The Board of Aldermen has approved two easements for the Parcel F property off Concord Street. One easement will allow about 3 acres near Pennichuck Middle School to be used as an athletic field. The second will preserve an additional 3 acres as conservation land. The 33-acre property known as Parcel F was said to be the last large plot of undeveloped land in the city. It was sold to the developer of a senior citizen housing complex by Pennichuck Corp. two days before the city acquired the regional water-supply company in January.