The United States Environmental Protection Agency ( EPA ), Region 9, issues the enclosed Administrative Order ( Order ) to Sipaulovi Village ( Village ) for violations of the federal Safe Drinking Water Act ( SDWA ), 42 U.S.C. Section 300f et seq., at the Lower Sipaulovi/Lower Mishongnovi and Upper Sipaulovi/Upper Mishongnovi public water systems ( Systems ), which the Village owns and/or operates on the Hopi Indian Reservation. Pursuant to this Order, EPA has determined that the Systems are out of compliance with the maximum contaminant level for arsenic at 40 C.F.R. Section 141.62(b), the monitoring requirements for arsenic at 40 C.F.R. Section 141.23, and the Tier 2 public notice requirements at 40 C.F.R. Section 14 1.203.