Attach a clamp to base of mast and use 6 guage copper wire run all the way to the electric company ground rod location and clamp it to that using your own clamp (do not loosen electric company ground wire). Then on the coax run put in a ground block which also bonds to that same ground rod location. This way there are no grounds with a difference of potential.
It's not a good idea to have a long ground wire between the antenna mast and the common point
of the electrical meter ground. The NEC (National Electrical Code) provides for a common bonding
of telecommunications equipment grounding system to the electrical service ground. It does not
suggest or even imply that this should be the only source of earth ground for the equipment.
You would be much better off to provide your own ground rodS to ground your mast before going
to the meter service ground. You notice that I used the plural term of multiple ground rods. The
chances of getting a good low resistance earth ground with only one ground rod is rather low.
So you would be better off with multiple ground rods spaced at an interval of twice their length.
What this means is that if you are using 8 foot ground rods, you space them 16 feet apart.
You can use the distance between the electrical meter and your antenna mast for the ground
rod spacing. It will do no good to drive the ground rods closer together. The cone of influence
is where the spacing comes from. If you space the rods closer, the cone of influence from
each of the rods will overlap and reduce the effective low resistance gained by the multiple rods.
Another reason to space the rods is to allow for the high current dissipation if you ever take a hit.
The soil around a ground rod will have a tendanancy to turn to glass trying to get rid of the high
current. If the rods are spaced to the max extent of the cone of influence, the ground has a better
chance to absorb the high current from a strike and be able to dissipate it easier and faster.
Jim