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FM 521 PS&E


Drainage Design

  • FM 521 in Fort Bend County was the reconstruction and urbanization of a 5-mile corridor to widen from 2-lane with a dedicated left-turn lane and open ditch section to a 4-lane with protected left-turn lanes with curb-and-gutter section. FM 521 saw the design of 2 detention ponds to offset the increased imperviousness due to the widening of a road and the addition of a grade-separated intersection. one of the ponds was able to be placed under the partial Cloverfield interchange, taking extra care for adequate capacity, operation, and maintenance. the ponds were designed utilizing 3D BIM tools and were designed in full 4D to create detailed grading plans and key locations for the contractor to be able to build easily. All details and connections were made to model to account for all tie-ins including the retaining walls into the pond embankments, and pond inlets and outlets. The project consisted of dual trunklines along FM 521 that outfalls into 3 receiving streams throughout the 5-mile corridor. One of the streams in the corridor was a private irrigation canal, proposed design ensured the flow direction of the ditch would work to maintain the current drainage pattern and not drain into the private channel. The detention ponds were designed to hold back flows higher than their intended design storm and higher berms were placed around the ponds to ensure flows would not escape into neighboring properties but would remain within the project limits. GIS and Lidar were used to supplement the missing ground information. Proper care was made to ensure that Lidar was matching the ground elevations from the survey and matching the verticle datum.

Client: Fort Bend County

Location: FM 521

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