  The Abelian Sandpile Model (ASM) is a paradigm of self-organized criticality
(SOC) which is related to $c=-2$ conformal field theory. The conformal fields
corresponding to some height clusters have been suggested before. Here we
derive the first corrections to such fields, in a field theoretical approach,
when the lattice parameter is non-vanishing and consider them in the presence
of a boundary.
