The cluster development shall consist of a lot or contiguous lots under one ownership or control containing a project acreage of a least ten acres or having a potential of at least fifty (50) dwelling units as determined by the provisions of Section 17.54.460. Project acreage shall include only those lands to be used for lots, lands to be owned in common by the residents of the project and lands used for circulation facilities. (Prior gen. code § 8-96.15)