NOVA Chemicals
July 3, 2015
Executive Summary
Pipeline abandonment refers to permanently taking a pipeline out of service. Depending on a number of factors, sections of pipeline may be abandoned in place as short or long segments. Pipe materials abandoned in place will degrade over time. This study by NOVA Chemicals was commissioned by the PTAC Pipeline Abandonment Research Steering Committee (PARSC) to better understand the risks posed by pipe coating degradation products. Background information about PARSC is provided below.
This is a review of pipeline coating materials and their fate when pipelines are left in place at the end of their useful lifetime. The makeup and effects of materials capable of being leached out of the coating materials were assessed. Published information suggests that easily leachable chemical compounds in coatings have been in the process of being leached from coatings from the moment they were first put into the ground. Therefore, the chemicals that are soluble in water and easily removed have probably already leached out of the coating materials during the lifetimes of the pipelines.
The coating chemicals that are less likely or able to be dissolved in water, will not be easily leached and for the most part will remain in the coating material. It is expected that over time some minimally slow leaching will probably occur. For example, coal tar and asphalt coatings contain what are called polyaromatic hydrocarbons or PAHs. These relatively large chemical compounds prefer to be associated with other hydrocarbon rather than water. Very low concentrations may dissolve in water in the soil where the pipeline is located but they will preferentially be absorbed by soil organic carbon (for example: decayed plant material or soil humus) and will this will prevent them from migrating through soil water or to groundwater where they may travel to other locations. Additionally, these molecules can be biodegraded slowly by soil bacteria and fungi over time. Because leaching and degradation of pipeline material components have been ongoing for many years, by the time a decision has been made to abandon a pipeline and leave it in place, no additional risks from the coating materials are anticipated.