Site and civil work
Underground Utilities and Heavy Equipment
Trenching, duct banks, conduit, transformer pads, boring, backfill and restoration, self-performed.
On most commercial sites the electrical scope starts in the dirt. APS and SRP design the underground, then hand the trench, the conduit and the transformer pad back to you to build, inspect and pay for. Neither energizes anything until its inspector has seen that trench open.
Who trenches, who pays, who energizes
The commonest bid error on a new service is assuming the utility builds the underground. It does not. SRP Rules 4.6.2 and 4.6.3(b) put all trenching, backfill, boring and conduit for an underground service lateral on the customer or developer; where SRP does that work instead, it returns as a contribution in aid of construction. APS ESRM Section 500 is just as plain: customers install the conduit from the service equipment to the transformer pad or j-box, and contact APS before trenching to learn what the trench has to look like.
What the utility keeps is narrow and absolute: the design, the staking, the drawing review, the inspections, the transformer, the meter, the CTs and the test switches. Only utility employees energize.
| Item | Who does it |
|---|---|
| Underground design, trench route, equipment locations | APS or SRP |
| Property corners, grade stakes, blue tops | Customer |
| Trench, bedding, backfill, boring, restoration | Customer |
| Conduit from service equipment to pad or j-box | Customer |
| Transformer pad, ground rod, pad backfill | Customer |
| Trench and conduit inspection before backfill | Utility inspector |
| Transformer, primary, meter, CTs, test switches | Utility |
| Energizing | Utility employees only |
Confirm the serving utility before pricing any of it. SRP's city list reads "served all or in part" and APS serves parts of the same cities, so a ZIP code settles nothing. Downtown Mesa is the trap: the City of Mesa runs its own municipal electric utility over roughly 5.5 square miles. More on the service area page.
Arizona 811, private utilities and caliche
Arizona 811, which everyone in the field still calls Blue Stake, has to be notified before excavation; APS requires contact at least three days ahead. Understand what the ticket buys. It locates member facilities in the public system, not private facilities on private property, and a developed site is full of those: irrigation mains, site lighting a previous contractor put in, fiber between buildings, abandoned conduit nobody recorded. Those get found by potholing, which we price as an allowance and say so in writing.
The thing that wrecks a trenching schedule here is caliche — cemented carbonate hardpan that is a thin crust in one place and, fifty feet away, thick enough to stop a chain trencher and put a hoe ram on the excavator. It is a production-rate problem, not a code problem, and the honest fix is contractual: the geotechnical report if one exists, a unit price for unclassified excavation if it does not.
It is also a backfill problem. NEC 300.5(F) bars backfill containing large rocks, paving materials, cinders or sharply angular material where it could damage the raceway or cable. Broken caliche is exactly that, so spoil leaves the site and select bedding comes in — both line items. At a transformer pad SRP goes further, requiring CLSM backfill per MAG Section 728 with its inspector approving subgrade first.
Cover depth is a table, not a rule of thumb
NEC Table 300.5(A) sets minimum cover by wiring method and by what sits above the trench, which is why a site lighting circuit crossing a parking lot is not one uniform depth.
| Location | Direct burial | RMC or IMC | PVC for direct burial |
|---|---|---|---|
| All locations not specified below | 24 | 6 | 18 |
| In trench below 2 in. of concrete or equivalent | 18 | 6 | 12 |
| Under streets, roads, alleys, driveways, parking lots | 24 | 24 | 24 |
| Under a 4 in. exterior slab, no vehicular traffic | 18 | 4 | 4 |
Two consequences estimators miss. Everything under a street, driveway or parking lot goes to 24 inches regardless of wiring method, so the crossing deepens even where the run does not. And the utility's own lateral is not governed by this table at all: NEC 90.2 puts installations under the exclusive control of an electric utility outside the Code, so that detail comes from the ESRM or ESS. One site, two standards, one trench.
