The U.S. Environmental Protection Agency has given preliminary approval to a request by the Coaldale-Lansford-Summit Hill Joint Sewer Authority to use filtered sludge from its system for the planned Blue Mountain vegetation project. Ronald Tirpak, of Carbon Engineering Inc., engineer for the authority, said the EPA has looked favorably upon the authority's plea. The EPA has discussed utilizing sludge from the Panther Valley towns as well as from Allentown, Philadelphia, and Palmerton to revegetate it.