RECLAMATION

Dumbarton Quarry: Evolution of a Mine and Its Public Benefits

By Dave Brown, Principal/President, Benchmark Resources

Before: This December 2008 view shows the operation at the final stages of mining. The plant site sits aside the quarry.

On August 28, 2021, CalCIMA Member DeSilva Gates’ Dumbarton Quarry opened its gates to new traffic - motorhomes and campers. The first phase in transformation of the site to the Dumbarton Quarry Campground regional park was completed with an RV campground, camp store, 200-seat event amphitheater, playground, and bicycle paths and hiking trails. The East Bay Regional Park District will manage the site for public recreational use and heralded the occasion as “the first public park opened in the region in decades.”

Reclamation of the quarry for a campground was not the original plan.

Dumbarton Quarry began its life in 1957 like most quarries, simply as a local source of quality rock located in close proximity to regional construction projects. Over the years, critical infrastructure in the East Bay and beyond were built with rock from the quarry. Dumbarton Quarry supplied local aggregates—shortening haul distances and reducing air pollutants and greenhouse gas emissions long before there was environmental vernacular for these benefits. The quarry provided material for repairing damage caused by natural disasters like the 1989 Loma Prieta earthquake and the 1991 Oakland Hills fire when considerations for response and resiliency to environmental disasters were just beginning to become recognized as important elements of community planning.

Federal and state environmental laws, including the California Surface Mining and Reclamation Act (SMARA), and changes in regional and local land use plans all appeared after the quarry began its operations. For compliance with SMARA’s reclamation plan requirements, reclamation of the site with a lake and park was proposed.

After: This aerial image was taken in January 2022. The first phase of park development (foreground) is complete. Quarry backfilling operations (background) continue and will be subsequently developed for additional drive-in and walk-in campsites, group camping, and trails.

Opponents objected and wanted the quarry immediately closed, but the plan was eventually adopted. However, subsequent changes in water quality regulation, limitations in surface water availability, and other unforeseen obstacles complicated execution of the plan; it needed a new vision.

Backfilling the quarry became a new objective that had not been previously envisioned. A costeffective and nearby location to accept excess soil and inert material generated from construction activities had become recognized as an important regional need. Fill from development such as underground parking structures needed a legal and environmentally responsible destination. With excavation completed, Dumbarton Quarry was perfect. Backfill tipping fees would include an allocation towards park construction. The reclamation plan was revised with multiple objectives pursued: Quality of accepted fill based on hydrogeologic connectivity to aquifers, fill that could be compacted as needed for subsequent public surface uses, revegetation to meet soil stabilization needs and to be suitable for public use and open space areas, and timing and phasing to allow for development of public use areas as soon as possible while providing for safe and efficient completion of fill placement in remaining areas of the site. Although objections were again voiced by some, cooperation between stakeholders gained support and approval of the new plan. Backfilling was projected to require 15 to 20 years, but the strong demand for disposal of excess fill reduced that to less than seven. A further refinement to the plan was made in 2018 allowing for increased fill to restore the site’s topography similar to the pre-mining hillside and with the added benefit of sheltering campground areas from the wind.

The vision and flexibility demonstrated throughout Dumbarton Quarry’s operations are essential to mine and reclamation planning. Had operations ended prematurely, the full site benefits of aggregate resources, beneficial reuse of excess soil, and the extent of development as a significant regional park would not have been possible. Not every quarry can be backfilled and not every mine site can be reclaimed as a park, but public and agency recognition and acceptance of mines as an essential land use may provide unforeseen future benefits. n

David Brown has a 40-year career in environmental planning and permitting. He is president of Benchmark Resources, a firm specialized in mine planning, permitting and regulatory compliance, with a statewide presence.