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Can Water and Electric Lines Share a Trench?

In PG&E territory, a water line does not go in the joint trench. PG&E’s joint trench guide lists the occupants it allows: gas, electric (primary and secondary), telephone, cable TV and streetlights. It says non-utility facilities, such as irrigation control lines and private wiring, are not allowed in any joint trench, and it treats water as a “wet” utility to be kept apart from PG&E’s dry facilities.

How Far Apart Do Water and Electric Need to Be?

PG&E’s guide sets the minimum horizontal separation between its facilities and wet utilities at 3 feet, with at least 1 foot of undisturbed earth or a suitable barrier between them. If 3 feet can’t be reached, PG&E can approve a variance, and it may waive the minimum on a written request that justifies the need. Separations of 1 foot or less are not permitted (PG&E S5453, Exhibit B, General Note 9).

What the Water Agency Adds

In East Bay Municipal Utility District’s service area, water mains must keep at least 1 foot vertically and 5 feet horizontally from other utilities, sit 7 feet from the face of curb, and have 36 inches of cover to final grade. EBMUD also warns that joint trenches that conflict with its criteria may delay the project, and it asks for final joint trench plans, not intent plans, showing the trench size and the utilities in it.

Other water agencies set their own criteria. Get the district’s current standard before the trench detail goes on the plans.

Water and Sewer Are a Separate Question

For public water mains, California’s drinking water regulation says new water mains and supply lines may not be installed in the same trench as a parallel pipeline carrying untreated or treated sewage, certain recycled water, or hazardous fluids. They must be at least 10 feet horizontally from, and 1 foot above, such a pipeline. A crossing must be at 45 degrees or more and 1 foot above, with no joints within 8 horizontal feet (22 CCR §64572).

For private plumbing, the California Plumbing Code allows a water pipe in the same trench as a building sewer made of clay or other materials not approved inside a building only if the water pipe is at least 12 inches above the sewer, on a solid shelf at least 12 inches to the side (CPC 609.2).

What This Means on a Project

Start with the utility’s current standard and the water agency’s design criteria, then show the separations on the composite utility plan. If you’re planning a dry utility layout, see our joint trench design work, or read our guide to the PG&E Green Book.

Sources

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