Problems beneath the Tracks: Condition Assessment of 1940s Vintage Cast Iron Water Mains underneath the Alaska Railroad: Fid-Bau Portal

Problems beneath the Tracks: Condition Assessment of 1940s Vintage Cast Iron Water Mains underneath the Alaska Railroad

Nuss, Stephen / Garrett, Chris

The Anchorage Water and Wastewater Utility (AWWU) owns and operates 1940s vintage cast iron water mains that are within the Alaska Railroad yard complex. These 10-, 12-, and 16-in. mains are some of the oldest mains within AWWU's distribution system. Previous failures on the 10-in. main raised concern about the integrity of the 12- and 16-in. mains. AWWU retained Pipeline Inspection and Condition Analysis Corporation (PICA) to perform condition assessment of the mains to determine appropriate rehabilitation or replacement timing. The use of PICA's technology required the mains to be taken out of service. Due to the location of the mains adjacent to and directly under active railroad tracks, temporary water system construction would have been extremely costly to construct. Because temporary water could not be provided, work was performed in segments during limited six- to eight-hour windows to work around railroad maintenance and tourism company schedules. The physical location and limited time constraints provided challenges to AWWU and PICA's performance of the work. Through early planning, stakeholder coordination, and the ability to adapt to changes, the inspections were performed over a one-week period in late August and early September 2013 and produced data that validated the need to not only replace the 10-in. line, but also replace or rehabilitate portions of the 12- and 16-in. mains.