(47cl) Quantitative Analysis of Environmental and Societal Risk for Onshore FUEL Pipelines

Combustible materials transportation by pipeline has been established as a safe and efficient mean.    Due to the low accidental frequency of incidents associated, it is socially accepted as favorable. However, like any other industrial practice it can be dangerous and represents risks to the society, environment and infrastructure. Since production sites are often away from consumption centers, increased demand in Colombia and the world has led to increased transportation needs, forcing the growth of pipeline networks.

Carrying out a-priori risk analysis could provide engineering tools to support decision making, related to the compatibility of activities within a territory (Land-use Planning). This allows taking preventive measures with respect to potential accidents. Hence, implementing scenario building enables to explore and clarify chain of possible events, including actions and consequences. Also, it is important to define event probabilities; this is done using Event Tree Analysis (ETA). Subsequent phase consists of consequence analysis, where simulation is performed in order to determine effects intensity and then vulnerability values. Once all this is accomplished, risk assessment is completed.

So, this work aims to develop a methodology for the assessment of societal and environmental risk associated with: loss of containment in onshore fuel liquid pipelines and consequences of critical events, as radiation, overpressure and contamination effects. As risk values vary along pipelines due to differences in environmental and societal conditions, analysis is performed for segments of a pipeline, including analysis of causes and types of events.

For societal risk assessment the methodology includes some guidelines to develop a segmentation process. Risk changes along the pipeline due to differences in environmental and societal conditions in order to define manageable pipeline sections for analysis. It is also necessary to identify the probable events and their probabilities; in this case MIMAH methodology and historic analysis is used. Then consequence analysis is performed for each segment, determining the intensity of overpressure and radiation effects caused by the previously defined events. This determination is done by means of simulations performed on specialized software and then using probit equations the vulnerability is estimated. With vulnerability and probability values known, risk can be estimated. As a result, risk values for people are determined and expressed as individual risk contours and FN curves for societal risk.

In addition to the societal impacts, assessment of environmental contamination is also done. It is known that hydrocarbon releases are a real hazard to the environment as they produce contamination to soil and groundwater. In Colombian topography, mountains and slopes are mostly present. This generates scenarios out of the right of way making analysis of onshore hydrocarbon spillages even more relevant in this territory. Therefore, environmental effects on soil are determined considering mass balance of infiltrated and evaporated material in horizontal and inclined surfaces. Consequently, effective volume remaining on soil surface is determined to establish amount of material available for migration pathways. Environmental damage is then estimated taking into account depth of infiltrated material, associated to soil excavation and off-site disposal, soil clean-up and groundwater clean-up costs. As a result, environmental risk values are presented as risk indexes in terms of remediation action costs, defining an environmental local monetary damage. Contamination is analyzed in order to determine average soil volumes which need to be treated, considering intervention, mitigation and remediation times.

This methodology is targeting to support decision-making in Colombia in early stages of analysis, with respect to land-use planning, from a societal and environmental point of view. A total risk index is calculated, in order to be used as a comparative tool for ranking different projects or pipeline sections. This total risk index is calculated turning both societal and environmental risk in equivalent terms, meaning monetary terms. It is represented as an FM curve (frequency vs. millions of dollars, euros, etc.). Simultaneous assessment of both human and environmental risk is remarkable, as it integrates and supports decision making.

This methodology is applied on a case study to illustrate how it can support decision making (related to Land-use planning and to alternatives choice).Taking into account international societal risk criteria, it will be determined whether these values can be accepted or should be reduced. Therefore, coupling risk assessment of environmental contamination and damage to exposed population allows quantifying risk and thus, supporting decision making within the territory.