A containment structure for use in automated hydroblasting spray cleaning of a process vessel, the containment structure comprising: a chemically resistant sheet assembly that forms a hood; the hood including a front sheet, a pair of opposing side sheets (44 and 46), a rear sheet, a top sheet, and a floor sheet, each one of the front sheet and side sheets (44 and 46) is adapted for being supported by a skeleton structure; the front sheet has an opening or is adapted for forming an opening therein for mating to an open end of a process vessel end; a front edge of a first one of the side sheets (44 and 46) is adapted to be joined to a first side edge of the front sheet, a front edge of a second one of the side sheets (44 and 46) is adapted to be joined to a second side edge of the front sheet; the top edge of the first side sheet is adapted to be joined to a first side edge of the top sheet, the top edge of the second side sheet is adapted to be joined to a second side edge of the top sheet; a front edge of the top sheet is adapted to be joined to a top edge of the front sheet; a first edge of the rear sheet is adapted to be joined to a rear edge of the first side sheet, a second edge of the rear sheet is adapted to be joined to a rear edge of the second side sheet; a front edge of the floor sheet is adapted to be joined to a bottom edge of the front sheet, a first side edge of the floor sheet is adapted to be joined to a bottom edge of the first side sheet, a second side edge of the floor sheet is adapted to be joined to the bottom edge of the second side sheet, a rear edge of the floor sheet is adapted to be joined to the bottom edge of the rear sheet; wherein the side sheet has a rear height that is less than a front height of the side sheet (44,46) and the rear sheet has a height that is less than a height of the front sheet such that the sheet assembly is adapted for forming the hood over the process vessel end and the sheet assembly is partially open at its rear end, and wherein the containment structure is adapted for housing automated spray cleaning equipment and for containing hydroblasting spray during the automated hydroblasting spray cleaning. a chemically resistant sheet assembly that forms a hood; the hood including a front sheet, a pair of opposing side sheets (44 and 46), a rear sheet, a top sheet, and a floor sheet, each one of the front sheet and side sheets (44 and 46) is adapted for being supported by a skeleton structure; the front sheet has an opening or is adapted for forming an opening therein for mating to an open end of a process vessel end; a front edge of a first one of the side sheets (44 and 46) is adapted to be joined to a first side edge of the front sheet, a front edge of a second one of the side sheets (44 and 46) is adapted to be joined to a second side edge of the front sheet; the top edge of the first side sheet is adapted to be joined to a first side edge of the top sheet, the top edge of the second side sheet is adapted to be joined to a second side edge of the top sheet; a front edge of the top sheet is adapted to be joined to a top edge of the front sheet; a first edge of the rear sheet is adapted to be joined to a rear edge of the first side sheet, a second edge of the rear sheet is adapted to be joined to a rear edge of the second side sheet; a front edge of the floor sheet is adapted to be joined to a bottom edge of the front sheet, a first side edge of the floor sheet is adapted to be joined to a bottom edge of the first side sheet, a second side edge of the floor sheet is adapted to be joined to the bottom edge of the second side sheet, a rear edge of the floor sheet is adapted to be joined to the bottom edge of the rear sheet; the front sheet has an opening or is adapted for forming an opening therein for mating to an open end of a process vessel end; a front edge of a first one of the side sheets (44 and 46) is adapted to be joined to a first side edge of the front sheet, a front edge of a second one of the side sheets (44 and 46) is adapted to be joined to a second side edge of the front sheet; the top edge of the first side sheet is adapted to be joined to a first side edge of the top sheet, the top edge of the second side sheet is adapted to be joined to a second side edge of the top sheet; a front edge of the top sheet is adapted to be joined to a top edge of the front sheet; a first edge of the rear sheet is adapted to be joined to a rear edge of the first side sheet, a second edge of the rear sheet is adapted to be joined to a rear edge of the second side sheet; a front edge of the floor sheet is adapted to be joined to a bottom edge of the front sheet, a first side edge of the floor sheet is adapted to be joined to a bottom edge of the first side sheet, a second side edge of the floor sheet is adapted to be joined to the bottom edge of the second side sheet, a rear edge of the floor sheet is adapted to be joined to the bottom edge of the rear sheet; wherein the side sheet has a rear height that is less than a front height of the side sheet (44,46) and the rear sheet has a height that is less than a height of the front sheet such that the sheet assembly is adapted for forming the hood over the process vessel end and the sheet assembly is partially open at its rear end, and wherein the containment structure is adapted for housing automated spray cleaning equipment and for containing hydroblasting spray during the automated hydroblasting spray cleaning.