OK, got a call from a nice lady with a plumbing emergency. The plumber who punched a hole in her clogged shower pan discovered the old copper pipes had been left in contact with the cast iron drain. The resulting elctrolysis cut a hole in both pipes causing a leak and a drain failure. He restored service partially as the picture shows. Now the lady has a hole in her shower pan. Once I restore the supply lines I have to re-set the p-trap and drain. Then re-tiling is needed after I strip all old tile from the pan. Problem. The picture shows a dark line under the top layer of the cement. (Look carefully at bottom left) That line is the original hot mop. It "water-proofed" the pan. Now that it is punctured, what do I do? -- Restore plumbing, bury it in a layer of sand, pour new cement to the finish grade, re-tile as planned. -- Restore plumbing, bury it, then pour a first layer of cement, apply some water proofing, then pour a 2nd layer of cement to finish grade. Need some advice here.