URD and Gas Distribution

Urban gas distribution systems are necessarily associated with any other utility using underground space in streets, alleys or easements. Each service or supply crossing represents a potential hazard to either cathodic protection systems or damage to the pipe whether it be plastic or metal during the utility installation phase of construction. For the plastic system of City Public Service Board, we experienced four construction penetrations during the construction phase on 20, 000 feet of mains and services. No trouble has been reported since the installation phase was finished. Should there be an electric URD cable failure in the vicinity of the plastic pipe, then a possible penetration could occur but this situation should be very rare. Of more immediate concern would be a dig-in, penetrating both URD cable and plastic gas pipe, producing a fire from the gas and the electric arc. Hope fully, with future planning developed as well as it is in most metropolitan areas, the dig-in should become rare. In areas where development is slow or spotty, this may very well be a problem. For coated metal pipe, such a dig-in may produce a voltage surge on the gas pipe. Again, relay settings breakers or fusing should trip out the URD cable before any voltage surge becomes significant. We ask ourselves, "is this adequate?", and the answer comes back, "it should be", but situation experience is absent at this point. Experience to date reports no fatalities nation-wide associated with URD cables.