From then to now: an overview of operations

Today, the Permanente Quarry primarily produces limestone suitable for use in cement and aggregate production and greenstone, a key component of roadbed and other construction applications. They’re both the products of a geological gift from Mother Nature: the unique concentration of limestone found in the hills near Cupertino, Los Altos Hills and Palo Alto.

The quarry, quantified

As a result, this property is able to produce roughly 50% of the cement used in the Bay Area and about 70% of the cement used in the communities of Santa Clara County; the cradle of Silicon Valley.

Present day operations

Current surface mining primarily focuses on extraction of limestone and other minerals from a single location called the North Quarry. From there, the materials are either transported to the Rock Plant, located on the southeast portion of the quarry, or conveyed to the company’s Permanente Cement Plant, which lies adjacent to the quarry on the east. While the Permanente Cement Plant is owned by the same company, it is separately permitted, is subject to different regulatory standards and is not considered part of the quarry.

More Fast Facts

  • Hanson Permanente Cement, Inc. owns the quarry and Lehigh Southwest Cement Company is the operator.

  • Hanson Cement acquired Kaiser Cement in 1986. The company was renamed Hanson Permanente Cement in 1999.

  • The quarry occupies a portion of a 3,510-acre property. Most of this land is subject to the County’s land use jurisdiction. Non-mining portions of the land are in the cities of Cupertino and Palo Alto.

  • The site employs geologists, hundreds of operators, technicians, chemists and engineers.

  • The cement plant is why one railroad line runs through Cupertino.

  • Permanente Quarry has vested mining rights, meaning the quarry was established legally under the regulations in place at that time and is allowed to continue until the use ceases. These mines are “grandfathered” against subsequent zoning changes and do not require use permits for certain types of expansion.