No hospital, school, church, college building, nursing home, rest home, convalescent home, library, museum, and community center or public recreational building shall be closer to any street line than 30 feet. Every principal building shall be on a lot with a minimum width of 150 feet at the street line and a minimum area of 20,000 square feet. Every principal building shall be provided with two side yards totaling 40 feet in width, the minimum width of any side yard being not less than 15 feet. If on-site wastewater disposal is proposed, the minimum lot size shall be one acre provided that the standards of Subsection 26-43.7a, 4 (Water Quality) are met.