Electrical Ductbank – San Antonio, TX

Hydro Spy was recently contacted by one of the top 100 Design-Build firms in the United States to offer solutions for excavating a large trench across several commercial properties.  The trench was needed for the installation of an electrical duct bank, extending from a new multi-level medical facility, across a concrete drive-way and through the lawn of a large bank. The trench would eventually slope into an 8 ft x 8 ft x 13 ft deep manhole that would have to be excavated directly in front of the bank. The trench would slope up from the manhole on the other side and continue for another 250 ft, curving around a cluster of obstructions before ending at the proposed site of the power source.

Normally, the General Contractor would have used a back hoe or mini excavator to cut the trench, but they were ruled out for one reason. The congestion of subsurface utilities posed serious risk to any mechanical means of excavation. A 16″ city water line supposedly paralleled the proposed path of the trench. According to the project’s energy provider, an existing electrical duct bank was said to occupy the area where the new duct bank would be installed.

Because of the rocky soil conditions, it was virtually impossible to probe for utilities with a traditional probing iron. After visiting the job site and meeting the project superintendent, Hydro Spy proposed executing several exploratory swaths across the proposed path of the duct bank before hydro excavating the actual trench. It seemed like added work, at the moment, but Hydro Spy cautioned the general contractor about starting a massive trench that could prove to be unusable if unknown conflicts existed. However, at the end of the day, the contractor laid out the path of the trench and Hydro Spy began excavating 2 ft wide and 5 ft deep.

100 ft into the trenching effort, inspectors determined that the trench was not usable because of the proximity of existing municipal utilities. At this point, rather than move the trench over a few feet, Hydro Spy executed the previously suggested exploratory swaths, exposing other conflicts that would have rendered the second trench unusable. Finally, the exploratory effort provided enough empirical data for the project inspector and superintendent to agree on the best path for the duct bank.

Finally, the hydrovac effort proceeded. Dozens of crossing utilities were encountered along the way, but they were more a nuisance than a conflict for the duct bank. Despite hard ground conditions, including stabilized sand and concrete, Hydro Spy finished the project on time and within budget for the client. Looking at the finished product, inspectors who initially laughed at the idea of using pressurized water to surgically excavate in such rocky soil conditions were thoroughly amazed: “You guys are going to put a lot of diggers out of business.”

For more information about this project or similar projects, please contact the project manager directly.