The Trans-Alaska Pipeline System Synthetically Insulated Workpad—An Evaluation of Present Conditions

The purpose of the insulated workpad study, described in the following paper, was twofold. First, the owners of the Trans-Alaska Pipeline System (TAPS) needed an evaluation of present conditions of the insulated pad to determine the feasibility of plans by builders of the Alaska Natural Gas Transportation System (ANGTS) to reuse the TAPS workpad for parallel construction. Secondly, since the integrity of the elevated support system used by TAPS in insulated workpad areas was dependent on the insulation maintaining a shallow active layer, it was important for Alyeska (the operator of TAPS) to be assured that the insulated pad was performing as designed. The fieldwork undertaken for the study included test pitting and probing to determine the depth of thaw, sampling the insulation, and installing thermistors for long-term temperature monitoring. The insulation samples were tested for several parameters. Total performance of the workpad was better than expected, although several types of problems were encountered. Most were related to construction practices or postconstruction activity.