Stevens Creek Quarry

The submitted application for a Reclamation Plan Amendment (RPA) will replace the approved Reclamation Plan for the Stevens Creek Quarry (the “Quarry”) that was approved by the Planning Commission in 1986 and most recently amended in 2009. The Application also proposes to reestablish and amend the expired Use Permit for Surface Mining to cover the entire property (referred to as Parcel A and Parcel B), and authorize the processing and sale of aggregate imported from Lehigh Permanente Quarry.

The Application contains the following components:

1. Use Permit for surface mining to apply to the entire site (Parcel A and Parcel B) for a term of 30 years and  import of up to 1 million tons of greenstone per year from Lehigh Permanente Quarry, immediately north of the subject site, for processing and sale, using a new haul road between the two Quarries. Other components of the Use Permit are summarized below:
   1. Surface Mining: SCQ proposes to expand mining operations along the western face of Parcel B highwall. Layback is needed for stability purposes and has been designed in a manner that also provides mineral reserves. The extended highwall will be developed by mining new benches to a bottom elevation of 860 feet mean sea level (msl) in the northern portion of the pit, and 700 feet msl in the center and southern portion of the pit. The site is estimated to contain approximately 41 million tons of reserves with approximately 30 percent waste. SCQ proposes to extract 2.6 million tons of Franciscan-aged greenstone rock for aggregate production annually with 30 percent of overburden waste factor, for a maximum annual crusher feed of 2 million tons per year for up to 30 years of production. Excavation, crushing, processing, and hauling of materials would occur Monday through Friday between 6:30 a.m. and 5:00 p.m. except on New Year’s Day, Memorial Day, Independence Day, Labor Day, Thanksgiving Day, and Christmas Day. Stacking, loading, and hauling of materials would occur Monday through Friday between 6:00 a.m. and 5:00 p.m. Saturday operations would occur no more than 15 Saturday's per year; no longer than 7:00 a.m. to 3:00 p.m.; no more than one Saturday per month from May 15 to October 15, inclusive. Evening work for special circumstances would occur only 30 work evenings per year, no longer than 5:00 p.m. to 8:00 p.m. The total workforce would include up to 75 employees.
2. Amend the 2009 Reclamation Plan for SCQ to:
   1. Update Reclamation Plan Boundary: SCQ proposes to expand the Reclamation Plan boundary to include portions of adjacent parcels (Assessor Parcel Numbers 351-10-017, 351-10-033, 351-10-039, 351-11-011) located directly to the east and west of Parcel B that are currently owned by Lehigh. SCQ plans to enter into a lease agreement with Lehigh to use portions of these adjacent parcels to extend the highwall along the western face of Parcel B and expand mining operations.
   2. Expansion of Mining and Correct Slope Instability Issues: SCQ plans to expand mining operations along the western face of the existing Parcel B highwall by constructing new benches to a bottom elevation of 860 feet msl in the northern portion of the pit, and 700 feet msl in the center and southern portion of the pit. To achieve a 2:1 horizontal to vertical (2H:1V) cut slopes on the west slope, portions of the west pit boundary would be adjusted farther west to provide area to cut the slopes into native stable material and remove the current, potentially unstable material within the steeper slopes. The quarry floor is planned to have a maximum depth of 700 feet msl, with gently sloping floors that drain southerly and westerly. The bottom of the pit would then be backfilled to 900-feet msl with fill slopes not to exceed 3H:1V overall. The proposed RPA provides for 2.6 million tons of material moved annually with a 30 percent overburden waste factor, for a maximum annual crusher feed of 2 million tons per year for up to an additional 30 years.
   3. Reclamation of Haul Road: SCQ would convert the new Haul Road (Item 1c above) to a Utility Access Road onsite as part of reclamation.
   4. Import of Fill: SCQ proposes to import up to 2 million cubic yards of backfill material over a 30-year period for reclamation.  Fill material is expected to be acquired from regional construction projects.
   5. Stormwater Flow and Settling Basin: SCQ proposes to implement best management practices (BMPs) to direct offsite and non-industrial run-on away from industrial areas and erodible surfaces in compliance with the National Pollutant Discharge Elimination System (NPDES) General Permit for stormwater discharges. Berms, drainage ditches, drop inlets, sediment traps, silt fences, check dams, and straw wattles will be implemented throughout the property to meet this requirement. The run-off from the quarry would be redirected from the existing in-creek Upper Settling Basin to a new settling basin designed and engineered by Bay Area Geotechnical Group (BAGG Engineering) to be consistent with design storm standards in the Industrial General Permit for the expanded mining areas as well as Compliance Agreement and Stipulated Order to Comply and Regional Water Quality Control Board requirements. The new settling basin will be located on Parcel A, directly northeast of Sediment Pond 4. The settling basin capacity is estimated to be approximately 4.4 acre-feet provided that the pond's side slopes are cut at an approximate gradient of 2H:1V and the development access road is raised by 10 feet at an approximate 1.5H:1V gradient. The two water tanks at the current location will be relocated.

3. Zoning Interpretation to allow:

   1. importation of and processing of aggregate, either as part of County regulations governing Surface Mining (§ 2.10.040 of the Zoning Ordinance), or as an Incidental Use to a Surface Mining Operation, as allowed for in County Zoning Ordinance § 2.10.020(B).

      County Zoning Ordinance § 2.10.040 currently defines Surface Mining as “the process of obtaining minerals, such as sand, gravel, rock, aggregate, or similar materials by removing overburden and mining directly from mineral deposits, by open pit mining of naturally exposed minerals, by use of the auger method, by dredging, and by quarrying.”

   2. The application materials specify that SCQ proposes to extract and process 2,000,000 tons of aggregate per year and import and process an additional 1,000,000 tons per year of un-processed aggregate from Lehigh Permanente Quarry. The resubmittal letter more fully describes the requested Zoning Interpretation.