SEMCO ENERGY GAS COMPANY

Incident Narrative

ON MARCH 13, 2022, AT 1:58, AM, SEMCO ENERGY GAS COMPANY RECEIVED A CALL FROM THE MICHIGAN STATE POLICE INDICATING 908 COLLEGE AVE., IN HOUGHTON, MI HAD EXPLODED. THE SEMCO TECHNICIAN ARRIVED ON SITE 21 MINUTES AFTER THE INITIAL CALL, (INDICATED TIME IS 3:19 AM DUE TO DAYLIGHT SAVINGS TIME CHANGING AT 2:00 AM ON MARCH 13TH). WHEN THE SEMCO TECHNICIAN ARRIVED, THE HOUGHTON FIRE DEPT. WAS ATTENDING TO A FIRE AT THE STRUCTURE. ONCE THE FIRE WAS UNDER CONTROL, THE TECHNICIAN WAS ABLE TO SECURE GAS AT THE GAS METER SET. THROUGH THE LEAK INVESTIGATION PROCESS, THE TECHNICIAN DETERMINED THERE WAS A PROBABLE UNDERGROUND LEAK BASED ON LEL READINGS FOUND AT THE REAR OF THE RESIDENCE. THE TECHNICIAN CONTINUED THE LEAK INVESTIGATION AND FOUND GAS READINGS AT SURROUNDING BUILDINGS AND EVACUATED BUILDINGS ON COLLEGE AVE. AND ON E LAKESHORE. GAS FLOW WAS THEN SHUTOFF IN THE AREA IN WHICH READINGS WERE FOUND AND GAS WAS PURGED IN THOSE AREAS TO REDUCE GAS TO SAFE LEVELS. AN INVESTIGATION INTO THE SOURCE OF THE GAS LEAK WAS CONDUCTED IN THE SPRING WHEN GROUND CONDITIONS PERMITTED. A CAMERA WAS USED TO EVALUATE THE INSIDE OF THE PIPE THAT WAS SHUT DOWN DUE TO THE LEAK. THAT PROCESS INDICATED A DEFORMATION, WHICH THEN LED TO AN EXCAVATION TO EVALUATE. THE 2 IN. STEEL GAS MAIN WAS FOUND TO BE DAMAGED AT THE CROSSING OF A SANITARY SEWER LINE. THE DAMAGE ON THE PIPE WAS CONSISTENT WITH THE DIMENSIONS OF AN EXCAVATOR BUCKET. A METALLURGICAL EXAMINATION OF THE PIPE REPORTED THE DAMAGE CONSISTED OF OVERALL BENDING DEFORMATION, FLATTENING OF THE PIPE, AND DAMAGE TO THE PROTECTIVE COATING ON THE EXTERIOR OF THE PIPE. THIS DAMAGE WEAKENED THE PIPE MAKING IT MORE SUSCEPTIBLE TO FRACTURE OR CRACKING FROM EXTERNAL FORCES SUCH AS FREEZE/THAW CYCLES. GAS LEAKED FROM A CRACK IN THE PIPE AND MIGRATED THROUGH THE FROZEN GROUND AND INTO THE HOUSE AT 908 COLLEGE AVE. THE METALLURGICAL EXAMINATION ALSO REPORTED THE FRACTURE IN THE GAS MAIN WAS BRITTLE AND DID NOT EXHIBIT WALL THINNING OR CORROSION TO SUGGEST THE CRACK OR A PARTIAL CRACK ORIGINATED YEARS PRIOR TO THE EXPLOSION. DURING THE INVESTIGATION AND EXCAVATION OF THE DAMAGED PIPE, THE INITIAL OBSERVATION BEFORE THE PIPE WAS EXPOSED INDICATED A HOLLOWING OF THE SOIL NEAR THE FOUND CRACK, AND NO EVIDENCE OF DRY DIRT OR HARDENING OF THE SOIL CONSISTENT WITH A LONGSTANDING GAS LEAK. PHOTOS OBTAINED THROUGH A FOIA REQUEST INDICATED THE NATURAL GAS MAIN WAS LOCATED AND MARKED BY SEMCO, A FACT CONSISTENT WITH SEMCO'S LOCATING RECORDS. BASED ON THE RECORDS AND PHOTOS OBTAINED, IT IS REASONABLE TO BELIEVE THE EXCAVATOR DUG WITHOUT HAND EXPOSING THE GAS MAIN, AND AFTER THE MICHIGAN ONE CALL TICKET HAD EXPIRED. PHOTOS SHOWING THE TIME STAMP INDICATE THE DAMAGE LIKELY OCCURRED BETWEEN AUGUST 27TH AND AUGUST 28TH, 2008. THE EXCAVATOR ALSO APPEARED TO HAVE DAMAGED CONDUIT FOR A TELECOMMUNICATIONS LINE. SEMCO ENERGY WAS NEVER NOTIFIED OF THE DAMAGE TO THE PIPE DURING THE SEWER CONSTRUCTION. BASED ON THE INFORMATION GATHERED DURING THE INVESTIGATION, METALLURGICAL EVALUATION, AND INFORMATION REQUESTS, SEMCO CONSIDERS THE INVESTIGATION TO BE COMPLETED.