Moore than 25 years after a cancer-causing chemical was found in some Scottsdale drinking water wells, officials say the treatment mechanisms are finally all in place to clean it up.
Next week, Scottsdale, state and federal officials plan to announce the completion of a cleansing system to tackle one of the largest groundwater cleanup projects in the United States.
Even so, it’s expected to take between 30 and 50 years to clean all the contamination in the Indian Bend Wash Superfund site, said Jamey Watt, a remedial project manager based in San Francisco with the U.S. Environmental Protection Agency.
A chemical called trichloroethylene, found to cause cancer, has spread to groundwater in a 13 square-mile area in Scottsdale and Tempe, Watt said. Three companies — Motorola, GlaxoSmithKline and SMI Holding — have been assigned the lion’s share of the responsibility for the pollution.The chemical was used to clean circuit boards, he said.
“A lot of the contamination is a result of industrial processes they had back in the 1960s and 1970s,” Watt said.
In 2002, a court ordered Motorola and other companies to pay $61 million in a class action lawsuit to about 22,000 south Scottsdale residents and to people living in parts of Phoenix for medical monitoring, personal injuries and property damage. Seven Maricopa County residents had sued the companies in 1992 for improperly disposing of TCE since 1957, creating two plumes in Phoenix and one is Scottsdale.
About three-quarters of the Indian Bend Wash contamination is situated in Scottsdale, covering an area from McDonald to McKellips roads, between Pima Road and 68th Street.
Constructing four water treatment plants for the northern portion alone, not counting the cost to clean up soil across the entire site and groundwater in the southern portion, has been estimated at more than $80 million to date, Watt said. That cost, and the ongoing cleanup costs, have been borne by the responsible companies, he said.
EPA spokeswoman Wendy Chavez said the treatment system is capable of cleaning 5.8 billion gallons of water a year to drinking water standards.
“This is a huge accomplishment. It’s one of the larger pump and treat sites in the nation,” she said. “Now, we’re just going to continue to pump and treat.”
Mike Montgomery, section chief of the EPA’s Superfund program, said the Indian Bend Wash site is unusual in that the treated water is sent into Scottsdale’s drinking water supply.
“There are a lot of backup systems to make sure that contaminated water is never served. There are a lot of safeguards,” he said. “It just wouldn’t make sense to treat that volume of water and dump it into the Salt River. It would be a waste of water in an area like this.”
The highest concentrations in the spill have been measured at several hundred parts per billion. The government’s standard for drinking water is five parts per billion, Montgomery said.
“Relative to other sites, that’s not very high,” he said.
He said spills of TCE are relatively common, but the use of the chemical these days is not. In the past, before the federal government regulated the disposal of TCE, companies often stored it in cisterns or in surface pits.
“It’s pretty common. It was a standard industrial solvent for years,” Montgomery said. “It was usually from underground tanks that might have leaked or were overfilled.”
Growth in north Scottsdale has contributed to the spread of the contamination, he said. As more groundwater was pumped for use north of McDonald Road, the plume began to creep northward.
“Water gets pulled in whatever direction it’s being pumped. That’s one of the things that’s made the cleanup in the north more complex than in the south,” Montgomery said.
A treatment plant at Miller Road and McDonald Drive was installed in the mid-1990s to arrest the plume’s expansion, he said. In drinking water wells north of the site, TCE has been detected, albeit in quantities deemed acceptable by the federal government, Montgomery said.