The term “decontamination,” as used in this chapter, means the reduction of the level of contamination from radioactive material to the level that the department determines is reasonably necessary to eliminate the hazard to public health that is caused by the contamination of any object, building, structure, or premises. Any order by the department pursuant to Section 115185 shall prescribe the level to which the contamination is required to be reduced in order to eliminate the hazard to the public health.