Section 3137.85 - What is the effective date of a participating area?(a) The effective date of an initial participating area is the first day of the month in which you complete a well meeting the productivity criteria, but no earlier than the effective date of the unit.(b) The effective date of a modified participating area or modified allocation schedule is the earlier of the first day of the month in which you file the proposal for a modification or such other effective date as may be provided for in the unit agreement and approved by the BLM, but no earlier than the effective date of the unit. 67 FR 17886 , Apr. 11, 2002, as amended at 73 FR 6444 , Feb. 4, 2008