Delta FM 76 Bridge Replacement

Delta FM 76 Bridge Replacement

Project Background

Delta FM 76 is an on-system bridge owned and maintained by the state on the TxDOT highway system. The bridge in El Paso County was aging and needed replacement along Delta Drive between Alameda Avenue and Trowbridge/North Loop. Consor Engineers, LLC brought in HVJ to provide a geotechnical investigation, including the design and recommendations for proposed bridge foundations and stability analyses of the retaining walls.

Practice: Geotechnical Engineering 

Sector:  Roads & Bridges

Location: El Paso County, Texas

Services: Deep Foundations, Retaining Walls, Slope Stability 

Delta FM 76 Bridge Replacement Feature

The Problem

Our primary challenge was the bridge’s location in an area with various infrastructure and limited Right of Way (ROW) access. It’s adjacent to several property owners’ land, including an oil company, a railroad, an electric company, a refinery, and a water plant. There are many types of infrastructure around the bridge, such as power lines, rail lines, and extensive fencing, making working in the area akin to going through a maze! We needed to obtain ROW access for the drill rig equipment necessary for the investigation and to obtain the samples with minimal disruption to the surrounding infrastructure. While ROW access is essential on any project, this project was unusual because it’s rare that so many property owners surround TxDOT property. The project was on a short schedule, and we needed to find a solution quickly. 

The Goal

We aimed to develop geotechnical design and construction recommendations for bridge replacement through collecting soil data. Fully owning the solution is a core HVJ value, so we knew we needed to proactively find a solution to the ROW barrier. This required a hands-on approach and open communication with property owners to instill confidence that our work would cause minimal disruptions.   

Our Solution

Our team conducted an extensive walking field visit (reconnaissance survey) to determine potential options for accessing ROW. We discovered an entry point owned by El Paso Electric, which was initially unknown to the team, that would allow us to bring in the equipment needed to obtain samples. We then worked with the client to determine the right contacts who could grant us ROW access, arranged discussions with the appropriate stakeholders and provided all the information they needed to feel confident in allowing us ROW. We developed a drilling strategy for this location, including an extensive safety plan to access necessary boring locations without ROW access from the other adjacent properties. For most of the borings within the embankment, we drilled on top of the bridge embankment area using an extended depth to ensure the samples provided accurate data. 

The Results

The ROW access allowed us to attain the soil data we needed to complete our work. We provided the recommendations, which included foundation depths and embankment fill requirements, required to move the project forward. 

The El Paso area tends to have soils conducive to cost-effective building, which was the case for the bridge area. A unique finding was that the area contained contaminated soils, likely going back decades to the bridge’s original construction. We followed up with a more in-depth laboratory test to clarify the contaminant and ensure it would not impact the construction. We also researched old documents and construction plans on the bridge to determine the origins of the contaminants. This process allowed us to identify the hydrocarbon contaminant and understand the full context of the situation. We included in our recommendations how to guard against any negative impact through a high-quality fill. 

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