The Perchlorate Site: A case study that put Environmental Sequence Stratigraphy (ESS) on the map

In 2009, Environmental Sequence Stratigraphy (ESS) technology was applied to develop a conceptual site model (CSM) for a complex contaminated site near Saugus, California. This resulted in a significant reduction in projected cleanup costs and was one of the first examples of how applying robust geologic analysis to existing subsurface data can optimize site remediation. The Perchlorate Site was historically used for explosives and rocket manufacturing. The site spans nearly 1,000 acres and features rugged terrain, complex fluvial geology, and active faulting as it is adjacent to the Santa Clara River, and the San Gabriel Fault Zone extends through the site.

Groundwater supplies 25–45% of the local municipal water. Groundwater contamination, primarily perchlorate and chlorinated volatile organic compounds (VOCs), was found in multiple zones within the Alluvium and Saugus/Pacoima Formations. The site required a groundwater pump-and-treat system to contain a mile-long perchlorate plume that was impacting groundwater production wells. Traditional lithostratigraphic models failed to represent the site’s complex subsurface heterogeneity, leading to an oversimplified CSM to guide the remediation design.

By applying ESS methodology to integrate existing site data (geophysical logs, borehole logs, groundwater chemistry, and aquifer testing) within a sequence stratigraphic framework, the team defined hydrostratigraphic units (HSUs) representative of the complex subsurface and identified key contaminant migration pathways. This refined CSM enabled a more targeted extraction well network, significantly reducing the treated water volume and focusing on impacted strata only. This optimized remediation design based on a better understanding of the subsurface, resulted in a dramatic cost reduction—from $82 million to $26.5 million in estimated groundwater extraction and treatment cost over 30 years, and over 70% reduction in extracted groundwater volume while gaining regulatory approval for the revised containment system. The study highlights the value of oil industry stratigraphic techniques in environmental remediation and groundwater management.