Every conduit in a duct bank is a decision you cannot revisit once the concrete is placed. An industrial plant's electrical service, feeder paths to production areas, controls and communications all run through the ground in conduit, and mistakes in count, size, spacing or routing are expensive to correct after backfill. We build duct banks on industrial sites as precision work, from the staked route to the final mandrel test.
A typical package includes the service entrance conduits from the utility transformer pad to the main switchgear, feeder duct banks to remote buildings, equipment pads and process areas, lighting and security conduits, telecom and fiber paths, and the manholes and pull boxes that make later pulls possible. We install concrete encasement with reinforcement where the design requires it, set spacers to hold separation, and mark and photograph every run.
We coordinate with the electrical contractor from the start. The count of spare conduits, the bend radius for large cable, the location of the pull boxes and the grounding conductor are all agreed in a pre-pour review. The goal is a system that the electrician can pull through on the first attempt and that maintenance can extend without trenching a new route.
What goes into the ground
The duct bank starts with trench excavation to the elevation on the plans, usually below frost depth and clear of other utilities. We install a compacted bedding layer, set conduit with spacers at the required intervals, wire or strap it to hold position during the pour, and place concrete in a controlled sequence. Red-dyed concrete or warning tape above the bank marks the location for future excavators.
Large industrial services use rigid conduits in banks of six, nine or more, and pull boxes sized for the largest cable bending radius. Transformer pads, switchgear pads and generator pads receive stub-ups cast to the manufacturer's drawings. Our equipment pads and foundations scope includes pads and conduits planned together so alignment is exact, then we cap, tag and protect every stub until the cable is pulled.
Checks before the concrete
We hold a pre-pour inspection with the electrical contractor, the engineer of record and, where required, the utility. The checklist includes conduit count and size, spacing, slope to drainage points, joint cement, grounding, spare conduits, pull string, marker tape, depth, and clearances to other utilities. A duct bank approved by all parties is photographed before it is covered.
Heat is part of the design. Cables in a concrete-encased bank shed heat to the surrounding earth, and the ampacity the engineer calculated assumes a specific arrangement of conduits, spacing, depth and soil thermal conditions. If we change spacing in the field or substitute a different backfill, the rating may fall. For that reason we hold the layout to the drawing, and we ask the engineer for approval before any change in conduit arrangement, however small it looks on site. After the pour we proof every conduit with a mandrel and a brush, leave a pull string in place and cap the ends. Any conduit that does not pass is repaired before backfill. The mandrel records go into the turnover package, which gives the electrician and the owner confidence that the paths are open.
Power demands in Colorado
Power demand is a defining feature of Colorado's newer industrial projects. The rail mill that broke ground in Pueblo includes a 240 megawatt on-site solar field, and the 30 megawatt Alamosa Solar Generating Project near Alamosa entered commercial operation on May 10, 2012, supplying customers of Public Service Company of Colorado. On-site generation and utility-scale generation both change how a site connects to the grid, and both rely on underground cable systems.
Industrial owners in Pueblo and across the Front Range now ask for more power than their predecessors did, and they ask for it with more redundancy. Data centers and electrified process lines push the service size higher, so duct banks are often designed with generous spare capacity. We help owners decide where extra conduits are inexpensive now and costly later.
Electrical codes in Colorado
Electrical editions are set at the state level while building codes are set locally. Mesa County, for example, lists the 2024 International Building Code as its adopted code and notes that the 2026 National Electrical Code and the 2024 Colorado Plumbing and Fuel Gas Code take effect January 1, 2027. Lakewood's permit handout lists the 2021 IBC, 2021 IRC, 2021 IFC, 2021 IEBC and 2023 NEC as adopted codes, with local amendments in Title 14 of its municipal code. Lakewood shows how a city lists both its building and electrical editions in one place.
We build to the edition the permit states and to the utility's own service requirements, which can be stricter than the code. The utility specifies the transformer pad, clearances, conduit type and sometimes the contractor qualifications for service work. Their standards are obtained early and the duct bank design is checked against them before the first trench. Where a project is sited in a jurisdiction that has not yet moved to the edition the design assumes, we write the edition into the permit drawings so the inspector and the electrical contractor are reading the same requirement.
Cost drivers for underground electrical
Length, conduit count, depth and soil conditions set the price. Rock, groundwater and crossings with existing utilities raise the cost of trenching. Concrete encasement is a material and labor item that scales with the number of conduits. The cost of spare conduits is small compared with the cost of reopening a roadway or trenching through finished pavement later.
We prepare options. A direct-buried conduit system with sand backfill costs less than a concrete-encased bank, but offers less protection under truck traffic. We show the difference and tell you when yard lighting and electrical site work and other site electrical should share the same corridor and when they should be separate to simplify maintenance.
Plan the power path first
Send us the single-line diagram and the site plan. We will return a duct bank layout with conduit counts, spares and a schedule.
Common Questions
How many spare conduits should we install?
As many as the economics support. The marginal cost of a spare during the initial trench is low compared with trenching later. We recommend a spare count based on the expansion plan and the type of loads you expect to add.
Should the duct bank be concrete-encased?
Under roads, truck courts and heavy-traffic areas, yes, in most designs. In landscaped or protected areas, direct burial may be adequate. The engineer of record decides based on loading, depth and the utility's requirements.
Who installs the cable?
The electrical contractor pulls the cable. We prepare the conduit system so that the pull is smooth, and we coordinate the schedule so the pulls take place before pavement is placed over the bank.
Can you work with the utility's service requirements?
Yes. We obtain their construction standards, submit our design for review if required, and schedule the utility's inspections. We also coordinate the transformer set and energization date.
What testing is done before backfill?
Conduit mandrel and brush tests, visual inspection by the engineer and electrical contractor, and utility inspection when required. We photograph the work and keep the records.