North Tarrant Expressway (NTE) Design/Build Project, Segment 3A Drainage,
Tarrant County, TX

IEA is the Drainage Task Leader for Segment 3A of the North Tarrant Expressway Design/Build project.

Project limits include the IH 35W corridor from north of the North Tarrant Parkway to and including the IH 35W/IH 820 Interchange, then south of this interchange along the IH 35W corridor to Luella Street in the City of Fort Worth, Texas. The project includes 14-16 lanes, with 5 general purpose lanes in each direction and 2-3 managed lanes. There are 10 existing cross-drainage structures which include six FEMA streams, three bridge class culverts, and three bridge crossings. IEA used HEC-HMS and rational methods for hydrologic calculations and GEOPAK drainage, and HEC-RAS and HY-8 for hydraulic analyses.

A reservoir routing model was built for detention pond analysis. Scour analyses were conducted for all bridge crossings. MicroStation and GEOPAK were used for plan production. All design efforts are being completed in collaboration with the structural, roadway, and MOT discipline leaders to ensure a complete PS&E package is provided to the construction team.

IEA reviewed the previous drainage studies for the area, determined existing hydrologic conditions, and then determined proposed conditions. Peak flows and runoff hydrographs for existing and proposed conditions were calculated using HEC-HMS. The storm sewer system was designed using GEOPAK Drainage software. Detention ponds were used to mitigate increases in runoff, and the ponds were analyzed using HEC-HMS.

The hydraulic analysis included the analysis of 10 existing cross-drainage structures, which include six FEMA-studied streams, three bridge class culverts, and three bridge crossings. HEC-RAS (v4.1.0), and HY-8 were used for hydraulic analyses. HEC-RAS was used to complete scour potential analyses for all bridge crossings. IEA designed all of the proposed storm sewer and appurtenances associated with the proposed roadway improvements. IEA analyzed and designed four culverts. Approximately 10,000 linear feet of storm sewer was designed.