Limestone quarry and cement processing operations in the foothills just south of Los Altos may intensify under a recently submitted draft plan that calls for Lehigh Southwest Cement Co. digging a new 60-acre pit along Monte Bello Ridge.
Lehigh is also hoping to import fill for its main pit, rather than using mining waste already on-site, as proposed in its 2012 reclamation plan. Importing fill, observers said, could result in hundreds of additional truck trips daily.
Cupertino resident Rhoda Fry, who is tracking Lehigh’s operations closely, said the new “reclamation plan” is “significantly different” from its 2012 plan. Her concerns included “viewshed” impacts, increased traffic, air pollution, the digging of a new quarry near vineyards and lack of reserve funds for actual land reclamation.
“The application intends to … lower the ridgeline facing Los Altos by 100 feet,” Fry said last week, “and also not move the (West Materials Storage Area), which is the horizontal line that you can see across the hillside.”
She noted that the quarry deeded the viewshed in 1972, “promising no alteration to the ridgeline.” The 2012 reclamation plan stabilizes the slopes with a buttress, while the new plan “mines and modifies the protected ridgeline,” Fry said.
The 2012 plan calls for moving 48 million tons of mining waste from the 175-acre Western Materials Storage Area to fill the main pit. The new plan proposes importing fill while leaving the existing mining waste in place. Lehigh officials cite environmental concerns involving selenium impacting the groundwater.
“Importing fill would be another source of income for Lehigh, would prolong the process of filling the pit and create more local pollution from trucks,” Fry noted.
She envisioned Lehigh importing fill – soil, rock, sand, broken concrete – from all over the Bay Area, far exceeding its 70,000 annual truck-trip limit imposed by the Bay Area Air Quality Management District.
Santa Clara County officials issued Lehigh a notice of violation earlier this year over unpermitted transport of aggregate to nearby Stevens Creek Quarry.
Los Altos resident Libby Lucas, a longtime water environmentalist, shared concerns about the new plan.
“Up until now, a primary concern with Lehigh has been their cement treatment plant discharges to Permanente Creek,” she said. “After hearing proposed expansion plans, any angst about treatment plant pollutants in drinking water reserves is overshadowed in consideration of volumes of sediment to be released into Permanente Creek watershed by aggressive quarrying of Monte Bello Ridge.”
Lucas fears that quarrying Monte Bello Ridge may generate more sediment than the present creek channel can carry, which would override flood basin conduits before they divert flows, as occurred when Blach Intermediate School flooded in the early 1980s.
“Monte Bello Ridge is said to be protected by a scenic easement, but Los Altos will need a strong legal expert to ensure this is fully adhered to by Lehigh,” she said. “The State Mining Act affords wide latitude to quarrying activity.”
Los Altos Hills resident Kit Gordon said she’s concerned about the nearly three-year delay in Lehigh’s court-ordered restoration of Permanente Creek.
“Before the county considers any other permits for Lehigh operations, especially their new expansion plans, they should move this restoration project forward,” Gordon said.
The cement plant’s longtime presence in the Cupertino hills intersects traditional mining and cement production – naturally dirty processes – with the concerns of homeowners who built and moved into the area decades after the cement plant began operations in 1939.
Fry noted that the Lehigh plant is the top emitter of greenhouse gases in the county. Supporters counter that the plant provides more than half of the cement used in Bay Area construction, which keeps costs down and benefits the economy.
A Lehigh official did not respond to a Town Crier query seeking comment.
Santa Clara County Supervisor Joe Simitian, whose office has been working closely with Lehigh officials, acknowledged Fry’s concerns but noted the new expansion/reclamation plan is far from complete.
He said any hearing before county planning commissioners or the board of supervisors is probably “not this calendar year.”
County and Lehigh officials will be working on the plan in the months ahead, which will include a “thorough environmental assessment,” Simitian said.