Underground Conduit Spacing for 2 - 15kv Conduits

[gjabei]

I cannot find the NEC underground spacing requirements for 2 - 15kv Feeder Conduits (5")with 3/C # 500 MCM Cable in each conduit.

 

[RUWired]

Perhaps figure 310.60 (page 70-166) 2014 edition would be useful.