Challenge

As mining operations in the City of Irwindale expanded deeper and, in many cases, below the groundwater table, the City faced complex geotechnical and regulatory challenges. Multiple open-pit aggregate mines required comprehensive evaluation of slope stability, seismic risk, groundwater impacts, and compliance with California’s Surface Mining and Reclamation Act (SMARA). The City needed a trusted technical partner to help address concerns raised by regulatory agencies while ensuring the long-term safety and viability of its mining operations.

Solution

For more than 20 years, GLA has served as the City’s geotechnical advisor, providing advanced engineering analyses and ongoing technical support for ten major open-pit mining sites. Our team conducted extensive geologic mapping, Becker-hammer drilling, laboratory testing, groundwater evaluations, seismic hazard assessments, and static and dynamic slope stability analyses to characterize subsurface conditions and assess long-term performance.

Beyond site investigations, GLA helped shape industry best practices by playing a leadership role on the Irwindale Technical Advisory Committee and other technical committees that developed guidance for mine slope stability, drainage and erosion control, and underwater and above-water backfilling. We continue to support the City through geotechnical consulting, construction oversight, SMARA inspections, regulatory compliance assistance, and operational reviews.

Results

GLA’s technical expertise helped the City establish a defensible engineering framework for managing complex open-pit mining operations while addressing critical safety and regulatory requirements. The guidelines developed through these collaborative efforts have since been widely adopted by mine operators and regulatory agencies throughout California. Today, the City continues to rely on GLA’s engineering insight to support mine operations, reclamation activities, and long-term regulatory compliance across its mining portfolio.

“Successful mine management requires more than solving today’s challenges—it requires building the technical foundation for decades of safe and sustainable operations. By combining rigorous geotechnical analysis with practical regulatory guidance, we helped the City of Irwindale make informed decisions that continue to benefit the community and mining industry today.”

 — Luis Mariscal,  PE - Project Manager