Respondent has owned and operated a chemical manufacturing facility since at least January 2013. The facility manufactures chlorine, sodium hydroxide, solid sodium hydroxide, hydrochloric acid and calcium hypochlorite. The Facility is primarily a manufacturer of chlorine, which is produced through the electrolysis of a sodium chloride being derived from a salt vein deep under the Facility. Brine is pumped to the surface, treated, and transferred to one of three electrolysis production units. Chlorine gas is produced, dried, liquefied, and compressed. Hydrogen is created as part of the electrolysis and is used as a fuel or in the hydrochloric acid unit. On January 24, 2017, EPA inspected the Facility to determine whether Respondent complied with the RMP Regulations. Based on the observations of EPA inspectors during the Inspection, EPA has determined that Respondent has the potential to store as much as 27,000,000 pounds of the toxic chemical chlorine in the form of liquefied chlorine gas at the Facility in pressurized storage vessels, ranging in capacity from 180,000 pounds to 700,000 pounds. Based on the observations of EPA inspectors during the Inspection, EPA has also determined that the Facility produces hydrogen gas during the electrolysis process. Respondent uses as much as 88 pounds of hydrogen gas at any one time. Hydrogen, CAS No. 1333-74-0, is an extremely hazardous flammable gas, which is also listed in accordance with CAA Section 112(r)(3), 42 U.S.C. § 7412(r)(3), at 40 C.F.R. § 68.130, Table 3, and thus is a regulated substance in accordance with CAA Section 112(r)(2), 42 U.S.C. § 7412(r)(2).