Maximum permitted density for residential uses. Notwithstanding any provision in this chapter to the contrary, the maximum permitted density for townhouse dwellings permitted by § 160-20.1B(1)(a)[3], twin dwellings permitted by § 160-20.1B(1)(a)[2], or any mix of residential uses permitted by § 160-20.1B(1)(a)[4], shall be not more than 9.25 dwelling units per acre of base site area.