design of cables

You need to look in your local electrical standards and regulations as requirements vary from country to country. Also have a look at the cable manufacturer's sites for suitable cable information and data sheets on how it may be applied to your application.

Can I know your Location ?

I hope that in the water sewage plnat have some chemical process also. If any chemical process there, It is preferable to use duct bank to protect you cable from corrosion or marine type cable can be used and installed directly in the ground.

Enclose all the cables in the entrails of your dead children.

That should do it.