Opinion needed here from a Sparky

[sparks]

http://www.nachi.org/forum/showpost....58&postcount=1

http://www.nachi.org/forum/showthrea...7919#post47919

[Greg Fretwell]

If you haven't started yet you could put 20' or more of #4 (or larger) rebar in the footer. Use a concrete listed clamp to attach a 250.66 sized conductor as your GEC. (typically a #4 solid). Attach this with a lug to building steel and a listed clamp to the piping system to complete the system

[Paul W. Abernathy]

(3) Concrete-Encased Electrode.

An electrode encased
by at least 50 mm (2 in.) of concrete, located within and
near the bottom of a concrete foundation or footing that is
in direct contact with the earth, consisting of at least 6.0 m
(20 ft) of one or more bare or zinc galvanized or other
electrically conductive coated steel reinforcing bars or rods
of not less than 13 mm (½ in.) in diameter, or consisting of
at least 6.0 m (20 ft) of bare copper conductor not smaller
than 4 AWG. Reinforcing bars shall be permitted to be
bonded together by the usual steel tie wires or other effective
means.

Just some additional code verbage for ya.......Greg is right on top of it and perfectly correct as usual......