Trenching

The customer is responsible for all digging/backfilling the electric service trench. The following requirements are needed prior to the PUD energizing service:

• Customer is responsible for digging up to the PUD source (i.e. pole, transformer, pedestal, junction box, etc). PUD crew not responsible for digging the final portion of the trench.
• Trencher/ditch witch is not acceptable.
• Any trenching done within a public right-of-way, on property not owned by the customer, or the project requires exposing an existing underground line, only a PUD approved licensed and bonded contractor, hired by the customer, may perform work and must adhere to standards of the local jurisdiction.
• Trench must be 36” to 48” deep, measured from surface to top of conduit, by 18” wide. Any turns/bends in the trench will require a 24” trench width. See table on following page for minimum trench depth based on conduit size.
• Trenching to the back of the transformer is not accepted. See following page for transformer trenching diagram.
• Customer must trench all the way flush with the utility pole (if applicable).
• Trench shall be as straight as possible.
• PUD installed conduit run shall have no more than three (3) 90-degree bends (270 degrees) of which no individual bend is less than a 36-inch radius. This total includes the elbow into the source facility.
• Trench shall be free of trash and be thoroughly compacted throughout.
• Native backfill with large rocks, paving materials, cinders, large or sharply angular substance, or corrosive material shall not be placed back into the trench.
• Contact Skamania PUD once the trench is open. Trenching should only be done after electrical inspection is approved and the meter base, riser conduit and the 36-inch radius sweep have been installed.
• Schedule the trenching so it’s open for the shortest time to avoid creating a public hazard and minimize possible trench collapsing.
• If a junction box or padmount transformer is installed, customer is responsible for putting down a gravel pad using either 5/8” or 3/4” minus gravel compacted down. See the following pages for dimensions.

Trenching Diagram

Note: Customer-owned electric services on the customer (load) side of the meter fall under the jurisdiction of the Washington State Department of Labor and Industries. It is the customer’s responsibility to adhere to each governing body’s specifications in regards to trenching, conduit, wire, etc.

Transformer Trenching Diagram

Gavel Pad Diagram

Single Phase Transformer

Three Phase Transformer

Single Phase Junction Box

Three Phase Junction Box