250.70 Methods of Grounding and Bonding Conductor
Connection to Electrodes. The grounding or bonding conductor
shall be connected to the grounding electrode by
exothermic welding, listed lugs, listed pressure connectors,
listed clamps, or other listed means. Connections depending
on solder shall not be used. Ground clamps shall be
listed for the materials of the grounding electrode and the
grounding electrode conductor and, where used on pipe,
rod, or other buried electrodes, shall also be listed for direct
soil burial or concrete encasement. Not more than one conductor
shall be connected to the grounding electrode by a
single clamp or fitting unless the clamp or fitting is listed
for multiple conductors. One of the following methods
shall be used:
(1) A pipe fitting, pipe plug, or other approved device
screwed into a pipe or pipe fitting
(2) A listed bolted clamp of cast bronze or brass, or plain
or malleable iron
(3) For indoor communications purposes only, a listed sheet
metal strap-type ground clamp having a rigid metal base
that seats on the electrode and having a strap of such
material and dimensions that it is not likely to stretch
during or after installation
(4) An equally substantial approved means