MODIFYING WELLS SHOULD LOWER ARSENIC COUNTY RESPONDS TO TOUGHER STANDARDS.

Byline: Charles F. Bostwick Staff Writer

LANCASTER - Facing stiffer federal restrictions on a naturally occurring toxin, Los Angeles County will spend more than $525,000 modifying five Lancaster-area water wells to reduce their intake of arsenic.

The county Board of Supervisors voted Tuesday to seek a construction company to seal off the five Los Angeles County Waterworks District wells' deepest levels, where arsenic concentrations are highest.

``We are blocking that lower portion of the wells,'' said Dean Efstathiou, county Department of Public Works assistant director.

Waterworks District water is safe to drink, he said. Although some individual wells have higher arsenic concentrations, he said, the overall average is lower than the limit that takes effect in January of 10 parts per billion.

The arsenic limit in drinking water has been 50 parts per billion for more than 50 years.

Arsenic in Antelope Valley wells - and in most other places in the United States, especially the West - does not come from industrial pollution but occurs naturally in the rock and soils, officials say.

The county revealed in 2001 that 11 of 28 waterworks wells that supply homes and businesses around Lancaster tested at higher than the impending limit. Those wells' water is blended with California Aqueduct water and with water from wells with less contamination to lower the average, county records show.

A deadly poison at higher concentrations, arsenic at low levels in drinking water has been linked to cancer of the bladder, lungs, skin, kidney, nasal passages, liver and prostate, experts say.

The EPA estimates that about 4,000 water systems - most serving fewer than 10,000 people and most in the Western United States - have water contaminated by arsenic at concentrations higher than the 2006 federal standard.

The amounts of arsenic involved are minuscule: The new federal standard of 10 parts per billion is equivalent to about 10 drops in 13,000 gallons of water. The present standard of 50 parts per billion has been in place for 49 years.

The EPA estimated that reducing arsenic from 50 parts per billion to 10 parts per billion will prevent 20 or 30 deaths a year nationwide from lung and bladder cancers.

Deeper wells tend to have the higher levels of arsenic in the Antelope Valley, county officials said, but they also produce more water than shallower wells.

The five wells to be modified are about 1,200 feet deep. They will be modified to close them off below a layer of clay that lies about 500 feet to 700 feet underground.

The modification will reduce the wells' water output by nearly one-third, but the waterworks district has sufficient alternative sources of water to make up the difference, Efstathiou said.

The work is expected to begin in November and be finished by June.

Wells provide about 40 percent of the water supplied by the county waterworks district, which covers most of Lancaster and other areas around the Antelope Valley.

The rest of the water comes from the California Aqueduct, which has no detectable levels of arsenic.

Charles F. Bostwick, [phone]

chuck.bostwick(at)dailynews.com