NORTHERN NATURAL GAS CO — Integrity Assurance Notification

MAOP RECONFIRMATION METHOD 6Northern 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).#