  The variation of z in BTW model in presence of holes (dissipative sites) has
been studied. The value of z decreases as the fraction of number of holes
increases. Interstingly, it is observed that the variation of the rate of
change of z with the fraction of number of holes is different for the two
different types of distribution of holes over the lattice. When the holes are
randomly distributed over the lattice then the dissipation is more compared to
that of the case when the holes are present in the form of a single compact
cluster with same fraction. The value of z is less in the first case than that
observed in the second case.
