Freese and Nichols’ design services for Sugar Land’s Dulles Avenue reconstruction included modeling existing and proposed conditions using XP-SWMM software. The existing storm drain outfall for the 1.3-mile major roadway was undersized and could not convey 100-year discharges. Freese and Nichols designed a splitter box and a parallel storm drain system that will provide adequate capacity minimizing construction and property acquisition costs. The project also included analysis of surface detention and additional underground storage as mitigation alternatives. Freese and Nichols designed a combination of larger storm drain conduits and plate restrictors to act as orifices that would mitigate any increase in discharges.