Section 12. If sections one to seven, inclusive, have been complied with, and payment of the expense of the improvements has been arranged under section nine or ten, the commissioners shall carry out said improvements in such manner as the board may approve. The commissioners may employ suitable persons to perform the work under their direction. So far as may be necessary to effect the improvements as approved by the board, the commissioners may take on behalf of the district, in the manner provided by chapter seventy-nine, lands, easements and rights in lands, if the improvements are for a public use, and may purchase and convey real and personal property both within and beyond the limits of the commonwealth. Any person damaged in his property by any action under this or the following section may recover his damages from the district in the manner provided by said chapter seventy-nine and such damages shall constitute a part of the total expense of the improvements.