GAS TRANSMISSION NORTHWEST LLC — Integrity Assurance Notification

ASSUMED TOUGHNESSOpIDs: 405, 993, 2616, 2620, 39542, 6660, 13769, 15014, 30838, 31145, 31891, 32487 The purpose of this letter is to provide notification in accordance with §192.18 of TC Energy’s intent to use Other Appropriate, Conservative toughness values for pipe formed with Double Submerged Arc Weld (DSAW) longitudinal seam welds (LSW) as allowed by 49 CFR, §192.712(e)(2)(i)(E) rather than the generic toughness values prescribed in §192.712(e)(2)(i)(C) and §192.712(e)(2)(i)(D). The proposed toughness values for DSAW will be incorporated into TC Energy procedures including the TEP-IN-EMAT-G Analysis of EMAT In-Line Inspection Technologies and implemented within the following TC Energy Pipeline Operating Systems.#