  We study the abelian sandpile model on the upper half plane, and reconsider
the correlations of the four height variables lying on the boundary. For more
convenience, we carry out the analysis in the dissipative (massive) extension
of the model and identify the boundary scaling fields corresponding to the four
heights. We find that they all can be accounted for by the massive pertubation
of a c=-2 logarithmic conformal field theory.
