Clean Water Act Analytical Methods

Alternate Test Procedures

""The Clean Water Act Alternate Test Procedure (ATP) program is described at 40 CFR 136.4 and 136.5. This program provides a mechanism for submission and review of an application for nationwide use or limited use of an ATP for measurement of a pollutant as an alternative to the methods approved at 40 CFR Part 136. An ATP may fall into one of two categories:
  1. A method using a determinative technique (e.g., a pollutant detector) different from that in an existing Part 136 method (for method validation and evaluation purposes this type of method is referred to as a new method), or
  2. A modification to a Part 136 method that falls outside the scope of the modification flexibility described in the Part 136 method, or at 40 CFR 136.6 (for validation and evaluation purposes this type of method is referred to as an ATP).
A method developer may apply for review of a method modification or a new method through the ATP program.

How to Submit an ATP Application

EPA has provided detailed guidance about the kind of information it needs to evaluate methods for potential approval. The Agency conducts a notice-and-comment rulemaking process for methods evaluated under the ATP program, before they are incorporated into the Part 136 regulations. The types of information required for an application are described in three protocol documents: two for chemical methods, and one for microbiological methods.

EPA updated the protocols in 2016 for the review of ATPs and new methods for chemical analytes. EPA welcomes comments or suggestions for improvement or clarification of the protocols. Please direct any comments or suggestions to Lemuel Walker ( Use the phrase “Protocol Comments” in the subject line of any email.
Note: EPA does not have an ATP review protocol for toxicity testing under EPA's Whole Effluent Toxicity (WET) program.

Before submitting a method to EPA for an ATP review, a developer confers with EPA to design a method validation study. This study tests the new or modified method in several representative matrices and independent laboratories. The method also must also be written in a standard format that includes all of the steps in an approved method, such as sample and data handling, and quality assurance requirements.

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Flexibility to Modify Methods - 40 CFR 136.6

If you use a modification to an approved 40 CFR Part 136 method and document the modification as described at 40 CFR 136.6, you will no longer receive or require a letter from EPA. The March 12, 2007 Methods Update Rule that promulgated § 136.6, as modified by the May 18, 2012 Methods Update Rule allows the regulated community more flexibility to modify approved methods without EPA review, provided certain requirements are met.
This regulation allows the analytical community greater flexibility to modify approved methods to lower the costs of measurements, overcome matrix interferences, or otherwise improve the analysis without EPA review. Laboratories that modify Part 136 methods may be private, public or commercial and may conduct analyses for one or more clients or facilities.

Related Information

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Additional Information

For additional information, please contact Lemuel Walker ( or call 202-566-1077.