance Document.

Is test variability unusually high in WET tests?

Comparisons of WET method precision with method precision for other analytes commonly limited in WPDES permits clearly demonstrate that the variability of the WET methods is within the range of variability experienced in other types of analyses. Several independent researchers and studies also have concluded that method performance improves when prescribed methods are followed closely by experienced analysts. Factors which can affect WET test variability, precision, and success include: the experience and skill of the laboratory analyst; test organism age, condition, and sensitivity; dilution water quality; temperature control; and the quality and quantity of food provided.

The issue of WET variability has been discussed by a variety of groups in many different forums. Chapter 2.9 of The WET Guidance Document discusses WET variability and ways to control it in more detail. Other guidance has also been written by other groups such as the Society of Toxicology and Chemistry (SETAC) "Expert Advisory Panel on WET Test Performance and Data Interpretation" (see http://www.setac.org (exit DNR)).

WET variability can basically be categorized into 3 types:

  • Intratest (within-test) variability. Sources of intratest variability include the number of replicates, the number of organisms per replicate, and the sensitivity differences between organisms.
  • Intralab (within-lab) variability. Intralab variability is that which is measured when tests are conducted under reasonably constant conditions in the same lab. Sources of intralab variability include those sources described for intratest variability, plus differences in: 1) test conditions (e.g., seasonal differences in dilution water & environmental conditions), 2) organism condition/health, and 3) analyst performance.
  • Interlab (between-lab) variability. Interlab variability reflects the degree of precision that is measured when a sample is analyzed by multiple labs using the same methods. Variability measured between labs is a consequence of variability associated with both intratest and intralab variability factors, plus differences allowed within the test methods, technician training programs, sample and organism culturing/shipping effects, testing protocols, and testing facilities.

WET Variability can be controlled in a number of ways, including: 1) Strict adherence to clearly specified methods, 2) Increasing analyst & regulator experience, and 3) Using quality labs. Wisconsin has addressed these issues in an attempt to reduce WET variability.

In order to control WET variability and improve the consistency of methods used by Wisconsin labs and permittees, the WDNR created the "State of Wisconsin Aquatic Life Toxicity Testing Methods Manual in 1996. The Methods Manual contains specific procedures regarding testing and sampling procedures, types of tests, quality control/quality assurance procedures, etc., that labs must follow when performing WET tests for permit compliance. The WET Guidance Document also provides guidance regarding issues that may effect test variability (e.g., sampling procedures, selecting a quality lab, etc.).

In order to insure labs are of the highest quality and are able to demonstrate a serious commitment to a quality assurance/control program, the WDNR, under state statutes, certifies labs to perform different types of environmental analysis. In order for a lab to apply for certification for acute and chronic WET testing, the lab must submit a completed application and a quality assurance plan to the lab certification program and pass an on-site evaluation. WET labs must have an ongoing reference toxicant program, a review process for all test data and reporting, a good sample custody system, proper equipment maintenance, dilution water quality monitoring, facility maintenance, and attention to test organism health, and make other demonstrations of good lab practices in order to pass an audit.

For more information, contact: Kari Fleming