Seepage Investigation at a Tailings Storage Facility in San Luis Potosí, Mexico—Case Study No. 1 of Rationalizing the Unusual and Unexpected

In this paper, the author presents the results of a forensic investigation at a tailings storage facility (TSF) located in San Luis Potosí, Mexico. The purpose of the study is to investigate potential seepage observed along a localized portion of the existing embankment dam. Field observations and predictive modeling of seepage and slope stability have been revisited and applied to obtain a better understanding of dam performance and to estimate the probability of failure of embankment slopes considering the existing dam configuration and a proposed dam raise. The investigation comprises visual observations, test pitting, field and laboratory tests, seepage analyses, slope stability analyses, and a review of the quality control construction data. The results suggest that the observed localized ‘damp’ portion of the embankment is non-hydrostatic. Therefore, a raise of the existing dam above the current dam configuration would be feasible provided best dam engineering practices are followed. Design considerations should focus on the location of the tailings pond. Instrumentation plans should consider monitoring of piezometric heads within the existing and new embankments, and future placement of fill materials should be in accordance with appropriate earthwork specifications.