LACLEDE GAS CO

Incident Narrative

A 2-INCH STEEL NATURAL GAS MAIN WAS EXPOSED IN AN EXCAVATION BY A CONTRACTOR PREPARING TO INSTALL A WATER MAIN ON DECEMBER 16, 2009 . THE 2-INCH LINE WAS CONNECTED TO A 2-INCH VALVE JUST BEYOND THE EXCAVATION. THE EXCAVATION WAS QUICKLY BACKFILLED THE SAME DAY IT WAS EXCAVATED. IN THE DAYS FOLLOWING THE BACKFILL, HEAVY RAIN SATURATED THE AREA AND FILLED THE VOIDS CREATED BY THE RECENT EXCAVATION WITH MOISTURE. THIS WAS QUICKLY FOLLOWED BY EXTREMELY COLD TEMPERATURES. A LEAK WAS REEORTED BY THE PUBLIC IN THE AREA OF THE DECEMBER 16 EXCAVATION, ON JANUARY 12, 2010. DURING REPAIR THE MAIN REMAINED ACTIVE IN ORDER TO MAINTAIN SERVICE TO CUSTOMERS. ON JANUARY 13, 2010, IT WAS ESTIMATED THAT THE COST OF REPAIR AND THE RELEASED NATURAL GAS WOULD EXCEED $50,000. A NOTIFICATION WAS THEN MADE TO THE NATIONAL RESPONSE CENTER WHILE NATURAL GAS WAS STILL BEING BEING RELEASED AND REPAIRS WERE ON-GOING. THE BODY OF THE 2-INCH VALVE AT THE FLANGE WAS FOUND CRACKED ON JANUARY 14, 2010, FROM SOIL STRESS. REPAIR CREWS ESTIMATED THE DEPTH OF FROST IN THE PREVIOUSLY EXCAVATED AREA TO BE 30-INCHES AND THE FROST DEPTH OUTSIDE OF THIS AREA TO BE 12 TO 18 INCHES. APPARENTLY THE FROZEN SOIL EXPANSION CAUSED THE FAILURE AS THE BREAK ORIGINATED FROM PRESSURE PUSHING DOWNWARD ON THE MAIN.