Typical facilities include retention basins, infiltration basins and percolation trenches. Stochastic block models exhibit a sharp threshold effect reminiscent of percolation thresholds. The water percolation in alkali soils is very poor leading to waterlogging problems. Hash oil is produced by solvent extraction (maceration, infusion or percolation) of marijuana or hashish. Flowstones are formed via the degassing of vadose percolation waters. Directed percolation can be also regarded as anisotropic percolation. The conjecture was proved in the special case of site percolation on the triangular lattice. The structural robustness of networks is studied using percolation theory. Combinatorics is commonly employed to study percolation thresholds. Polyominoes have been used as models of branched polymers and of percolation clusters. Site bond percolation (both thresholds apply simultaneously to one system). In percolation theory, random fuse networks have been studied. Observations can describe features caused by wind, water percolation, or snow unloading from trees. This article deals with the critical exponents of random percolation. The failures discussed above are random, as usually assumed in percolation theory.