Section 83A. The commissioner is hereby authorized to establish, on land under the control of the department of environmental management or of the metropolitan district commission and upon sites approved by the commissioner of conservation and recreation, camps to which male prisoners, including male prisoners sentenced to life who have served twelve years, except those serving a sentence for life for first degree murder, may be removed for employment, as designated and approved by the commissioner of conservation and recreation, in reforestation, maintenance and development of state forests, who have shown by their conduct and disposition that they would be amenable to less rigorous discipline and would benefit from work in the open air; provided, however, that only one such camp may be established on land within the urban parks district. Before any site for any such camp shall be approved, a public hearing shall be held by the commissioner of conservation and recreation, in a city or town situated within a radius of ten miles of the proposed site.