Senate committee substitute replaces 1st edition with a new act TO REVISE SYSTEM DEVELOPMENT FEES. Changes short title to "Clarify System Development Fees." Amends GS 162A-205(7), which governs the imposition of system development fees, to require that the planning horizon used to calculate the fee is not less than five years (was, not less than 10 years). Effective October 1, 2018, and applies to system development fees established or updated on or after that date.

Amends GS 162A-211, allowing for revenues from system development fees that are pledged to secure revenue bonds to be used in accordance with the bond order, resolution, trust agreement, or similar instrument authorizing and securing the bonds until all of these revenue bonds are no longer outstanding. Makes other clarifying changes. Effective July 1, 2018, and applies to system development fees pledged on or after that date. 

Amends GS 162A-213, differentiating development fees for land subdivision and other new development. For new development involving the subdivision of land, the system development fee will be collected by a local government unit at the later of either the time of plat recordation or when water or sewer service is committed by the local governmental unit. For all other new development, the local governmental unit will collect the fee at the earlier of either the time of application for connection of the individual unit of development to the service or facilities or when water or sewer service is committed by the local governmental unit. Effective July 1, 2018, and applies to system development fees collected on or after that date. 

Requires the Environmental Management Commission to update the gallons per day usage under the two specified rules to reflect how new construction uses less water and sewer than under the current rule. The amended rules must take effect by January 1, 2020.