ALLIANT ENERGY - INTERSTATE POWER AND LIGHT COMPANY — Gas transmission and gathering — incident on 2013-03-12

Gas transmission and gathering incident in CLINTON, CLINTON County, IA. Reported cause: EXCAVATION DAMAGE. Reported consequences: 0 fatalities, 0 injuries, 6000 NATURAL GAS released, $125,851 reported property damage. Operator-reported incident data submitted to PHMSA, generally within 30 days. Records may be supplemented or corrected and do not represent final agency causal findings.

Report number: 20130034.

Operator ID: 8170.

Reported incident date: 3/12/2013 9:15.

Cause detail: PREVIOUS DAMAGE DUE TO EXCAVATION ACTIVITY

Cause detail: EXCAVATION ISSUE

Cause detail: EXCAVATOR FAILED TO MAINTAIN CLEARANCE AFTER VERIFYING MARKS

Cause detail: A GAS LEAK WAS DISCOVERED BY AN INTERSTATE POWER & LIGHT (IPL) GAS SERVICE EMPLOYEE ON A 4 INCH STEEL LINE OPERATING AT 250 PSIG AT APPROXIMATELY 9:15 A.M. ON TUESDAY, MARCH 12, 2013 WHEN HE SMELLED A GAS ODOR AND HEARD GAS LEAKING. THIS EMPLOYEE IS A QUALIFIED FIRST RESPONDER AND IMMEDIATELY REQUESTED POLICE, FIRE, AND A GAS CONSTRUCTION CREW BE DISPATCHED TO THE SITE. (DATA FROM A PRESSURE RECORDER ON THE LINE INDICATES THAT THE LINE BREAK OCCURRED AT APPROXIMATELY 8:30 A.M. ON SUNDAY, MARCH 10, 2013.) WHEN AN IPL GAS CREW RESPONDED TO THE LEAK, THEY WERE INFORMED BY THE NEIGHBORING CHEMICAL PLANT PERSONNEL THAT THE PIPELINE HAS BEEN ENCROACHED UPON BY CONTAMINATED SOIL AND GROUNDWATER AND WAS NOW IN AN EPA SUPERFUND SITE. ONLY QUALIFIED HAZWOPER PERSONNEL ARE ALLOWED TO WORK ON THE SITE, REQUIRING IPL TO LOCATE AND MOBILIZE AN OUTSIDE GAS CONTRACTOR WITH THESE SPECIALIZED QUALIFICATIONS TO PERFORM THE REPAIRS. THE LINE IS A RADIAL FEED TO A SMALL TOWN WITH 190 CUSTOMERS AND THE LEAK WAS LOCATED ON A RURAL ROAD IN A RELATIVELY REMOTE LOCATION THAT DID NOT PRESENT AN IMMEDIATE RISK TO THE PUBLIC. IN ORDER TO AVOID AN INTERRUPTION OF SERVICE TO THE ENTIRE TOWN DURING COLD WEATHER, A TEMPORARY, ABOVEGROUND BYPASS LINE WAS INSTALLED. AFTER THE BYPASS STOPPERS WERE WELDED ON IN AN AREA OUTSIDE OF THE CONTAMINATED SOIL, A 2,600 FOOT LONG 2 INCH DIAMETER 100 PSIG HDPE ABOVEGROUND BYPASS LINE WAS CONSTRUCTED AND PLACED INTO SERVICE AT 11:54 P.M. ON WEDNESDAY, MARCH 13, 2013. AT THAT POINT, THE REPAIR CONTRACTOR MOVED IN AND MADE THE REPAIRS TO THE DAMAGED LINE BY CUTTING OUT AND REPLACING A 20 FOOT SECTION OF PIPE. THE LOST GAS CALCULATION FROM SUNDAY AT 8:30 A.M. UNTIL WEDNESDAY AT 11:54 P.M. YIELDED A VALUE OF APPROXIMATELY 