California Code, Public Resources Code - PRC § 25540.3

(a) An applicant for a geothermal powerplant may propose a site to be approved that will accommodate a potential maximum electric generating capacity in excess of the capacity being proposed for initial construction. In addition to the information concerning the initial powerplant and related facilities proposed for construction required pursuant to Section 25520, such application shall include all of the following, to the extent known:

(b) If an application is filed pursuant to subdivision (a) which proposes a site to be approved which will accommodate a potential maximum electric generating capacity in excess of the capacity being proposed for initial construction, the commission may, in its decision pursuant to subdivision (a) of Section 25540.3, either certify only the initial facility or facilities proposed for initial construction or may certify the initial facility or facilities and find the site acceptable for additional generating capacity of the type tentatively proposed. The maximum allowable amount and type of such additional capacity shall be determined by the commission.

If the decision includes a finding that a particular site is suitable to accommodate a particular additional generating capacity, the site shall be designated a potential multiple facility site. The commission may, in determining the acceptability of a potential multiple facility site, specify conditions or criteria necessary to ensure that future additional facilities will not exceed the limitations of the site.