CEMEX Clayton Quarry

Project Overview

Project Location

The project site is located at 515 Mitchell Canyon Road, on the east side of Mount Zion, approximately one-half mile south of the city of Clayton in an unincorporated portion of the County. Surface mining disturbances are planned on approximately 190 acres within a 335-acre property.

Project Description

The applicant, CEMEX, is requesting approval of a revised Reclamation Plan which includes the following components: 

Clayton Quarry view of hillside surface mining
  • Reclamation over an anticipated period of 47 years to a post-mining land use of open space;
  • Reduction of the surface mining disturbance footprint relative to the existing reclamation plan that leaves the east rim of the quarry intact, providing visual buffer between the quarry and view sheds to the east;
  • Permanent overburden fill areas;
  • Final grading contours reflecting a maximum depth of excavation at elevation 110 feet above mean sea level (msl) with finish slope angles that achieve adequate factors of safety;
  • A final drainage plan that provides for the quarry pit to slowly fill with stormwater following reclamation to form a quarry lake with a controlled outflow that conveys stormwater to natural drainage courses and man-made drainage facilities;
  • Removal of facilities, structures and equipment associated with mining;
  • Revegetation of the quarry east rim, overburden fill areas, and processing plant site to a combination of chaparral and grassland habitats that feature California native seed mixes;
  • Elimination of requirements to backfill, grade, and compact the quarry floor and benches, given that the planned open space end use would provide for a future quarry lake;
  • Clarification of pre-Surface Mining and Reclamation Act (SMARA) (1976) disturbance areas, including any areas disturbed outside the boundaries of the approved reclamation plan;
  • Removal of 79 out of 123 existing trees, to be replaced with 400 foothill pine trees that would form a tree screen along the quarry east rim;
  • Compliance with current State reclamation standards to be achieved during reclamation; and
  • An exception request to Division 914 of the Contra Costa Code of Ordinances (Offsite Collect and Convey requirement).

In addition, and in response to stakeholder input, CEMX has incorporated into the project a new screening berm (between the existing processing plant site and residential communities to the north).

County File #’s CDLP15-02030 and 31


  1. Project Milestones
  2. Documents and DEIR
  3. Contact Us

Current Project Status

The Draft Environmental Impact Report (DEIR) is available for public comment was published on February 18, 2021. 
The comment period for the DEIR extends from February 18, 2022, to April 4, 2022. 
View Notice of Availability (PDF)

Project Milestones

March 16, 2020

The Zoning Administrator took comments on the Notice of Preparation.

February 14, 2020

The Notice of Preparation (NOP) was posted on February 14, 2020. 
View Notice of Preparation (PDF)