6,000 MCF, WHICH EXCEEDED THE INCIDENT REPORTING THRESHOLD. THE LINE APPEARS TO HAVE FAILED FROM STRESS CRACKING AS A RESULT OF DENTS CAUSED BY PREVIOUS THIRD PARTY EXCAVATION DAMAGE. A STORM SEWER IMPROVEMENT PROJECT WAS COMPLETED IN THIS IMMEDIATE AREA DURING SUMMER 2011 AND THE DENTS APPEAR TO HAVE BEEN CAUSED BY THE TEETH OF A BACKHOE/TRACKHOE BUCKET. LEGAL ACTION TO RECOVER THE $245,000 ESTIMATED COST OF EMERGENCY RESPONSE, REPAIR, AND LOST GAS IS PENDING. THE CONTAMINANTS IN THE SOIL AND GROUNDWATER ARE VOLATILE ORGANIC COMPOUNDS (VOCS) AND POLYNUCLEAR AROMATIC HYDROCARBONS (PAHS), BUT DO NOT APPEAR TO HAVE HAD A HARMFUL EFFECT ON EITHER THE COAL TAR ENAMEL COATING OR THE PIPE. CATHODIC PROTECTION READINGS ON THE LINE HAVE HISTORICALLY BEEN VERY GOOD. DISCUSSIONS HAVE TAKEN PLACE REGARDING RE-ROUTING THE PIPELINE AWAY FROM ITS EXISTING LOCATION, BUT NO FIRM PLANS HAVE BEEN DEVELOPED AT THIS TIME. ADDITIONAL CLARIFICATION AS REQUESTED BY OPS CENTRAL REGION OFFICE. WHERE APPROPRIATE, CHANGES WERE MADE TO THE QUESTIONS REFERENCED: C6 - SELECTION IS LEFT AS RUPTURE, RATHER THAN PUNCTURE. INITIAL DAMAGE DID NOT PIERCE THROUGH THE PIPE WALL, BUT CAUSED A DENT THAT CREATED A STRESS CONCENTRATOR THAT EVENTUALLY CAUSED THE PIPE TO FAIL CIRCUMFERENTIALLY. E5A AND E5B - VALVES WERE NOT USED TO ISOLATE THE DAMAGE. HOWEVER, TWO MUELLER ANSI 600 TWO PIECE LINE STOPPERS WERE INSTALLED TO UTILIZE A BYPASS LINE TO AVOID A CUSTOMER OUTAGE. IN ORDER TO PROVIDE AN ANSWER FOR QUESTIONS E5A AND E5B, "MANUAL" VALVE WAS SELECTED. G14 AND G15 - IPL PERSONNEL WERE PRESENT WHEN THE LINE WAS INITIALLY EXPOSED IN 2011 FOR THE SEWER PROJECT, AND THE LOCATE MARKS WERE ACCURATE AT THAT TIME. G16 - DID THE DAMAGE CAUSE AN INTERRUPTION IN SERVICE? THIS QUESTION APPEARS ON THE PRINTED VERSION OF THE REPORT, BUT IS ABSENT ON THE ONLINE ENTRY FORM. THE CORRECT ANSWER IS "NO". G17 - CGA FIRST AND SECOND LEVEL DIRT ROOT CAUSES: RESPONSES WERE REVISED TO MORE ACCURATELY REFLECT THE ROOT CAUSE - EXCAVATION PRACTICES NOT SUFFICIENT AND FAILURE TO MAINTAIN CLEARANCE.

PHMSA trend classification: significant incident, not serious.

PHMSA standardized cause: EXCAVATION DAMAGE — PREVIOUS DAMAGE DUE TO EXCAVATION.

PHMSA indexed costs: $245,809 reported total cost, $134,007.425 in 1984 dollars, $306,530.436 in current-year dollars.

PHMSA trend flags, standardized causes, and indexed costs are analytical fields added to operator-reported incident data. They do not represent final agency causal findings.