Underground Storage Tanks Program

UST Cleanup Program Approval of a Combined BTEX + Naphthalene Analytical Method

With the UST cleanup program moving to risk-based corrective action (RBCA), there is now a greater emphasis on analyzing soil and groundwater samples for the specific chemical constituents that are thought to present the greatest risk to human health and the environment. For petroleum releases, these contaminants of concern are typically aromatic compounds like benzene, toluene, ethylbenzene and total xylenes (BTEX), and polynuclear aromatic hydrocarbons (PAHs) like naphthalene (N) and benzo(a)pyrene. One of the concerns, both of the Department and of the regulated community, is that using RBCA will result in significant increases in analytical costs. Because the Department's experience at UST cleanup sites has shown that in many cases the only PAH to be a contaminant of concern is naphthalene, the Department has looked into the possibility of using a single analytical method to test for BTEX + N. After standard PAH analyses during the site investigation confirm that naphthalene is the only PAH of concern at a site, subsequent analyses could employ the combined BTEX + N method to reduce analytical costs.

At the request of the tank program, DEQ's laboratory has tested the utility of BTEX analytical methodology for detecting naphthalene. Their tests confirmed that N can be analyzed to currently acceptable reporting limits with no modification to the method other than to include N on the compound list and in the composite standard. Since the Department is allowed under OAR 340-122-242(5)(f) to approve alternative analytical methods which are applicable to the compounds of interest and which have detection limits comparable to existing methods, the UST Cleanup Program is granting approval of the use of this modified BTEX+N method.

Parties considering the use of the BTEX+N method should be aware that the Department does NOT consider this method to be appropriate for an initial site investigation. Sufficient data must first be collected from standard BTEX and PAH analytical methods to clearly demonstrate that naphthalene is the only PAH which is present at levels of concern. BTEX+N can then be used for subsequent monitoring. Depending on conditions at the site, the Department may require final confirmatory samples to be analyzed with the standard BTEX and PAH analytical methods.

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