{"operation":"document","citation":"PHMSA 26-371659","title":"NORTHERN NATURAL GAS CO — Integrity Assurance Notification","source_type":"inspection","agency":"Pipeline and Hazardous Materials Safety Administration","status":"historical","official":true,"published_on":"2026-04-30","effective_on":"2026-04-30","summary":"GAS TRANSMISSION in WI; MAOP RECONFIRMATION METHOD 6; PHMSA status: RESOLVED.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-leading-ian-26-371659-operator-13750.json","markdown":"https://regulus.evalyn.ai/document/phmsa-leading-ian-26-371659-operator-13750.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-leading-ian-26-371659-operator-13750","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/data_statistics/pipeline/SRCR_and_Integrity_Assurance_Notifications.zip","body":"Northern Natural Gas (NNG) is working to reconfirm the maximum allowable operating pressure (MAOP) of its WIB11901 Tomah 10-inch branch line segment in the state of Wisconsin in accordance with 49 CFR 192.624(a). This segment is a single source for NNG's Tomah and Viola systems and an outage to perform a pressure test or pipe replacement would make it difficult to maintain customer service. The segment is also located in a swamp and wetland area, which would make typical trenched construction difficult to permit and perform. NNG plans to use an alternative technology per 49 CFR 192.624(c)(6), Method 6: Alternative Technology, to reconfirm an MAOP of 719 psig for select pipe pups on this segment. NNG plans to reinforGary.Krichau@nngco.comce the pups with composite wrap to a design pressure greater than 1.5 x MAOP and to a stress level at MAOP of less than 30% SMYS. The purpose of this report is to document Acuren's alternative technical evaluation and engineering analysis to support NNG's notification to the Pipeline and Hazardous Materials Safety Administration (PHMSA).","truncated":false,"body_characters":1086}