The rest of 300.5 is where inspections fail. The inside of an underground raceway is a wet location, so conductors must be listed for one. Raceways emerging from grade need protection from the required cover depth to at least 8 feet above finished grade under 300.5(D), and raceways entering a building are sealed under 300.5(G). Above 1000 volts the rules move: in the 2023 NEC Phoenix enforces, they sit in Article 305.
Duct banks and transformer pads
A concrete-encased duct bank is cheap to build and expensive to fix. Ours get spacers at the specified interval, sweeps turned the right way for the pull, a rope in every duct including spares, and a mandrel pulled before the pour. Proving a duct after the concrete sets is not proving. It is discovering.
Transformer pads are where utility standards get specific, and SRP Section 7 is worth reading before the civil drawings are finished. Three-phase pads are pre-cast to the size on the SRP design; the customer installs the pad, the secondary window cover plate where required, the ground rod and all conduit and backfill. The ground rod is 5/8 inch by 8 feet, copper-clad, in the high-voltage opening, 2 inches above the pad. Conduits stub 2 inches above the final pad surface with temporary plugs — plugs, the standard says, not duct tape. More than 13 conduits means a pull box under the secondary window, and the finished pad stands at least 4 inches above grade.
The clearance is what collides with the civil set. SRP requires 12 feet of clear working space at the front of a pad-mounted transformer, 3 feet at the sides and 18 inches at the back, and 3 feet kept clear around all edges for the life of the easement. Cheaper to catch on a drawing than after the curb is poured.
One duct bank issue only appears under load. Ampacity underground is a thermal problem: heat leaves through the concrete, then the soil. The underground tables in NEC Informative Annex B — informative, not mandatory — assume an earth ambient of 20°C and a soil thermal resistivity of 90. Phoenix soil at duct-bank depth is not at 20°C in July, and dry native soil moves heat poorly. Ask before the pour, not after the first summer. Gear at the far end sits under service and distribution.
Monsoon, heat and sequencing
The monsoon is a scheduling constraint, not weather trivia. An open trench meeting a storm cell is a collapsed wall, a floated conduit, washed-out bedding and a day of pumping. The overwhelming majority of Arizona's cloud-to-ground lightning falls in the three monsoon months, which is also when a crew stands in a wet ditch beside steel.
So the sequencing is deliberate: open only what can be inspected and closed in the same window, keep conduit capped until the pull, book the utility inspection before the trench is open, and backfill behind the pull instead of leaving proved duct open across a weekend. Where a forecast runs against a trench that cannot be closed, plating and shoring go into the plan and into the number.
Heat runs the other half of the calendar. Our posted hours are Monday to Thursday 6:00 AM to 3:00 PM and Friday 6:00 AM to 2:00 PM, which is a summer trenching schedule more than an office one. If the site has a noise restriction blocking a 6:00 AM start, say so at bid time; it changes production rates. Above grade, dust matters as much as rain: NEMA Type 3R is rainproof and carries no windblown-dust requirement at all, while Type 4 is built to keep it out. For pull boxes, pedestals and pole bases, 3R is often the wrong default.
Licenses, the right-of-way, and where we stop
The license classification decides where an electrical contractor's underground scope ends, and most GCs have never read the language. The ROC scope for a C-11 or CR-11 covers "all underground electrical distribution systems of less than 600 volts serving private properties," and covers outside and underground construction only "on other than public right-of-ways." Read plainly: a CR-11-only contractor stops at the property line, and at 600 volts.
We hold KA Dual Engineering, ROC 312437 alongside CR-11 Electrical, ROC 276948 and KB-1 Dual Building Contractor, ROC 329360. The engineering license is what lets us carry the heavy civil and the right-of-way work instead of subbing it out and coordinating around someone else's crew. All three are active and state-issued, valid in every Arizona county. Check them yourself.
Jurisdiction still matters, because Arizona has no statewide building code — every municipality adopts and amends independently. Phoenix has enforced the 2023 NEC since 1 August 2025 under Ordinance G-7397; unincorporated Maricopa County is still on the 2017 NEC, and county islands are exactly where underground work lands.
