After 84 years, the cement kiln at Lehigh Quarry – the largest single source of air pollution in Santa Clara County – will now be shut down for good and demolished as a result of a legally binding agreement entered into with Santa Clara County. Lehigh has also withdrawn its earlier request to expand its mining activity, although the company still intends to continue processing its stockpiles of already-quarried rock. This marks a major step towards the ultimate goal of ending Lehigh’s operations entirely and restoring the quarry site to open space.

Long History of Environmental Violations and Pollution

Located in the foothills southwest of Cupertino, just south of Rancho San Antonio Open Space Preserve, the Lehigh Quarry is a scar in the landscape that’s more than a mile long and hundreds of feet deep. Since its origin in 1939, the quarry has destroyed wildlife habitat both by excavating the hillsides of the Santa Cruz Mountains and by dumping immense piles of quarried material near the quarry pit. The quarry has also discharged selenium – a toxin that can cause birth defects in wildlife – into Permanente Creek, which flows through the quarry site. The Sierra Club Loma Prieta Chapter sued Lehigh in 2011 to stop the selenium discharges.

The Lehigh cement plant, located at the quarry site, has for decades been the largest single source of air pollution in Santa Clara County. Pollutants included toxic chemicals like mercury as well as greenhouse gases and significant amounts of dust and particulates, all of which created health concerns for the public.

Together, the quarry and cement plant have racked up over 2,100 violations of local, state and federal laws just within the past 10 years. Because of this egregious track record, Santa Clara County was preparing to hold a hearing to potentially revoke the cement plant’s use permit as a public nuisance.

Legally Binding Agreement to Demolish Cement Kiln

In late 2022, Lehigh stated that it was voluntarily closing the cement kiln, which had not been operational since the start of the COVID pandemic. On August 15, Lehigh and Santa Clara County entered into a legally binding agreement that Lehigh will never attempt to re-start cement manufacture and will begin the process of demolishing the cement kiln. However, Lehigh may still use the cement plant site for storage and distribution of cement.

Lehigh’s plans for the quarry have also been revised. Earlier this year, Lehigh withdrew their proposed Reclamation Plan Amendment (RPA) from 2019 which would have allowed them to expand their mining activities by removing the top of the ridgeline separating the quarry pit from Rancho San Antonio. Instead, Lehigh’s new proposed RPA states that they will only process their giant stockpiles of already-quarried material.

Concerns Remain About Future Quarry Activity

Even with the closure of the cement kiln and the cessation of new mining in the quarry pit, Lehigh’s industrial operations – including storage and distribution of cement and processing of already-quarried material – may continue for many years. Green Foothills will be monitoring Lehigh’s activities for potential environmental concerns and to ensure that the entire quarry site is ultimately reclaimed and restored to open space.