Aerial cable connections - clearances required

[winslowfam]

hi...our client needs a 480 volt feeder from their main plant building to a rack-mounted panelboard that will provide power for local various loads. The feeder to this new panelboard will be installed from a service mast/head on the outside wall of the building to a new pole located next to the new panelboard, 100 feet away, with another service head at the rack. The space between the building and the panelboard is an un-used open field, with no activity or build-up ever planned for that area. I am having a hard time figuring out how much clearance above grade is required for this feeder at each end, and how high the service heads need to be at each end.

 

[Volta]

I think your answer for the span height is in sub-section (4):

225.18 Clearance for Overhead Conductors and Cables.
Overhead spans of open conductors and open multiconductor
cables of not over 600 volts, nominal, shall have a
clearance of not less than the following:
(1) 3.0 m (10 ft) - above finished grade, sidewalks, or
from any platform or projection from which they might
be reached where the voltage does not exceed 150 volts
to ground and accessible to pedestrians only
(2) 3.7 m (12 ft) - over residential property and driveways,
and those commercial areas not subject to truck
traffic where the voltage does not exceed 300 volts to
ground
(3) 4.5 m (15 ft) - for those areas listed in the 3.7-m (12-ft)
classification where the voltage exceeds 300 volts to
ground
(4) 5.5 m (18 ft) - over public streets, alleys, roads, parking
areas subject to truck traffic, driveways on other than residential
property, and other land traversed by vehicles,
such as cultivated, grazing, forest, and orchard
(5) 7.5 m (24.5 ft) - over track rails of railroads