  (abridged) We have analyzed the properties of the Na D doublet lines in a
large sample of 691 radio galaxies using the Sloan Digital Sky Survey (SDSS).
These radio galaxies are resolved in the FIRST survey, have redshifts less that
0.2 and radio flux densities at 1.4 GHz higher than 40 mJy. Approximately 1/3
of the sources show a significant excess (above that contributed by their
stellar populations) of Na D absorption that can be robustly fitted with two
Voigt profiles representing the Na D doublet. A further 1/6 of the sources show
residual absorption, for which the fits were not well constrained though while
~50% of the sample show no significant residual absorption. The residual
absorption is modestly blueshifted, typically by ~50 km/s, but the velocity
dispersions are high, generally ~500 km/s. Assuming that the size of the
absorbing region is consistent with ~1 kpc for dust lanes in a sample of
generally more powerful radio sources and a continuous constant velocity flow
(continuity equation), we estimate mass and energy outflow rates of about 10
Msun/yr and few x e42 erg/s. These rates are consistent with those in the
literature based on HI absorption line observations of radio galaxies. The
energy required to power these outflows is on the order of 1-10% of the jet
mechanical power and we conclude that the radio jet alone is sufficient. The
mass and energy outflow rates are consistent with what is needed to heat/expel
the mass returned by the stellar populations as well as the likely amount of
gas from a cooling halo. This suggests that radio-loud AGN play a key role in
energizing the outflow/heating phase of the feedback cycle. The deposition of
the jet mechanical energy could be important for explaining the ensemble
characteristics of massive early type galaxies in the local universe.
