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i s, UNITED STATES ENVIRONMENTAL.PROTECTION AGENCY o _Uj WASHINGTON, D.C. 20460 PROI�GS\O i I i OFFICE OF h SOLID WASTE ARD SEP 2 2 20JQ EMERGENCY RESPONSE MEMORANDUM SUBJECT: Regulatory Status of Undergro 4ExhaustFluid Tanks FROM: Carolyn Hoskinson,DirectorOffice of Underground Sto Ta T0: EPA UST/LUST Regional Program Managers State UST Program Managers This memorandum responds to questions from states on the regulatory status of underground storage tanks(USTs)containing diesel exhaust fluid(DEF). Specifically, states have asked Waether EPA regulates USTs containing DEF under the federal UST regulations in 40 CFR Part 280. According to these regulations,an UST is regulated if it contains petroleum or hazardous substances;however, a number of UST systems are excluded from the Part 280 requirements. One of the exclusions applies to"[a]ny UST system that contains a de minimis concentration of regulated substances"(§280,10(b)(5)), The regulations do not specify a de minimis quantity,but do allow the implementing agency to determine de minimis concentrations on a case-by-case basis. I DEF is a 32.5 percent aqueous solution of urea used in Selective Catalytic Reduction (SCR)technology as one way to reduce nitrogen oxide emissions from heavy-duty diesel engines,as required by EPA's"2007 Heavy-Duty Highway Rule." Although aqueous urea is neither petroleum nor a hazardous substance,the DEF solution may contain a small amount of ammonia,which is a regulated substance. According to DEF manufacturers,any amount of ammonia present in DEF is considered to be a contaminant. To address this contamination concern,the industry has set a very strict limit on the maximum amount of ammonia allowed in solution. The international standard for DEF allows no more than 0.2 percent by weight of alkalinity,measured as ammonia,to be present in solution. Although 0.2 percent is the maximum allowed limit according to the international standard,manufacturers indicate that the actual amount of ammonia in solution should be much less than 0.2 percent,and ideally there should be no ammonia in solution. Since EPA expects that the presence of ammonia in a DEF I UST will be minimal, it is EPA's view that DEF USTs meet the de minimis exclusion and thus are not regulated as hazardous substance USTs under the federal UST regulations. lntemetAddress(URL)e hap:/,'Wny,epa.gov Recychd/Recyclable a Printed wim vegetable Oil8ased Inks on 100%Postconsumer,Process chicane Frey Recycled Paper I