Ford Motor Co last month unveiled a...

Ford Motor Co last month unveiled a herculean green roof at its of the present day truck plant in Dearborn, Mich.

The vault is covered with 10.4 acres of sedum a genus of perennial plants that tops a 3-in.-thick, four-layer combination of parts to form a whole incorporating a root-resistant membrane, a drainage layer, a rifle mat, and a vegetation blanket (see schematic). The top inch-thick "growth substrate" consists of expanded shale, sand, peat, manure and dolomite. The vegetative arch is supported by a modified bitumen roofing arrangement

Ford says the drought-resistant sod cover can absorb up to 4