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Construction begins on plant to clean up tainted Flowing Wells water

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A drinking-water cleanup is planned at the site of two contaminated wells in the Flowing Wells area northwest of Tucson.

Construction has begun on a $1 million dual-purpose water-treatment plant that will begin removing arsenic and low levels of two well-known toxic chemicals from two drinking wells in September. The wells serve about 20 to 30 percent of the Flowing Wells Irrigation District's 15,000 customers.

Flowing Wells customers will pay the $600,000 to $700,000 share of the cost needed for arsenic treatment. The state will pay the remainder of the construction cost, according to a statement released by the Arizona Department of Environmental Quality.

A $2-per-month water rate increase that went into effect last September will help pay Flowing Wells' share of the capital costs for building the arsenic-cleanup facility at the treatment plant.

Operating the plant to remove arsenic will cost $150,000 a year, but officials don't anticipate another big water-rate increase to pay for that, said David Crockett, Flowing Wells' superintendent.

Most immediately, the cleanup will allow the irrigation district to resume using the two wells, which were shut down in January because arsenic levels of 32 and 48 parts per billion exceeded new federal drinking-water standards. The new federal standards dropped from 50 to 10 parts per billion in January. But the wells had not been used much in the past five years because either they or the surrounding aquifer contain the once-common industrial solvent trichloroethene and the dry-cleaning solvent tetrachloroethene.

The wells, one on Roger Road and one on Romero Road, lie within an oblong-shaped underground plume of contaminated groundwater stretching from Wetmore Road on the north to about halfway between Roger and Prince roads on the south. The plume hugs Romero Road on both sides.

"There was no treatment available. We didn't want to take a chance at pumping volatile organic chemicals into our system," Crockett said on Thursday.

The arsenic levels in the drinking water should drop immediately, with the plant running continuously. But the toxic chemicals will remain significantly longer. It will take longer than five years and cost up to $53,000 a year for the state to do the cleanup.

The toxin levels in the wells are below federal and state drinking water standards, but the state is removing them as a preventive measure, said Steve Owens, the department's director. The surrounding aquifer has higher levels of the toxins, and authorities don't want the chemical pollution there spreading to other drinking wells in the area, Crockett said.

The treatment system uses three steel tanks, each measuring 12 feet in diameter and 15 feet tall. Two will use a powdery carbon substance to remove the toxins. The third will use a fine-ground iron-based substance to filter the arsenic.

"I'm not excited about the new arsenic standard, but I think the fact that we're getting the treatment plant built is a positive step," Crockett said Wednesday.

The tighter arsenic standards were opposed by many municipal water utilities across the country, who said they were too stringent and would cost too much for local governments to meet. But many scientists and environmentalists said they were needed, and the Environmental Protection Agency ultimately agreed to institute them.