California Code, Public Resources Code - PRC § 5404

In the event that the park land and facilities are acquired, the operating entity shall acquire substitute park land and facilities.  If, however, less than 10 percent of the park land, but not more than one acre, is acquired, the operating entity may, instead of acquiring substitute park land and facilities, improve the unacquired portion of the park land and facilities, using the funds received for this purpose, after holding a public hearing on the matter and upon a majority vote of its legislative body.