In accordance with RCW 35.42.010 through 35.42.220, a county with a population of six hundred thousand or more may lease space and provide for the leasing of such space through leases with an option to purchase and the acquisition of buildings erected upon land owned by the county upon the expiration of lease of such land. For the purposes of this section, “building,” as defined in RCW 35.42.020 shall be construed to include any building or buildings used as part of, or in connection with, the operation of the county. The authority conferred by this section is in addition to and not in lieu of any other provision authorizing counties to lease property.