Thank You for all of your suggestions.
I got my brother's digital camera and will document tomorrow.
A couple of things...
The neighbor said he saw a green city truck with the city of Oakland official seal on the door on my trail. The city of Oakland is responsible for all public sewers in the city. Many times over the years I have reported thousands of gallons per hour raw sewage spilling into the area creeks that have gone on for days and even weeks. Often I have to show the city where their pipe is leaking. All of the Oldtimers have retired and the new guys are truely lost when they have to fix a problem on raw land.
In the dirt,at my trail, I found a 5 1/2 by 8 1/2 official notice form from the city stating they need access to my backyard and to call the office between 8:30 and 4:30. The notice was not dated, was not signed nor was it left at my home.
The trail only serves my land, it does not connect to adjoining parcels. To do so would required bridging 3 creeks.
The city has a well documented through easement over their sewer main. The problem is the city has not maintained their easement and in some places it is covered by a walls of Poison Oak. They have no access from my trail.
This is the first time, going back to 1977, (the year I put up the chain at the request of the Fire Dept.) that anyone besides me has driven on my trail. I have the only key and I keep it on my key ring.
The tree situation in Oakland has become such a big deal that God help anyone that damages a tree, especially Oak Trees. I had to get a $50 dollar permit to take out a dying walnut tree in my own backyard.
Before the permit was granted, the utility poles in the area had to be posted and I had to wait 4 weeks to allow time for public comment. I guess the rules don't apply if you are the one who makes the rules.
In the scope of things, the damage is small... I know my canopy of huge oak limbs shading the trail will not come back in my lifetime. After thinking about it, I would say the total disrespect for private property that has me ticked.
Side note, an attorney acquaintance of my brother has cautioned that I may not want to make a big deal out of this because the city always has the option of condemnation.
Over the years, owning acerage in this city seems to be more trouble than it is worth. The neighbors all think it is open space parkland, the fire department requires I maintain fire breaks, not to mention the weed abatement folks, visits from code compliance from illegal trash dumping, etc.