Does EPA have a validation protocol that should be followed when modifying a method or evaluating a proposed modification?
In general, SW-846 is considered guidance with the exception of Methods Defined Parameters (MDPs). SW-846 does not have to be used for analyzing waste under RCRA unless the regulation requires a specific method for analyses and compliance. A list of the required MDPs can be found in 40 CFR Part 260.11.
ORCR does allow “appropriate modifications”. However, the responsibility is on the laboratory to demonstrate the applicability and appropriateness of all modifications. It has always been ORCR’s policy to recommend that the analyst document any/all changes and seek approval from their regulated authority (e.g., Region or State) before initiating modification to any methods, as stated in SW-846. By seeking approval, the analyst has a documented and approved change, if granted, in their Quality Assurance Project Plan or Sampling Analysis Plan. Several ORCR Federal Register notices have explained this. See: The Methods Innovation Rule (MIR) (70FR34538, June 14, 2005, page 34543-44) and Update V of SW-846 (78 FR, No. 205, October 23, 2013, page 63189).
Guidance on submitting new methods for RCRA can be found at: www.epa.gov/hw-sw846/sw-846-method-development. However, we do not have specific guidance for methods modifications unless the user is seeking “equivalency”. There is a process to petition the EPA Administrator to seek equivalency for a method, although the RCRA program does not follow these guidelines. Guidance on the Equivalency Petition process can be found in 40 CFR §260.21, and more information can be found at www.epa.gov/dwanalyticalmethods/drinking-water-alternate-test-procedure-program and www2.epa.gov/cwa-methods/alternate-test-procedures. In addition, there are other methods that may be appropriate in addressing what the lab is trying to accomplish.
When a lab proposes a modification to a non-MDP method under the flexibility clause, its scope should be limited to the type of sample for which they have demonstrated performance, and not apply to all samples. If they offer demonstrated performance on a wider variety of samples, then the applicability of the modification can be expanded.
The lab's regulatory authority has the power to approve or disapprove a given modification if it believes the lab has failed to demonstrate adequate performance, and appropriateness for a given application, sample matrix, or site. It may be relatively easy to demonstrate performance for a given type of sample, but it is very difficult to demonstrate adequate performance for all sample types. In the same manner, we have not validated a method for all sample types. However, some USGS or ASTM methods may be appropriate, although we have not included them in SW-846. Science has a wide range, and having an approved, appropriate, well documented study will always reduce ambiguity and have greater credibility in court.