Section 3. An owner of land abutting on a public improvement and liable to assessment therefor under this chapter may give notice in writing to the board, within three months after the award of damages is made, that he elects to surrender his land; and if said board adjudge that the public convenience and necessity require the taking of such abutting estate for the improvement named, they may take the whole thereof, and shall thereupon estimate its value, excluding the benefit or advantage accruing from such improvement; and such owner shall convey the estate to the body politic or corporate on behalf of which the assessment was made and may recover therefrom in contract the value so estimated. The commonwealth, county, city, town or district may sell any portion of said land which is not needed for such improvement.