"There is no statistical difference between the upstream locations and the downstream locations," says Bob Hollander of the Phoenix Water Services Department.
The EPA approved the findings, but Phoenix's municipal neighbors are still shaking their heads over the unsophisticated results of the crypto study.
"It's just a snapshot," says Barb Olivieri of the Tempe Water and Wastewater Services Department. "My opinion is that it's just not a complete test, not enough work done."
SRP officials are seething.
"You need to have an extended sampling period of one or two years to do a truly defensible risk assessment of crypto exposures to downstream users," says Kevin Wanttaja, an SRP engineer.
And, Wanttaja and Cherrington point out, crypto poses the greatest problems during the spring as snow melt washes through the grazing lands upstream and the water is at its highest turbidity levels. Phoenix tested during the dry months of September, October and November, when the waters weren't running.
SRP also questioned why Phoenix sampled backwash waters and sludge in the canal, but never actually sampled the sludge in the water treatment plant itself. In the Phoenix data, there are occasions when crypto was detected going into the plant, but it doesn't show up later either in the backwash or the sludge.
In a letter to New Times, SRP officials wrote, "If the [City of Phoenix] sampling program did not detect higher concentrations of oocysts in the canal from the sludge discharge, then the method of sampling should be closely examined because the oocysts don't evaporate or magically disappear."
At the very best, it is nearly impossible to detect crypto in the first place, and then, according to Erik Olson at the Natural Resources Defense Council in Washington, D.C., it is more common to find dead or empty oocysts than live, viable crypto protozoa.
"Generally, even the best labs in the country will find maybe 10 percent," says Olson. "So if you find one, you can assume there are nine others. And the second thing to point out is that in Las Vegas, they had a major outbreak of the disease linked by the CDC to their water supply, and they've never found crypto in their water supply. It's a pretty hard organism to detect."
Besides being difficult to detect, crypto is not evenly dispersed through the water as dissolved contaminants usually are. It does not dilute--consider that Milwaukee's plague floated out of the vastness of Lake Michigan. Crypto travels in unpredictable waves, and one could sample the water an hour before or an hour after it passes by and not detect it.
In March 1995, for example, the crypto count spiked at a San Francisco testing site, going from one oocyst per 1,000 gallons of raw water to 324 in just 24 hours. A day later, it dropped back to low levels as suddenly as it had spiked.
What worries local water department officials is just such a spike.
"We think that an argument can be made that a slug discharge is quite different from the way one might normally receive cryptosporidium," says George Selvia, public works director for Chandler. "If you get one big slug, it concentrates the cryptosporidium and increases the likelihood of it being problematic for us. We just don't want to see our risk increased as a consequence of any upstream discharges."
The risks just aren't known.
Before the results of the Phoenix study were revealed, the EPA's Catherine Kuhlman, who is in charge of issuing permits to the Phoenix water plants, told New Times, "If they say there's a crypto problem, there's a problem. But if they say there's no problem, we may still have a problem."
Rightly or wrongly, Phoenix and Mesa don't think they should make a decision until the problems are proved.
"We're just now getting to the point where we can detect crypto," says Bill Haney, assistant public utilities manager for Mesa. "Until we get to a point where we know the true health risks, it's difficult for us to take a position."
Phoenix, on the other hand, has taken the position that crypto is not going to be a problem. The Phoenix Water Services Department is one of the most capable and sophisticated departments in the country. If it had wanted to do a thorough study of cryptosporidium, more samples would have been taken. Tests would have been run during the wet season, when crypto poses greater threats. The sludge would have been analyzed right in the plant, instead of downstream.
And the results might not have been what the City of Phoenix was looking for.