Updated

Officials overseeing a tiny farming community in central California are expected to make a decision Tuesday on the proposed expansion of the largest toxic waste dump in the West of the U.S. amid growing concerns about a spike in the town's number of birth defects.

Chemical Waste Management Inc. wants to increase the size of its 1,600-acre facility near Kettleman City, a town of 1,500 about three hours north of Los Angeles in the San Joaquin Valley. The proposal is slowly moving through a permitting process that includes local, state and federal regulators.

It faces a Tuesday vote by the Kings County Board of Supervisors. Community members have been urging the board to reject the proposal after discovering an alarming increase in birth defects and infant deaths.

Of 20 children known born in Kettleman City between September 2007 and November 2008, five had a cleft in their palate or lips, according to a health survey by activists. Three of those children have since died. Statewide, clefts of the lip or palate routinely occur in fewer than one in 800 births, according to California health statistics.

Besides these health problems, activists point to the high asthma and cancer rates in this largely Spanish-speaking farming community.

"Why in a town of 1,500 were five babies born with clefts? It's totally unacceptable," said Maricela Mares-Alatorre, 37, who heads People for Clean Air and Water. "Who's responsible? What's happening?"

The dump's owners support a health study and have even offered to pay for one, but say there's no evidence linking the facility to the birth defects. Other potential culprits are pesticides sprayed on nearby fields, discolored drinking water and exhaust from Interstate 5, the West Coast's major north-south highway, which borders the town.

After years of fighting Chemical Waste, activists have become distrustful. They have accused the company and public agencies of holding meetings at inconvenient times and places and refusing to translate documents into Spanish.

They have also threatened to sue if the supervisors approve the project.

Chemical Waste is Kings County's biggest business, contributing as much as $3 million a year to the county's general fund. Kettleman City community leaders complain that little of the money comes back to the town, which has no sidewalks or stop signs.

About 400 truckloads of waste are hauled to the dump each day. In 2007, the last year for which complete statistics are available, that meant more than 3 million pounds of lead compounds, nearly 2 million pounds of asbestos and more than 118,000 pounds of arsenic, according to the Environmental Protection Agency. It's the state's only facility that accepts cancer-causing PCBs.

Most of the waste comes from California, with smaller amounts from other states and even Mexico.