PG&E Joint Trench Process: The Compliance Baseline
You can’t break ground on any California development without coordinating with PG&E on underground utility placement, and that coordination starts with understanding the joint trench process. I’ve managed dozens of projects where developers thought they could design their utility runs independently, then call PG&E for approval—that approach costs time and money. The joint trench process isn’t optional; it’s mandated under California Code of Regulations Title 8, Section 5597, and PG&E’s own General Order 128-B, which governs underground service installation.
What Is a Joint Trench and Why It Matters
A joint trench is a single excavation that carries multiple utility lines—typically gas, electric, and communications—in a shared corridor. PG&E encourages joint trenches to minimize ground disturbance, reduce conflicts, and consolidate permitting. In my experience, developers who plan for joint trenches early see faster approvals and lower construction costs than those fighting for separate utility corridors later.
The key benefit is spatial efficiency. On a tight urban lot in Oakland or San Francisco, a joint trench reduces the footprint needed for utility runs by up to 40% compared to separate trenches. But here’s what catches people off guard: the process requires alignment between your design engineer, PG&E’s service planning team, and any other utility providers (water, sewer, telecom) weeks before excavation begins.
Initial Coordination: Submitting the Utility Plan
Your first step is submitting a detailed utility coordination plan to PG&E’s Service Planning department, not just calling a local office. The plan must include:
- Site survey with existing utility locations marked (call 811 for the location ticket first)
- Proposed trench depth and alignment, dimensioned on civil plans
- Separation distances between gas and electric lines (minimum 12 inches horizontal per GO 128-B)
- Conduit specifications and protection methods for underground service
- Load calculations if you’re requesting new service capacity
We’ve found that PG&E typically responds to initial submissions within 10–15 business days, but only if the submission’s complete. Missing load data or vague trench routing triggers a request for clarification that adds another two weeks. Submit early—30 to 45 days before your target construction start date.
Minimum Separations and Clearance Requirements
California’s code doesn’t leave spacing to guesswork. PG&E’s General Order 128-B and the California Title 24 Energy Standards mandate specific clearances. Gas and electric lines need at least 12 inches of horizontal separation within a joint trench. If you’re installing conduit for future service, that conduit must be fiberglass or plastic, not metallic, to prevent electromagnetic interference with electric lines.
Vertical stacking is allowed—gas on top, electric below—but requires a barrier or minimum 6 inches of compacted material between them. In my projects, we’ve learned to over-specify protection: cable trays, concrete encasement, or PVC-wrapped bundles. It costs a bit more upfront but eliminates field disputes and change orders when PG&E’s inspector shows up.
If your site crosses under a structure (foundation, driveway, building slab), minimum burial depth for combined underground service is 36 inches under buildings and 24 inches under pavement per GO 128-B. You’ll need concrete encasement or rigid conduit in those zones—plan for it in your excavation sequencing.
Permitting and PG&E Approval Letter
PG&E doesn’t issue a traditional permit the way a city does. Instead, they issue a Service Design and Layout (SDL) letter once they’ve reviewed your utility plan and confirmed feasibility. This letter authorizes your contractor to work in PG&E’s right-of-way and specifies their inspection points.
You’ll need this SDL letter attached to your local building permit application. Most city departments in the Bay Area and Central Valley won’t issue a grading or building permit without proof of PG&E coordination. We include the SDL letter in Appendix C of every set of civil drawings we submit to cities. If you’re working in an unincorporated area, your county’s engineer still requires it.
PG&E’s approval is contingent on your plans meeting General Order 128-B standards, which are stricter than many developers expect. They’ll reject trenches that don’t provide adequate clearance for future maintenance access, even if the immediate installation fits. Plan for 3 to 4 feet of accessible trench width on PG&E utility runs.
Construction Phase Coordination and Inspections
Once you’ve got the SDL letter and your city permit, PG&E requires at least 48 hours’ notice before you start excavation near their utility lines. Your contractor must call the local PG&E field office and your project engineer to schedule a pre-excavation walk-through. I always attend these—miscommunication in the field is where delays happen.
Expect PG&E to have an inspector present during trench opening and utility placement. They’ll verify burial depth, separation distances, and conduit integrity before you backfill. If anything doesn’t match the SDL letter, they’ll issue a notice of non-compliance, which means you don’t backfill until it’s corrected. That’s a two-day delay minimum if your contractor’s experienced; longer if they’re not.
Your contractor must also obtain a PG&E work ticket (separate from the SDL letter) for any live utility work. This is standard on sites where existing service is active nearby. The ticket authorizes PG&E’s field crew to de-energize lines or isolate gas pressure if needed during excavation.
Common Pitfalls and How to Avoid Them
The biggest mistake I see is underestimating the timeline. Developers often schedule construction before PG&E coordination is done, hoping to fast-track. It doesn’t work. PG&E’s Service Planning process takes 30–60 days minimum in urban areas, longer in rural regions where their crews have fewer resources.
Second: not calling 811 for existing utility location before design. You’ll design a trench, PG&E will flag it crosses an unmarked line, and now you’re redesigning mid-project. Call 811 the moment you own the property and have a preliminary site plan ready.
Third: assuming standard residential trench depth works for commercial or industrial service. Commercial loads require deeper burial and heavier-duty conduit. We’ve seen projects stall because the developer specified residential-grade installation, then PG&E’s engineer flagged it for upgrade during the SDL review.
Work With an Engineering Firm That Handles PG&E Coordination
This process works smoothly when your civil engineer manages it from day one. We submit utility coordination plans as part of our civil engineering services, and we include PG&E pre-approval timelines in our project schedules. We’ve also developed a coordination template that accelerates PG&E’s review process—it’s become standard in our East Bay projects.
If you’re planning a development in California, don’t treat PG&E coordination as an afterthought. Build it into your design schedule, submit early, and use a team that knows General Order 128-B inside out. It’ll save you weeks and real money on utilities. Contact Calichi Design Group if you need guidance on PG&E coordination for your next project.