Quarry retirement and land restoration for a new future
The Permanente Quarry is a historical mining operation located in Santa Clara County, known for limestone and construction aggregate extraction. Lehigh Southwest Cement Company has submitted a proposed 2023 Reclamation Plan Amendment (RPA) to replace the 2012 Reclamation Plan. This newly proposed RPA focuses on the final closure and reclamation of the site, as there will be no further limestone excavation or clinker production. The goal is to restore the area in accordance with California Surface Mining and Reclamation Act “SMARA” requirements for future use according to relevant land use regulations.
Grading steep areas for stability
Backfilling the Quarry with on-site and imported fill
Covering the West Materials Storage Area (WMSA), East Materials Storage Area (EMSA), and Quarry with suitable closure material (generated on-site and imported)
Buttressing Quarry walls with imported fill
Removing aggregate stockpiles
Revegetating, to control wind and water erosion and assist in reclaiming viewsheds.
Reduces the reclamation plan boundary by 30 percent, from 1,274 acres to 921 acres (removes areas of known limestone reserves south of Permanente Creek from this RPA by withdrawing a 353-acre mostly undisturbed area;
Incorporates new SMARA requirements enacted since the 2012 Reclamation Plan Amendment;
Incorporates new geotechnical stability information;
Retains the Quarry north wall ridgeline;
Ensures interim and long-term water quality and advances closure plans pursuant to issued Waste Discharge Requirements (“WDRs”);
Includes the expected amount of cover materials needed for the WMSA, EMSA, Quarry cover, and Quarry buttress fill;
Provides a location to reuse clean imported soil materials from off-site regional projects, thereby reducing regional vehicle miles traveled and associated air and GHG emissions;
Continues processing and selling previously mined aggregate resources; and
Completes reclamation in phases, consisting of regrading, backfilling the Quarry, and importing cover and fill.
Areas Affected by the proposed Reclamation Plan Amendment
The Permanente site has been in operation since 1903. The proposed RPA calls for reclamation to be performed in a series of phases, with final reclamation activities concluding by December 31, 2065. No new surface disturbances or habitat will be affected by the proposed RPA.
The following are the reclamation areas subject to the RPA:
The topography of the Permanente property is generally steep. Under the proposed RPA, the Quarry highwalls will be covered by fill at lower elevations and reclaimed in a stabilized benched configuration at upper elevations. Additionally, the upper bench will meet current seismic standards, and the buttress area below the crest of the north highwall will remediate unstable conditions of the upper Quarry walls. The buttress design will maintain the height of the existing ridge crest along the north Quarry highwall. A portion of the on-site suitable backfill materials will be generated via regrading the greenstone slide of the west wall of the Quarry, upper Quarry slope stabilization, grading at the shop and office area, and excavation of the lower WMSA. The remaining soil will be imported clean fill from, e.g., regional infrastructure and construction projects, and other sources. Vehicle and truck traffic required to accomplish fill import will be similar to historic baseline levels at the facility.
The WMSA is an approximately 173-acre area with about 48 million tons of low-grade limestone and greenstone. Under the proposed RPA, most of the WMSA will remain in place to ensure long-term surface and groundwater quality. Importantly, the reduction of WMSA materials used as Quarry backfill will also serve to reduce risks to water quality. The WMSA will be graded to 2.25:1 or flatter, and capped with cover material and soil for revegetation.
The EMSA is an approximately 75-acre area with a design capacity of 6.5 million tons of waste rock. The EMSA will be graded to 2.25:1 or flatter and capped with cover material and soil for revegetation. Closure of the EMSA pursuant to the proposed 2023 RPA and the sites’ WDRs will ensure that the materials are adequately protected and isolated.
The Shop and Office, consisting of primary and secondary crushing stations, offices, and maintenance areas, will continue to support aggregate processing operations and equipment for the proposed reclamation and closure process. Limited grading is scheduled for this area with final slopes between 2:1 and 3:1. Ultimately, buildings and equipment will be removed.
The approximately 19-acre Rock Plant will remain an active rock processing facility for construction aggregates, consisting of crushing, conveying, screening, and processing facilities that produce various types of aggregate products, which will be stored in stockpiles until transported to customers. Ultimately, equipment will be removed and the area graded at 3:1 slopes.
The main haul road adjacent to the Cement Plant provides access for all vehicles and equipment from the site entrance to the reclamation areas, and will remain following reclamation for site access.
The Permanente Creek Reclamation Area is an approximately 49-acre historic mining location adjacent to the WMSA, which does not require reclamation under SMARA because the disturbance pre-dated SMARA’s effective date. Despite this, Lehigh has voluntarily agreed to reclaim that area.
Best management practices will be implemented on-site until vegetation is established that meets SMARA's current erosion control standards. Additionally, native vegetation species consistent with surrounding undeveloped areas of the property will be used, along with interim erosion-control planting, hydroseeding of the finished slopes, and tree and shrub planting on contoured benches and riparian drainages. The revegetation density will consist of 200 to 400 plants per acre and from 20% to 60% cover, depending on the reclamation surface.
Upon completion of the proposed reclamation, most surface runoff from the site will return to Permanente Creek. SMARA water quality goals and performance standards will be achieved through compliance with applicable water quality standards via Permanente's existing WDRs. These include the approved final closure plan and site-specific acceptance criteria applicable to materials imported for backfill or cover purposes.