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He's pulled on rubber boots and stepped gingerly out onto the cracked, miles-long cake of sludge that had been mucked out of the Arizona Canal and piled on the canal-side path near 51st Avenue. At first, the top layers squish beneath his footsteps with the sponginess of brownies that aren't quite ready to come out of the oven. But with the next step, he's sucked under, and has to lean hard on a shovel to keep from sinking in over his boots.
Each winter, SRP drains the canals and dredges out more than 7,000 cubic yards of sludge at a cost of a quarter-million dollars or so.
The sludge is a by-product of the City of Phoenix's water treatment plants, a mixture of dirt and disease that has been coagulated with the help of aluminum sulfate, or alum. Unlike the practice at most of the country's water treatment facilities, in Phoenix the aluminum-tainted sludge is dumped right back into the water, where it floats downstream to the next water treatment plant in concentrated flows, or "slugs."
Since 1988, SRP has been trying to stop the dumping, but with little success, so SRP workers shovel it out and lay it along the canal, three to four feet deep, ten to 15 miles at a time.
Phoenix city ordinances will not allow SRP to truck it wet through the streets for fear that it will leave messy, muddy trails through the neighborhoods. Even if SRP could truck the wet gunk, no landfill would accept it because its free-flowing liquid could cause other city-dump dirtiness to leach into the soil. And if SRP found its own site for dumping the wet glop, it would probably need an aquifer-protection permit from the state Department of Environmental Quality to do so; water from the sludge could carry aluminum or microbiological freeloaders down into the water table.
And so the sludge sits and stinks on the canal banks for four to six months, the time it takes to dry enough to be accepted at a landfill.
"Every year we get complaints from residents because it smells," says Cherrington. "No matter where we put it."
Canal joggers, bikers and dog walkers hate it. It's hampered the city's plans to use the canalside as a recreation area, because one bank has to be kept free for the annual sludge dumps.
Aside from aluminum--a metal suspected to contribute to Alzheimer's disease--the sludge may contain fecal coliform, a feces-based bacterium; giardia, a parasite that causes dysentery; and a host of other contaminants. Neither SRP nor the City of Phoenix will admit to having done a microbiological analysis of the sludge, perhaps for fear of what might be in it, and the remediation that they might have to make.
Meanwhile, little boys play in the muck, which is easily accessible to anyone walking along the canals. Some local communities like to sprinkle the talcumlike dried sludge on their park department baseball-diamond infields. Former mayor Paul Johnson used a few truckloads to fill a wash in his backyard, though his wife complained it stank of fish.
As revolting as the sludge is on dry land, however, it may be more troubling in the water.
SRP and the cities of Tempe and Chandler worry that the contaminated outflows from Phoenix water treatment plants carry high levels of an intestinal parasite called cryptosporidium, a chlorine-resistant protozoan that causes serious diarrhea and flulike symptoms in healthy folks--and kills people who have AIDS or who are undergoing chemotherapy for cancer or who have otherwise compromised immune systems.
"Our biggest concern now is the health issue," Cherrington says.
Cryptosporidium, or "crypto," as it is affectionately called, comes from livestock and wildlife in the watershed. Their contaminated stool washes into the Salt and Verde rivers and then on into the SRP canals that provide drinking water for much of the Valley.
Officials at Valley water treatment plants claim that they successfully filter out the cryptosporidium.
"That's garbage," says Dr. Ken Fisher, a Phoenix physician who treats AIDS patients, "unless the City of Phoenix is using a very sophisticated high technology, only a specific microfilter that will filter it out. And you'd have to use chlorine in levels higher than you'd use in your swimming pool to kill it."
Fisher recommends that his patients boil their water.
Only four cases of cryptosporidiosis, as crypto infection is called, were reported from Maricopa County to the Arizona Department of Health Services in 1994, the first year that such statistics were kept by DHS. That rose to 17 in 1995. But Dr. Fisher claims that in his clinic alone, there are more than 30 AIDS patients afflicted with cryptosporidiosis.
Logic says that at least some of those crypto sufferers contracted the disease from tap water.
Science does not yet know just how much crypto it takes to make you sick. Nor does anyone understand how it travels. In fact, there is no good way to measure it, in raw or treated water.
But because sludge is the end product of the filtering process, that is where the cryptosporidium most likely ends up, this time in concentrates that downstream water plants don't want to deal with.