December 8, 1992

Dear Ms. Sharatz:

This is in response to your November 3, 1992, letter, regarding the applicability of the pretreatment metal finishing requirements at 40 CFR Part 433 to the testing of production workpieces using x-ray examination to detect structural flaws. You asked whether x-ray examination and the associated wastewater from the photographic processing of x-ray images is considered "testing" as that term is used under 40 CFR 433.10(a). Silver is the primary pollutant of concern in this wastewater.

This was a difficult question to answer. Our field experience has shown that testing operations are tightly integrated with metal finishing operations at many facilities. In addition, the supporting regulatory material does not clearly address testing operations. We have, however, closely reviewed the history of the Agency's metal finishing rulemaking, including the Development Document, and conclude that the Agency did not intend to regulate x-ray examination and its photographic processing wastewater as "testing" under 40 CFR 433.10(a). Consequently, this wastewater is not subject to the metal finishing requirements under 40 CFR Part 433.

Page V-49 of the Development Document characterizes "testing" by explaining:

Fuels, lubricating oils, and hydraulic fluids are commonly used in non-destructive performance testing for many products such as engines, valves, controls, and pressure vessels. Oily penetrants are used in dye-penetrant inspection and testing operations. Common penetrants include water, kerosene, ethylene glycol, neutral oil, SAE 10W or SAE 40W oils, water-washable penetrants, color-contrast penetrants, and emulsifiers. Leak testing, final washing (automobiles, etc.) and test area washdowns enter waste streams and may contain oils and fluids used at testing stations as well as heavy metal contamination derived from the component being tested. These wastewaters contribute to the common metals and oily waste types.

In addition, Page V-27 of the Development Document identifies oils as the characteristic waste from "testing," rather than precious metals such as silver. Consequently, we conclude that x-ray photo processing wastewater is not regulated as "testing" under the metal finishing requirements at 40 CFR Part 433.

When x-ray photo processing wastewater is combined before treatment with other wastewater that is regulated under a categorical standard, the combined wastestream formula under 40 CFR 403.6(e) must be used to develop the pretreatment standard for the combined flow. In those cases, x-ray photo processing wastewater is reflected in the formula as an unregulated stream.

The Agency is currently developing new categorical standards and reviewing existing standards to determine whether any changes are appropriate. The metal finishing categorical standards are being considered for revision, and the regulation of x-ray photo processing wastewater from testing operations would be a reasonable addition to the regulations. Consequently, we encourage the City to continue to work with industry to reduce or eliminate these discharges to facilitate future compliance with any new metal finishing pretreatment requirements.

Thank you for your inquiry. If you have any questions regarding this matter, please call me at (415) 744-1907.