Hanson Permanente Cement Inc, owners of Lehigh Cupertino cement plant, has agreed to pay a US$2.55m penalty to settle a federal suit and install a US$5m wastewater treatment facility after dumping toxic wastes into a creek that feeds into San Francisco Bay.

Lehigh’s cement plant and limestone quarry, located in unincorporated Santa Clara County west of Cupertino, had discharged on a daily basis millions of gallons of quarry process water and storm water polluted with excessive amounts of selenium and other toxic metals into Permanente Creek in violation of the company’s permits from at least 2009 to 2014, federal officials said.

Lehigh Southwest Cement Co, which runs the plant, addressed the firms’ violations of the federal Clean Water Act, the US Department of Justice, Environmental Protection Agency and California Attorney General’s Office announced Wednesday.

Under the settlement with federal and state officials, Lehigh must build an advanced wastewater treatment system to significantly cut back the release of selenium and other toxic metals into the creek.

Lehigh, which has already installed an interim treatment facility, plans to complete a permanent one by 2017, make improvements to remove sediment from its storm water runoff and spend US$5m overall to comply with federal standards, according to officials.

Due to the toxic materials that flowed from the plant, the creek is listed as impaired, or too polluted to meet cleanliness standards set by the Clean Water Act, according to federal officials. The creek is considered an important habitat for the California red-legged frog, a species endemic to the state that is designed as threatened under the federal Endangered Species Act, the officials said.