Lehigh Southwest Cement Co. has until August to address the unauthorized discharge of mining waste into Permanente Creek, which flows through Los Altos and Mountain View.
San Francisco Bay Regional Water Quality Control Board and Santa Clara County officials discovered the pollution during inspections of Lehigh’s Yeager Yard conducted in April and May, according to notice of violation letters the water board and county sent the company in June and July. The yard, located in the foothills of Santa Clara County west of Cupertino, is used to store soil and rocks excavated from the nearby limestone quarry for future use as cover material. The creek is southeast of the yard.
Inspectors observed “significant” fissures and cracks on the yard’s slope, which led to landslides, and wasterock in the creek, wrote Lisa Horowitz McCann, water board assistant executive officer, in a July 9 notice of violation letter to Lehigh.
Wasterock is a byproduct of mining limestone, an ingredient of cement.
“The discharge of inert wasterock creates a condition of pollution via sedimentation of the creek that adversely affects beneficial uses,” McCann wrote. “However, we are also concerned about potential impacts from leaching of metal(loid)s from the wasterock, particularly selenium. According to data submitted May 21, 2019, seeps from this slope contain elevated selenium concentrations.”
Selenium is a naturally occurring chemical element that is nutritionally essential to animals in small amounts but toxic at high concentrations, according to the U.S. Environmental Protection Agency.
A lab analysis of metals within samples collected from the Yeager Yard slide area revealed 8.9 micrograms of selenium per liter, which exceeds the 8.1 micrograms per liter allowed by a water board water quality protection permit.
“So 8.9 is not that much higher than 8.1, however, that’s not a location where there should be noticeable amounts of water seeping or flowing into the creek because they’ve been containing the drainage, treating the drainage water and have authorized discharges at certain points into the creek,” McCann said in an interview with the Town Crier last week.
There is not an immediate threat to drinking water, which is protected by buffering, but aquatic life in and around the creek, including fish and frogs, could be affected, McCann said.
In addition to the water board’s water quality protection permit, the discharge violates county zoning ordinances and the California Code of Regulations. Penalties for failing to take specified corrective actions could include fines and criminal and civil prosecution; the water board set an Aug. 30 deadline and the county set a series of deadlines beginning June 28 and ending Aug. 14.
Heavy rainfall the Bay Area experienced between October and April caused the erosion, which Lehigh reported to regulators in a timely manner, according to a statement the company provided to the Town Crier last week.
“Now that we are in the dry season, Lehigh is in the process of implementing more permanent measures recommended by experts and previously discussed with the Regional Water Board staff to prevent future occurrences,” the statement said.
Measures Lehigh has taken to stabilize the Yeager Yard include installing drainage controls and using silt fencing and erosion control “blankets,” reported Erika Guerra, Lehigh’s environmental director, in a May 16 letter to the county.
The Yeager Yard discharge is just one of several problems Lehigh must address to appease regulators. In August, Santa Clara County officials issued a notice of violation after the company graded a utility haul road beyond agreed-upon boundaries. An administrative citation and notice of violation from Cupertino officials followed in May after Lehigh expanded the road without city permission. Both violations are noted in a July 3 letter Cupertino City Manager Deborah L. Feng sent to Robert Salisbury, a senior planner with the county, to justify why the county should deny a Lehigh application to amend its reclamation plan.
With the amendment, Lehigh hopes to transfer mining aggregate to the Stevens Creek Quarry in Cupertino and to import up to 1 million cubic yards of construction soil each year to backfill the company’s north quarry and prevent the creation of a pit lake, according to the company’s application, which was submitted in May.
Lehigh is also proposing to lower the Permanente Ridgeline by approximately 100 feet along an estimated 3,000 linear feet of ridge. In addition to facilitating the recovery of more limestone, company officials said the project will stabilize areas of erosion on the north quarry wall and improve the aesthetic appearance of the ridge and quarry. First, however, the County Board of Supervisors must consent to update a 1972 ridgeline easement.
Some observers worry the amendment will lead to increased truck traffic as well as mar the view of communities to the north, including Los Altos and Los Altos Hills.