Any Advice For Burying Conduit?

At the minimum call 811 before you dig anywhere, especially 36" below ground, and if you're not going to hire someone to trench and install the conduit, rent a ditch witch for ~$300 for the day. There's no way it's worth it to dig those by hand.

I'd rent a trencher for a couple hundred dollars for a day before planning to spend two or three days hand digging a trench.

One of those walk-behind trenchers will still take a whole day to make three cuts if they are 36" deep.

Also, consider using galvanized steel conduit rather than PVC.  Even Sch 40 seems to get brittle and break when the ground moves, like under a road bed.

811 first and always. 

Can the work be included in contractor's scope of work?  A backhoe will do the trick, if the contractor has one on site.  If you steer people away from DIY security installs why would you not take your own advice and hire someone to do it right the first time.  (Rent a bobcat with a hoe if you have to do it yourself)

We run 4" conduit in groups of 2/4/6/8 lately, used to be 2" but we found the cost of 4 over 2 was worth it on long pulls.  As it is a roadway with trailers, I'd suggest pouring concrete to hold the conduit in place, too...it can get costly but you'll be set for a long time.

Stub up to boxes on both sides of the road and you've made future work less disruptive and less expensive.

There is so much more to this if it’s a public road.

Physically putting a pipe in the ground isn’t rocket science.  I would look at local engineering bid plans by the public traffic, water or sewer agency if you want to know how deep, what packing, what materials etc.  That’s the cheap way to learn.  

The ditchwitch idea...golden and at 3’ I would use the walk behind or riding tractor type.  I like my back.

Obviously 811 for dig marking, IF they will mark for you across a public road you don’t own or have a permit for.   You might be surprised what is under a road that people don’t know about.

In California, above or underground, legally you have to pay a monthly lease fee to cross a public road because the “right of way” is owned.

I'd probably take your planning a bit further and try to run the conduit closer to actual desired end points on both sides, particularly if you are going to be renting equipment for the job.

At a minimum, you should probably run 2 conduits with a bit of separate, 1 for high voltage, 1 for low voltage.

What are you going to do with the end points? If you leave them stubbed up above ground they are likely to get damaged by grounds maintenance over time. Plus they become possible trip hazards and just look unsightly. If you bury them underground, make sure you have some way to locate the ends in the future. Placing a large bolt or thick metal plate on top of the ends would make them easy to find with a metal detector later.

I'd probably run a conduit pair over to that top-right corner in your image too, not sure if that will cause more disruption in the overall project.

At 3ft you will need to compact the soil when backfilling or the road will sink over time.

What everyone else said...

and install handholes at each end. Quazite or New Basis type.

If they are milling the road, that is only the top layer. You will still have asphalt to deal with, that you will have to cut.

It looks like you still have to get to the back corner grassy area which is a lengthy bore.

If you have an installer involved, I suggest you have them involved because the last thing you want is to do this work, then have the integrator say it wasn't right or how they would have designed it.