SH 121/DNT Interchange in Collin County, Texas (PS&E), NTTA
IEA provided plans, specifications and estimates (PS&E) for this project. Services included the hydraulic impact study, gantry design, temporary drainage system, utility coordination, removal plans, and a Storm Water Pollution Prevention Plan (SW3P). The project includes mainlane widening, 10 ramps, 8 direct connectors, and 5 toll gantries. The project also required conversion from an existing cash and electronic toll plaza to an all electronic toll gantry.
Toll Gantry Plans: Toll gantry design is one of our specialties. Our engineers provided oversight of the toll gantry plans for this project. The final design of all five gantries was completed per NTTA standards. The PS&E package included design of the electrical service center, tolling systems, and data lines. Our structural design team was responsible for the structural and foundation designs for locations where the gantry span or height exceeded the NTTA standard. We also coordinated with the bridge designers at locations where the gantry was mounted to the bent columns.
In coordination with NTTA’s IT department, their consultants, and the roadway designers to locate the tolling sites and to connect with existing IT infrastructure, IEA engineers prepared the tolling equipment layout and conducted site determinations to capture the needs of the driving public. Our designing process on each gantry included all the civil, structural, electrical and foundation designs, transfers, loops, electrical service centers, and maintenance access. We were cognizant of the need for driving sight distance, the roadway profile, conflicts with existing and future utilities, and other roadway elements. All of the gantries were built with VES cabinets, VES cameras, PTZ cameras, AVI antennas, and RF Module with conduits and equipment support conduits.
Utility Coordination: IEA studied the improvements proposed for this interchange and their relationships with existing utilities to help identify potential conflicts. Once the conflicts were located, IEA lead the effort to confirm the conflicted areas. Working closely with the roadway and bridge designers, as well as the utility companies, IEA provided solutions to pending utility conflicts in an effort to reduce the amount of relocations.
IEA also provided conceptual schematic design for this interchange. The new designs will allow two-lane connectors in the directions with high volume traffic. The design changes also eliminated the need for reconstructing recently built ramps along SH 121 on the west side of the Dallas North Tollway (DNT), and outside widening of recently built overpass bridges over Preston Road and Parkwood Blvd. Schematic design included 10 ramps, 8 direct connectors, and 5 toll gantries.
This provided the City of Plano with a quality, accelerated schedule for roadway design and extensive hydraulic analyses.