In the foothills just west of Cupertino, the Lehigh Permanente Quarry forms a 3500-acre scar in the otherwise green and undeveloped hillsides of the Santa Cruz Mountains. For decades, mining operations there have discharged toxic selenium into Permanente Creek and contributed to air pollution, noise, and dust in the region. Up until now, Lehigh’s mining operations were expected to cease in 2025.

Now, however, Lehigh has applied to Santa Clara County for an expansion of mining operations that will last until 2050, destroy the ridgeline bordering Rancho San Antonio Open Space Preserve, and add about 200,000 truck trips every year hauling rocks and dirt through the streets of Cupertino.

Lehigh’s Current Opperations

The Permanente Quarry dates back to before World War II, when it was the Kaiser Permanente Cement Plant. (It’s now owned by Lehigh Heidelberg Cement, a German company that is one of the world’s largest cement producers.) Over the decades, constant mining of limestone and rock for cement and aggregate has created a massive quarry pit covering hundreds of acres and plunging almost 1,000 feet deep.

To protect against dangerous over-mining of the north slope of the quarry pit, a scenic ridgeline easement – a property right owned by Santa Clara County that prohibits damage to the ridgeline – was established in 1972. This easement not only guards against excessive mining that could cause landslides, it protects the view of the hillsides for the residents of Santa Clara County. The ridgeline, which forms the visual border between the quarry pit and Rancho San Antonio Open Space Preserve, is about ¼ mile from hikers on Rancho San Antonio’s Stephen E. Abbors Trail.

For years, local residents have suffered through the noise, dust, and air pollution from a massive heavy industrial operation just hundreds of yards from their homes, waiting on the expected end of Lehigh’s mining activity in 2025. Because Lehigh couldn’t dig further into the hillside without violating the scenic easement, they would have to stop their operations. Further, the 2012 Reclamation Plan, which details exactly how Lehigh will clean up the site after the mine is closed, estimated that mining operations would cease in 2025.

Lehigh Makes a New Proposal

Despite these deadlines, in 2019, Lehigh submitted a proposal asking the County to allow them to dig further into the hillside and cut into the ridgeline, in violation of the scenic easement. Lehigh claims that this must be done in order to stabilize the slope, which otherwise will continue to erode. If granted, this expansion would not only violate the scenic easement, it would extend the life of the quarry far beyond what was contemplated in the Reclamation Plan approved by the County.

However, if the slope is in a dangerously unstable and erodible condition, this must be due to Lehigh’s own mining activities – which suggests doubt as to Lehigh’s ability to safely conduct mining operations. The fact that under this new plan, Lehigh estimates that mining operations would continue until 2050 suggests that Lehigh’s primary motivation is not improved safety, but the desire to excavate more material from the slope than is currently allowed by the 2012 Reclamation Plan or the scenic easement.

In addition, Lehigh has proposed to import 20 million cubic yards of dirt to fill its quarry pit when the mine is closed. The 2012 Reclamation Plan required using material already onsite for this Stop the Lehigh Expansion purpose. According to Lehigh’s own documents, importing such a massive amount of dirt would require about 200,000 truck trips annually, or more than 800 truck trips per weekday (assuming no trucks run on weekends). The noise and air pollution resulting from over 800 dirt-filled semitrailer trucks driving to and from the quarry every weekday for 20 to 30 years would be substantial.

Lehigh’s Mining Operations Have Other Unacceptable Environmental Impacts

The harmful impacts of Lehigh’s mining operations go beyond the destruction of the hillside and ridgeline and the additional trucks. Lehigh’s cement plant is one of the worst polluters in the state for hydrochloric acid, sulfur oxides (SOx), nitrogen oxides (NOx), and volatile organic compounds (VOCs), among other pollutants. Lehigh’s mining operations result in toxic discharges of selenium into Permanente Creek. As a result of a Sierra Club lawsuit, Lehigh must remediate its selenium discharges, but the Regional Water Quality Control District’s monitoring shows that periodic violations still occur. All these impacts would be continued for decades longer if Lehigh’s quarry expansion were approved.

The County Should Deny Lehigh’s Proposal

Santa Clara County has the authority to deny Lehigh’s request to amend the 2012 Reclamation Plan. Although Lehigh has “vested rights” to continue any historic mining activities established before the County started requiring industrial operations to apply for use permits or otherwise restricted their activities, Lehigh has no right either to expand outside of the historic mining area or to undertake any new and different type of activities. Further, vested rights or no, the County has absolute authority to enforce the scenic easement that protects the ridgeline for the benefit of the public. And last, the County need not consider Lehigh’s request to amend the 2012 Reclamation Plan to allow Lehigh to haul 20 million cubic yards of dirt to the quarry.

Green Foothills will be working to prevent the County’s approval of these harmful impacts. The scoping process for the draft Environmental Impact Report (EIR) is expected to be initiated sometime this year. We will keep you informed of how and when you can provide comments on the environmental review process.