; (2) set benchmarks for maximum allowable percentage of vacancies, and a maximum ratio of trainees to authorized representatives; (3) utilize double encumbrance or early replacement hiring for authorized representatives and technical specialists; (4) implement tracking systems to assure that staffing levels of authorized representatives and technical specialists do not fall below the minimum required to conduct necessary inspections, thoroughly review mine plans, and conduct accident and special investigations; and (5) identify resources necessary to implement such plan. Such succession plan shall be updated biennially.