Vulnerability assessment for the Mijitayo Creek water treatment facility; Pasto, Colombia

The recent activity (February 1989-current) of Galeras Volcano and its proximity to the city of Pasto (Colombia) highlights the need for volcanic risk evaluation. With the volcano's summit towering 1600 meters above the city and a mere nine kilometers from its central square, the consequence of a lahar could be disastrous (Calvache, 2000). A lahar vulnerability assessment has been conducted specifically for the water treatment facility that lies upon the banks of the Mijitayo Creek in Pasto. This assessment was based upon data from the geologic record, qualitative structural data that affect the response of the facility to lahar processes, and simple open-channel flow calculations. This analysis is not a geologic study intended to advance the research of lahar composition or mechanism. Studying the potential reaction of the water treatment facility to lateral forces, boulder impact, and inundation will allow planning to mitigate the damages caused specifically to this facility in the event of a lahar. At the conclusion of this study, basic suggestions were made to contain or control flow damage. This study, which combines geologic field work, facility data, and flow computation, is an important example of the interface between geology and society, and is a method that can be used by similar facilities that are vulnerable to volcanic activity.