  We use SLE(6) paths to construct a process of continuum nonsimple loops in
the plane and prove that this process coincides with the full continuum scaling
limit of 2D critical site percolation on the triangular lattice -- that is, the
scaling limit of the set of all interfaces between different clusters. Some
properties of the loop process, including conformal invariance, are also
proved. In the main body of the paper these results are proved while assuming,
as argued by Schramm and Smirnov, that the percolation exploration path
converges in distribution to the trace of chordal SLE(6). Then, in a lengthy
appendix, a detailed proof is provided for this convergence to SLE(6), which
itself relies on Smirnov's result that crossing probabilities converge to
Cardy's formula.
