In any proceeding pursuant to section 16-19 on a rate amendment proposed by a water company, as defined in section 16-1, the Public Utilities Regulatory Authority shall consider including the cost to the company of purchasing, owning or retaining land for water supply protection or future water supply use in the current rate base of the company, subject to the following conditions: (1) The land shall be included in a water supply plan filed and approved pursuant to section 25-32d or shall otherwise be approved by the Commissioner of Public Health pursuant to the general statutes or regulations adopted under the general statutes; (2) the land shall include (A) an area necessary for surface and groundwater supply protection, (B) the impoundment area, (C) a well site, or (D) other appropriate appurtenances such as a tank site or filtration plant site or other necessary facilities; and (3) the purchase, ownership or retention of the land is found by the authority to be prudent considering cost, availability and need. The authority may not require any such company to sell any such land owned by such company as of October 1, 1997, except as provided in section 16-262n.