The Planning Board at its meeting on Thursday will hold a public hearing on a proposed zoning measure to regulate the location of medical marijuana dispensaries in town. Under the draft plan, dispensaries would be allowed in all areas of town that are zoned general industrial, high-rise industrial, or retail industrial, according to Josh Morris, the town’s assistant planner. Burlington has an existing temporary moratorium on medical marijuana dispensaries to allow it time to develop the zoning rules The moratorium is set to expire on June 30. The 2012 state ballot law legalizing medical marijuana allows for up to 35 dispensaries, with at least one but no more than five per county. The state last month awarded 20 initial licenses to open dispensaries, none of which identified Burlington as a location for a facility. The board’s meeting starts at 7:30 p.m., and the hearing is set to begin at that time.