I'm a young engineer and new poster so you'll have to forgive my inexperience. I'm dealing with a project that requires distributing 5kV service lines across a campus as well as stepped down voltage (120V/208Y & 277V/480Y) distribution to certain facilities. In order to save space and lower cost, I was thinking about running the 5kV and the lower voltage lines in the same trench. From my understanding of the NEC 300.3(C) there is no recommendation against doing this. Furthermore, combing the values from table 300.5 & 300.50 (Minimum cover requirements for 0-600V & above 600V respectively), the lower voltage line requires 18in. minimum while the 5kV line requires a 30in. minimum cover spacing for direct burial, resulting in 12in. seperation between the conductors of different systems. Am I correct to assume that the code allows for this practice?