US  EPA has published its final decision on its reconsideration of the methods used by NPDES permittees to test for Oil & Grease. In the 2010 proposed Methods Update Rule (MUR), EPA discussed a new method, ASTM D7575, for oil and grease. The agency subsequently published a Notice of Data Availability (NODA) on this method that provided new data and requested comment on whether and how EPA should approve the method in Part 136 as an alternative oil and grease method.

As background, EPA establishes test procedures in 40 CFR Part 136. When EPA has promulgated a test procedure for analysis of a specific pollutant, an NPDES permittee must use an approved test procedure for the specific pollutant  However, 40 CFR Part 136 also recognizes that new technologies and approaches are constantly being developed, including methods for pollutants for which EPA already has an approved test procedure. The CWA allows for use of an alternate method for a specific pollutant or parameter that is different from the approved test procedure (i.e., limited use approval). Requests for such uses, along with supporting data, are made to the applicable Regional Alternate Test Procedure (ATP) Coordinator for consideration and approval.

Unlike many parameters, oil and grease is not a unique chemical entity, but is a mixture of chemical species that varies from source to source. Common substances that may contribute to oil and grease include petroleum based compounds such as fuels, motor oil, lubricating oil, soaps, waxes, and hydraulic oil and vegetable based compounds such as cooking oil and other fats. Currently, Part 136 lists EPA Method 1664A  for the measurement of oil and grease

In 2010, EPA proposed to add new and revised EPA methods to its Part 136 test procedures. Among other methods, EPA described, but did not approve, three oil and grease methods, ASTM D7575, ASTM D7066 and Standard Methods 5520.  Because EPA expressed interest in the use of solvent-free methods, EPA evaluated the ASTM D7575 method for the measurement of oil and grease and announced it was re-considering its decision not to include ASTM D7575 in 40 CFR Part 136 as an alternative to EPA Method 1664A for measuring oil and grease.

After consideration, EPA concluded that ASTM D7575 is a good stand alone method for the measurement of oil and grease. However, EPA also concluded that the case has not yet been made that ASTM D7575 should be approved for nationwide use as an alternative oil and grease method. However, EPA considered various approaches for allowing its use as an alternative to approved methods. EPA has concluded such determinations should be made on a case by case basis rather than a nationwide basis.

EPAs approach to approve ASTM D7575 as an alternative oil and grease method requires permittees to demonstrate comparability (side-by-side data) to the permitting authority. To determine comparability for a specific application, with approval of the ATP Coordinator, a permittee could use the specific side by side comparison procedures. Under this approach, a permittee would only be able to use ASTM D7575 if the recommended procedures demonstrated comparability.

EPA anticipates that requests for the use of ASTM D7575 as an alternative oil and grease method could be widespread, and wants to ensure that such requests are handled consistently. EPA recommends that applicants demonstrate comparability by conducting a side-by-side comparison using the specific procedures recommended in the guidance document that was developed when Method 1664A was promulgated. Comparability could be shown if this side by side comparison demonstrates there is no significant difference between the promulgated method and ASTM D7575. EPA notes that such requests may provide sufficient additional data to allow EPA at a later date to later make a nationwide determination on the approval of ASTM D7575 as an alternative oil and grease method.

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