What does the marking mean?

If it's part of the easement then there is very little you can do.

I looked at the plot map, no easement on this side. Still curious what it means…

I would be surprised if there is not an easement...

 General will be one several feet (15 to 25 feet) from edge of road or alley.

Check with local county office and online for utility easement in state or city.... electric, gas, water, sewer, communication all operate in the same easement.

According to Google, white is for excavation/boring. Which I didn't know. 

To my knowledge white is for proposed route, as paint and flags are only used for ground services, boring/excavation would be the expected method.

As a quick refresh, the APWA color code for utility marking is:

• Red: electric power lines, cables, conduit and lighting cables
• Orange: telecommunication, alarm or signal lines, cables or conduit
• Yellow: natural gas, oil, steam, petroleum or other flammable
• Green: sewers and drain lines
• Blue: potable drinking water
• Purple: reclaimed water, irrigation and slurry lines
• Pink: temporary survey markings, unknown/unidentified facilities
• White: proposed excavation limits or routes

Worried it indicates they are installing fiber and will be tearing up my trees and beloved garden.

Are there any other areas marked beyond that corner turn? If it is AT&T Fiber they are not going to impact your trees or garden unless they are planted in the Utility Easement.

Dave

I found a square painted in the backyard that is in the easement. Yes there is some easement along the street, but not along the side of my property to the back fence. I have the plot maps. I think it might be letting them know where to dig in the back easement which I am fine with because it is just a chicken coop.

Still wondering what Lazer means??

This is just a guess, but I'd say to use a laser to bore under the surface to get a straight shot. To keep the boring rod straight.