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Water: CWA Methods

Approved Methods

Questions and Answers


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When do I need to use an approved 40 CFR Part 136 method?

You need to use an approved 40 CFR Part 136 method when your permit or permitting authority requires it.


When do know I am using an approved method?

If your method is specified in your permit or in the regulations at CFR Part 136.3 and Parts 401-503. These approved methods also include modifications to the method that are within the method flexibility discussed at 40 CFR Part 136.6.


Are all CWA compliance methods listed in 40 CFR Part 136?

Most CWA compliance methods are listed in 40 CFR Part 136, but your permitting authority or permit may specify use of other methods.


May I use EPA Office of Resource Conservation and Reclamation's SW846 methods?

Generally, no, for wastewater measurements. The permittee is required to use approved CWA methods for compliance purposes. SW846 methods are not necessarily developed for the same monitoring purposes or matrices for which CWA methods are developed. However, your permitting authority may allow use of SW846 or other methods in sewage sludge (biosolids).

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What may we do when the EPA approved CWA method does not work for my discharge or CWA application?

For chemical methods, you may demonstrate that there is interference and implement corrective action as described in Solutions to Analytical Chemistry Problems with Clean Water Act Methods (PDF) (62 pp, 458K). For microbial methods, you may submit a limited use ATP application to your permitting authority (e.g., State or EPA Region).

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Are there approved methods for sewage sludge (biosolids)?

EPA has approved the following microbial methods for use in biosolids: EPA Method 1680 and 1681 for fecal coliforms and EPA Method 1682 for Salmonella.

40 CFR Part 136 chemical methods are not approved specifically for use in biosolids. However, the following EPA methods have been used:

Other methods may be available in Solid Waste Methods.

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What methods are available for fish tissue?

The Office of Water has used the following EPA methods for chemicals in fish tissue:

There are other methods that may be available in Solid Waste Methods.

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Where is the site listing of approved methods for air and radiation, solid waste, drinking and waste water, pesticides and toxic substances, etc.?

EPA's Forum on Environmental Measurement

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