HMT Associates, L.L.C. — Hazardous Materials Safety Interpretation

Page 1400 Seventh Street, S.W. of Transportation U.S. Department Washington, D.C. 20590 Research and Special Programs Administration MAY 1 2 1999 Mr. Gordon Rousseau Reference. No. 98-0314 HMT Associates, L.L.C. 1850 K Street, NW Washington, DC 20006-3500 Dear Mr. Rousseau: This is in response to your letter dated October 16, 1998, and October 26, 1998 telephone conversation with Ms. Eileen Mack of my staff, concerning a requirement in 49 CFR 173.33(a)(2) against loading materials on the same cargo tank motor vehicle that, if mixed, would cause would an explosion, vehicle fire, excessive increase in pressure or heat, or the release of toxic vapors. You described a situation in which a multi-cargo tank motor vehicle is loaded with two materials that would significantly react when mixed. These materials are separated by a middle compartment containing a neutral, non-regulated material. You asked if this loading arrangement is acceptable Based on the information you provided, the answer is no. The restriction in § 173.33(a)(2) pertains to the loading of incompatible materials on the same cargo tank motor vehicle. Therefore, the restriction applies regardless of whether the incompatible materials on the cargo tank motor vehicle are separated by a compartment containing a neutral material. I hope this satisfies your request. Sincerely, Michel Hattie L. Mitchell Chief, Regulatory Review and Reinvention Office of Hazardous Materials Standards $173.33 980314#

Page 2маск • i' HMT ASSOCIATES, LLC $173.33 1850 K STREET, N.W 980314 WASHINGTON, D.C. 20008-3500 :. SUITE 200 PATRICIA A. QUINN E.A. ALTEMOS (202) 463-3511 GORDON ROUSSEAU FACSIMILE (202) 463-3512 WRITER'S DIRECT DIAL NUMBER e-mail address (202) 463-3511 gorrou@pipeline.com Friday, October 16, 1998 Mr. Edward T. Mazzullo Director Office of Hazardous Materials Standards Research & Special Programs Admn. Department of Transportation Washington, DC 20590 Dear Mr. Mazzullo: The DOT hazardous materials regulations in paragraph § 173.33(a)(2) state: "Two or more materials may not be loaded or accepted for transportation in the same cargo tank motor vehicle if, as a result of any mixture of the materials, an unsafe condition would occur, such as an explosion, fire, excessive increase in pressure or heat, or the release of toxic vapors." A client is considering using a three-compartment vehicle to transport 1700 gallons of an compartment no. 2, and 1500 gallons of a hypochlorite solution in compartment no 3. While it is acid solution in compartment no. 1, 2300 gallons of a neutral, non-regulated solution in agreed that the materials in compartment no. 1 and no: 3 could significantly react when mixed, given the extreme circumstances that would be necessary under which they could be mixed, and considering that a neutral material is purposefully loaded between the potentially reactant materials, it would seem that the circumstance described here is not what DOT had in mind in drafting the regulation. Would DOT, therefore, consider the above loading configuration acceptable insofar as the subject rule is concerned? Please call me if clarification is needed. Thank you for your attention to this matter. Sincerely. Gordon Rousseau cc: Dr. C. Ke, DOT/RSPA#