Some projects can have miles of underground conduit while others may have very little.

A free-standing new building such as a car dealership will have much underground conduit supplying parking lot lighting, other detached buildings, and monument signs. A remodel to turn an existing business office into a dental office might not involve new underground conduits outside the building envelope, but it will likely require concrete slab cutting and underground conduits installed to each location where a dental exam chair will be placed inside the building.

Make sure to examine construction timelines to know when the general contractor plans to have site work and paving completed. If there will be parking lot lighting installed, be sure to follow the plans for the lighting pole base diagrams. For parking lot lighting, getting the conduits installed and ready for inspection will take some coordination if other trades are setting the form and installing the rebar. Often, the electrician is responsible for all aspects of the pole base installation including drilling the hole to the proper depth, setting the form, installing rebar (where required) and installing the electrical conduits.

Many jurisdictions will have combination inspectors who will expect to see the entire pole base as well as the electrical conduit and any required grounding ready to go for a single inspection. The inspector wants to be called out for inspection of the pole bases when everything is 100% installed and ready, but just before the concrete is poured.

Be mindful of any additional grounding specified by the electrical engineer. The NEC^® does not specifically require ground rods or a grounding electrode conductor to be installed inside a light pole base, but many engineers show them on the plans as an additional measure that is above the minimum code requirements.

When the inspector arrives to inspect the pole bases, the following should be done:

• Underground conduit type and size per plan, installed at proper depth (at least 24 inches to top of conduit per NEC^® Table 300.5)
• Pole base hole drilled to match the diameter and depth shown on the plans
• Form tube installed with conduits stubbed up into the pole base at appropriate location
• Rebar cage (if required) in place and matching the design specification for size of rebar, number and spacing of horizontal rebar rings as well as vertical rebar rods
• Rebar cage inside the form tube is not in contact with the earth and has at least 3 inches clearance to the wall of the form tube to ensure full concrete encasement
• Grounding installed as specified and clamped to rebar cage with clamp listed for the purpose