Cupertino's Lehigh Southwest Cement Company has agreed to cut discharges of toxic water pollutants into Permanente Creek, which runs through Los Altos and Mountain View the bay.

The company also will restore a damaged section of the creek under the terms of a settlement with the Sierra Club, which had asserted in a lawsuit that Lehigh sent into the creek millions of gallons of polluted quarry water with elevated levels of selenium and other pollutants.

"These wastes act similar to coffee grounds, clogging Permanente Creek and continuously discharging a brew of harmful chemicals into its water," according to Sierra Club attorney Reed Zars.

Lehigh's quarry and plant produce more than half of the concrete used in the Bay Area.

Pollution is created when the companies mining exposes disturbed rock to rain and groundwater. This water flows into a pit, then through a pipe into Permanente Creek.

As part of its restoration, the company will build a fish ladder, remove mining-related sediments and improve nearby hillsides.

A riparian habitat that is home to red-legged frogs, deer and more than 125 species of birds and other wildlife, the 13-mile creek descends the east flank of Black Mountain and flows into the Mountain View Slough, near Shoreline Park. Pollution has diminished its capacity to support fragile species like steelhead trout, and the state and federal governments have listed it as an "impaired water body."


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"We are very pleased with the conditions of the settlement," said Dyan Whyte of the San Francisco Bay Regional Water Quality Control Board, which this summer plans to set more stringent permits for the plant. "We think it will go a long way to improve and protect water quality."

The lawsuit, filed in December 2011, was scheduled to go to trial in federal court this summer. The agreement is subject to U.S. Environmental Protection Agency and federal court approval.

"We are pleased that the company and the Sierra Club were able to work collaboratively on resolving the litigation," said Kari Saragusa, president of Lehigh Hanson's west region.

"We started from a common baseline ... to restore Permanente Creek in a manner that is environmentally sound and, importantly, scientifically valid." The settlement will help the company accelerate its restoration work, including erosion and sediment controls, he said.

Contact Lisa M. Krieger at 650-492-4098.