Electrical Duct Banks and Service Entrances in Texas

Fifty-foot earthen levees flank the Trinity River through Dallas, and the water they hold back is a useful reminder that the ground under a Texas data center is rarely neutral. Duct banks run underground for hundreds or thousands of feet between the utility, the substation, the generators and the building, and every foot of that route crosses soil, water and other utilities. A duct bank is a concrete-encased set of conduits that carries power and communications cable, and once it is buried, it is nearly impossible to change.

A service entrance is where those cables reach the building: the underground stubs, the manholes and pull boxes, the entrance rooms and the penetrations through slab and wall. For a data center, there are several of them, because power and fiber each need diverse paths, and the redundancy that the building promises inside has to be matched by the paths that bring services in.

We design the underground route as a system, not as a series of trenches, and we build it with the care that something unrepairable deserves.

The route begins as a drawing of every utility, structure and obstacle between the source and the destination. We walk it with the electrical engineer, mark the existing utilities, and ask where a path is shared and where it is separate. Diverse paths for redundant feeds must be separated by enough distance that one dig-in or one flood cannot take both. The route also has to leave room for future expansion, with spare conduits and space for additional duct banks.

Once the route is agreed, we plan the trench: depth, width, spoil handling, shoring and dewatering. The method depends on the soil and the water table. We then sequence the installation so that open trench is minimized, with duct, spacers, reinforcement and concrete encasement installed in short runs and backfilled before the next section opens. Our utility and substation site work package connects at the upstream end of the route.

The physical work includes excavation, bedding, conduit placement with spacers, reinforcement where required, concrete encasement or controlled backfill, and warning tape. Manholes and pull boxes are set at changes of direction and at intervals that match the cable pull limits. At the building, we install entrance sleeves, wall and slab penetrations, and seals that keep water out of the conduit.

Diverse fiber entrances use the same method. The work overlaps with fiber and telecom trenching, and when the routes share a trench corridor, we coordinate to keep power and communications conduits separated as the design requires. Where the duct bank serves a generator, the section is described under generator yards and fuel systems. Each run is mandrelled, proven clear and labeled before it is accepted.

Texas weather tests buried work. El Paso Water reports that a 2006 storm dropped a year's worth of rain on El Paso in two days, causing more than $200 million in damage to businesses and homes and $115 million in damage to the city's stormwater system. A duct bank in an arroyo or low spot must be designed for the water that can arrive, with encasement and drainage that prevent a flooded manhole or a washed-out trench.

Soil movement is another factor. In The Woodlands, Harris-Galveston Subsidence District data cited in a May 2026 report show localized pockets of subsidence from groundwater removal that compacts aquifer clay and is permanent. A rigid duct bank next to a settling building can shear where it enters, so we use flexible couplings, sleeves and designed transitions. The geotechnical report and the structural design tell us where the movement is most likely to occur.

Underground work is where mistakes are hidden, so we keep it under close supervision. We survey the route before and after installation, record the locations of every conduit and manhole and photograph the trench before backfill. Proof pulling, mandrel testing and megger tests of installed cable are done and logged.

We also keep the utility locate process disciplined. Before any dig, utility locates are requested and verified, and where existing lines are near the route, we use hand digging or vacuum excavation. At the end of the job, the owner receives as-built drawings that show the actual route and depth, which becomes the record for any future excavation. For campus owners with several buildings, that record is essential.

Duct banks and service entrances should be finished before slabs and paving are placed over them. A missing conduit under a finished slab means coring or a surface trench, both of which cost time and risk. We therefore sequence underground work ahead of the slabs, and we coordinate with the cable pull schedule, which can only start after the manholes and conduits are accepted.

Long cable lead times, utility locates and weather all affect the sequence. We keep a lookahead for the owner's electrical contractor showing when each run will be ready, and the pad, enclosure and duct bank schedules are reviewed weekly. For central plants, see central utility plant; for owners who run several sites, enterprise and financial institutions describes the standards they often apply. The Trinity corridor, and the market around Dallas, demonstrates how local ground and water shape the plan.

Send the route, the source and destination points and any existing utility maps. We will return a trench method, a duct bank detail suited to your soil and a sequence that puts underground work ahead of slabs and paving.

Why encase a duct bank in concrete?

Concrete protects the conduits from damage, holds them in position and helps carry loads from above. Some designs use controlled low-strength backfill instead. The engineer chooses based on the cable, the heat the cable produces and the site loads. We install either method with spacing and reinforcement as specified.

How do you keep diverse paths truly separate?

By distance, route and sometimes crossing points. We map each path and check where they share a corridor, a manhole or a crossing. The design engineer defines the separation required, and we survey the as-built route to confirm it.

What happens if we hit an unmarked utility?

We stop, secure the area and notify the owner and utility. Prevention is much better: locates are requested early, existing lines are potholed, and hand digging is used near them. Our records of the route help future crews avoid the same problem.

Can spare conduits be added later?

Yes, if they are planned. We recommend building spare conduits and sleeves in the first phase, and leaving space and easements for additional duct banks. Adding conduits later usually means reopening trench and working around live cable.

How do you handle high water tables?

With dewatering, shoring and short open sections, so that conduits are placed and encased in dry conditions. In very wet soils we may use alternative methods or sequence work for drier seasons, and we describe the schedule effect to the owner.