In August, Santa Clara County entered into a binding agreement with Heidelberg Materials and Lehigh Southwest Cement Company, the owners of the Lehigh Cement Plant to permanently cease operations at the cement plant adjacent to the quarry.
The quarry, which shares a border with Rancho San Antonio Open Space Preserve, has been mined and supplied cement to the region for more than 80 years. The company announced that they halted all kiln operations in 2020. The binding agreement make the suspension of cement production permanent. Heidelberg intends to continue to sell aggregate previously mined and stored on site.
The ending of operations of the cement plant and lessening of quarry activities has led to a significant decrease in airborne dust into Rancho San Antonio County Park & Open Space Preserve.
Midpen has been working closely with the county and in 2021 entered into an agreement to share enforcement rights and monitors Heidelberg’s compliance with the ridgeline easement held by the county, which protects the ridgeline from mining and protects Midpen’s Rancho San Antonio Preserve. This allowed Midpen to take an active role in safeguarding the environmental and visual qualities of the ridgeline as a strategic approach to protecting the natural resources of the land and the health and well-being of the surrounding communities.
While the closure of the cement plan is a promising step forward, eyes now turn toward the future of the quarry and cement plant site. In June 2023, Heidelberg submitted a reclamation plan amendment application for the quarry to the county, which details their proposal to continue the sale of aggregate materials, cessation of new mining and future reclamation of the quarry. Reclamation plans are required by state law and compliance with state mining laws is administered by the county. Reclamation plans can be amended at the operator’s discretion, subject to compliance with state mining laws and new mining could be proposed in a future reclamation plan amendment.
Midpen has reviewed the reclamation plan amendment and has raised concerns about plans to keep massive waste rock piles in place and to fill the quarry pit by trucking imported fill. This proposed plan will take significantly longer, leaving the quarry walls below the ridgeline unsupported for 30-40 years, increasing the risk of catastrophic failure over that time period.
The future of the site is a critical issue for surrounding communities, both human and wildlife alike. The county and Cupertino entered into a mutually agreed upon policy framework for how to consider future uses on the site. Midpen will work with our county and city partners to continue advocating for the restoration of Permanente Creek, preservation of surrounding undeveloped open space lands on Heidelberg property, improvements to the reclamation plan to support long term slope stability, sufficient restoration to improve habitat connectivity through the reclaimed quarry landscape, appropriate use of the cement plant site and a trail connection from Stevens Creek Boulevard to Rancho San Antonio Preserve.