What we will not do
- Energize anything on the utility side. Nor can anyone who is not an APS or SRP employee, whatever the schedule says.
- Take unclassified excavation on a lump sum with no geotechnical data and no rock clause. Ask for it that way and you get an exclusion instead.
- Treat restoration as an afterthought. Pavement replacement in a public street is its own permit, detail and inspection.
- A single short service trench. This page is site-scale underground: duct banks, primary, and the civil that comes with a new service.
- Promise a utility energization date. APS and SRP schedule their own crews.
Send plans, specifications, the civil set and any utility correspondence through the contact page. If the service is not designed yet, this scope usually belongs in design-build — utility coordination is the long pole, and it starts on day one instead of after the drawings are done.
Frequently asked questions
Do you trench, or do we need a separate civil contractor?
We self-perform it. The company holds a KA Dual Engineering license and a KB-1 Dual Building Contractor license alongside the CR-11 electrical license, and we run our own excavators, trenchers and operators. On most jobs that means the trench, the duct bank, the transformer pad, the conduit, the backfill and the restoration are one scope under one contract, so the coordination happens inside our office instead of in your weekly meeting.
Who calls Arizona 811, and how far ahead?
We do, for our own excavation. Arizona 811, which most people in the field still call Blue Stake, must be notified before digging, and APS requires contact at least three days before excavation. Build that into the look-ahead rather than treating it as a same-week phone call. Also remember the ticket locates member facilities in the public system only. Private irrigation, site lighting circuits, fiber between buildings and abandoned conduit on private property are not on it, which is why we price a potholing allowance on a developed site.
How deep does the conduit have to be?
It depends on the wiring method and on what sits above the trench. NEC Table 300.5(A) sets 24 inches of cover for direct burial and 18 inches for PVC listed for direct burial in ordinary locations, but everything under a street, driveway or parking lot goes to 24 inches regardless of method. The utility service lateral is a separate question, because installations under the exclusive control of an electric utility fall outside the scope of the NEC under Article 90.2. That trench detail comes from the APS Electric Service Requirements Manual or the SRP Electric Service Specifications.
What happens if the trench is backfilled before the utility inspects it?
You open it again. SRP states it directly in its underground service specifications: trenching and conduit must be inspected prior to backfill, and the service lateral is installed only after both SRP and the authority having jurisdiction approve the installation. APS runs the same sequence, inspecting the trench and then the conduit and equipment pads before its crews are scheduled. Closing a trench early is the most expensive shortcut on an underground job.
How do you handle caliche and rock?
Contractually, before the shovel goes in the ground. Caliche is cemented hardpan, so it changes production rates rather than the design. We want the geotechnical report if one exists, and where there is none we carry a unit price for unclassified excavation and write our subsurface assumption into the proposal. The other half is backfill: NEC 300.5(F) does not allow large rocks or sharply angular material to be placed where it could damage the raceway, so broken caliche generally leaves the site and select bedding comes in. Both the haul-off and the import are line items.
Can you work in the public right-of-way?
Yes. The ROC scope of work for a C-11 or CR-11 electrical license covers underground distribution serving private property and limits outside and underground construction to other than public rights-of-way, so an electrical-only contractor has to stop at the property line. We hold KA Dual Engineering, ROC 312437, which covers the engineering and right-of-way scope, in addition to the CR-11 electrical license. Tell us at bid time what the agency requires for bonding, traffic control and restoration so it is priced rather than discovered.
How long after backfill before APS or SRP energizes?
That is the utility's schedule rather than ours, and any contractor quoting you a firm date is guessing. The sequence itself is fixed: the utility approves the design and the service entrance drawings, inspects the trench and conduit before backfill, releases the job to its own construction crews, inspects the meter panel, and energizes only once the city or county electrical clearance is in hand. What you can control is starting the utility application early and not failing an inspection. Both utilities revise their standards often. SRP logged six changes to its service specifications between April and August 2026, so we work from the current published version on every job.
Get a price on this scope
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