Gut reaction:Get the people out of the video.More lighting, slower camera movementDon't do a video at night!

Electricity for lights, secured to the containers(to save $), video camera surveillance,  fence (although some places I've seen have no fence, I've noticed) and electric gate, signs, the containers themselves. 

Just try to invest in good cameras?

No mailed check or pick ups.Purchase price 300k and owner is giving 20k towards upgrades/repairs etc Plan is to install surveillance cameras, lights, paint doors and shutters, 2 water heaters and new signage and minor fixes etc.

You could also try security camera to see who is dumping.

It uses AR tech on your iPad to estimate distances by the gyroscope and camera in your device and is pretty much licensed as the engine for most of the other AR floorplan apps on the store. 

It is as well in a gated community and very secure with cameras at the main entrance...

Install security system and cameras.

Once I'm done with the forums related to duck hunting, shotgun reloading, MIG welding, heavy equipment work (dozer & skidsteer) and weightlifting; I go to this forum for STRs.I mainly like to share my horror stories...someone overdosing, entering a vacant STR when there is an intruder inside, watching another intruder break in a house live on a security camera, tenants having affairs with other tenants spouses, disconnecting utilities to encourage problem tenants to leave, etc.

Chances are wherever the payments were cashed there's video surveillance.