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Location: Sunol Valley, Alameda County

Client: The DeSilva Group

Scope: Environmental Analysis - Permit Revision and Extension


The DeSilva Group operates the Sunol Valley Aggregate Quarry which is an open pit sand and gravel quarry on a 381-acre site at 6527 Calaveras Road, approximately one mile south of I-680 in the Sunol Valley portion of unincorporated southern Alameda County. DeSilva Group needed a quarry permit amendment from the County that would allow an increase in the production potential of the quarry by expanding the area under permit by approximately 58 acres and deepening the depth of excavation to a maximum 400 feet. DeSilva also wanted to extend the life of the permit by 30 years and to add additional ancillary uses at the site, including an asphalt batch plant and a concrete plant.


The proposed amendments to the quarry permit constitute a “project” under CEQA. DeSilva Group selected Lamphier-Gregory as the environmental consultant to prepare an EIR for the proposed surface mining permit amendment. The EIR was prepared for and under the direction of the County of Alameda

Significant Environmental Concerns

  • Water: ground water seeps or flows into the bottom of the pit and needs to be removed. The water is pumped out of the active mining pit and pumped to a wash water pond, a fully spent 140-foot deep prior pit quarry. Water from the holding pond is used in the initial washing of newly excavated material. The used wash water is then pumped back out of the plant to a silt pond where sediment settles to the bottom and water percolates by gravity back into ground water.
  • San Antonio Creek: potential impacts to the water quality and the riparian
  • The community of Sunol
  • The San Francisco Public Utility Commission
  • Air emissions, diesel and other particulate emissions


 All potentially significant impacts were reduced to less than significant levels through avoidance and/or mitigation measures. The EIR was certified and the proposed quarry permit amendments were approved on unanimous vote of the County Planning Commission. No appeals were filed and the Project is being implemented. 


Site plan courtsey of Benchmark Resources