Vegas’ Growth Is Gamble for Lake

Las Vegas’ relentless growth has raised concerns that the city’s expansion will send more pollutants into Lake Mead, hurting water quality in the nation’s biggest reservoir and the source of drinking supplies for millions in Southern California and the Southwest.

With each new subdivision in the southern Nevada desert, more wastewater and urban runoff drains into Mead, a sparkling blue national recreation area but also the receptacle for all of metropolitan Las Vegas’ treated sewage.

A wastewater coalition is proposing a solution: a massive pipeline that would take most of the effluent from a wash that now empties into a shallow bay and instead dump it directly into the cold depths of the lake closer to Hoover Dam. There, in theory, it would undergo more dilution and be less likely to feed surface algal blooms.

But some experts fear the pipeline project could simply export the pollution threat out of Mead to the lower Colorado River, where Southern California and Arizona draw water. “It’s not a good situation for those downstream,” said Alexander J. Horne, a UC Berkeley professor emeritus in environmental engineering and part of a team that reviewed computer modeling of the proposed pipeline project.

He and others argue that moving the wastewater outfall several miles south, closer to the dam, will eliminate natural scrubbing that now occurs in the wash and the lake. That could make it more likely that algae-breeding nutrients such as phosphorous will migrate out of Mead and reach the lower Colorado.

Douglas W. Karafa, program administrator for the Las Vegas Valley wastewater coalition that is overseeing the pipeline project, said that while phosphorous levels might rise slightly, they would remain well within water quality standards. “Saying there is a little more phosphorous going out of Hoover Dam doesn’t necessarily relate to anything that is going to happen environmentally,” Karafa said.

The ever-increasing volume of effluent draining out of the Las Vegas Valley makes it imperative, he said, that the outfall be moved from Las Vegas Wash, which carries a steady stream of treated sewage into Mead from the region’s three water reclamation plants.

The daily effluent flow has swelled to 170 million gallons from 40 million gallons in the 1970s. It is projected to hit 300 million gallons by 2030 and 400 million gallons by 2050. There will be so much wastewater that planners want to use it to power an underground hydroelectric plant that would be built as part of the pipeline project.

The flow has eroded the 12-mile wash, cutting deep channels, tearing out wetlands and dumping sediment into the lake that hurts water quality.

Researchers have found that fish living near the wash’s outlet in Las Vegas Bay have lower sex hormone levels and trace amounts of birth control chemicals and other compounds present in the wastewater.

Algae, which can be a pollution problem, has at times reached troubling levels in the bay, probably stoked by nutrients found in the discharge -- a situation expected to worsen as the wastewater flow increases.

To ease the effect on the wash and the relatively shallow bay, the wastewater coalition is proposing a $600-million project that would divert most of the effluent into a 12-foot-wide pipeline nearly 20 miles long. The pipe would extend seven miles through the River Mountains and release the waste into the lake about 1 1/2 miles off Boulder Beach, at a depth of roughly 260 feet.

Designed to encourage dilution and to keep the effluent in an algae-hostile dark layer of the lake, the new outfall would also move the wastewater flows downstream, away from the intakes that Las Vegas uses to draws its drinking water from Mead.

But like Horne, Mic Stewart, the water quality manager for the Metropolitan Water District of Southern California, worries that moving the wastewater discharge to within about 3 1/2 miles of Hoover Dam would leave more phosphorous and other nutrients in the water to flow through the dam to the lower Colorado.

“Even a little bit of increase in phosphorous in the river could stimulate algal growth,” Stewart said.

G. Chris Holdren, a U.S. Bureau of Reclamation lake expert who was on the modeling review team, says the outfall move might even pose a threat to the lake above the dam. “The problems as I see them -- depending on how the discharge eventually gets mixed into Lake Mead -- is a potential increase in the algal blooms in the open part of the lake where it could impact recreation.”

Algae can be toxic, although Mead’s blooms so far have not been. Much of Mead, normally a clear blue, turned a cloudy pea green in 2001 when a giant bloom spread across its western portions. But fish and water quality were not affected.

Still, the 2001 bloom -- the cause of which remains unclear -- illustrated Mead’s long reach. “The bloom was so extensive that it spread throughout the lower Colorado River system ... and even into reservoirs in the Southland region as far south as San Diego, a distance of about 400 miles,” Stewart said.

The best solution to the algae threat, he said, was to increase treatment at the wastewater plants that serve the Las Vegas Valley.

Arizona water officials have not expressed concern about the outfall move. The National Park Service, which manages the Lake Mead National Recreation Area, said it had confidence in the modeling, which indicates the new outfall area would meet water quality standards -- whereas continuing to discharge all the effluent in the wash would lead to pollution problems in Las Vegas Bay.

Erik L. Orsak, environmental contaminants specialist for the U.S. Fish and Wildlife Service, also said that pumping the effluent into a deeper portion of the lake would mean less exposure to trace chemicals for the endangered razorback sucker, a native fish that spawns at the mouth of the bay. “The middle of the basin is one of the best choices [for Mead fish] and certainly has the greatest potential for dilution,” he said. Still, Orsak said he advocates more treatment at wastewater plants before the effluent reaches Mead.

But what is good for the lake’s razorback suckers may not be good for the ones living below Hoover Dam in the lower Colorado, where federal officials recently launched a $626-million restoration program for native fish and plants.

“We may indeed be relocating to some degree the wildlife exposure to sites below the dam,” said Timothy Gross, a research physiologist and toxicologist with the U.S. Geological Survey who has helped document trace amounts of pharmaceutical compounds in Mead fish. “Water quality downstream of the dam is likely to decline -- significantly, probably,” from increasing wastewater flows and moving the outfall.

Gross and other federal researchers began studying Las Vegas Bay fish in the late 1990s, testing nonnative carp and largemouth bass as well as razorback suckers. All three species exhibited lower thyroid function. Both males and females had lower sex hormone levels, and in males the quality and motility of sperm were diminished.

The fish additionally had trace amounts of chemicals -- also found in the Las Vegas effluent and Las Vegas Bay water -- that are derived from birth control pills, antidepressants, antibacterial soap and fragrances.

“Much of what we’re detecting are things that come from sewage outfalls,” Gross said.

While researchers have not definitively proved the cause of the fish hormonal problems, they “in all likelihood are tied to effluent,” Orsak said.

Such compounds have been detected in wastewater worldwide, and regulators are trying to figure out what, if anything, to do about them. There are no clean water standards for them, and conventional sewage treatment removes only some of the substances, many of which are endocrine disrupters.

“It seems to me most scientists agree that it is not a human health issue from a drinking-water [standpoint],” said Shane Snyder, research and development project manager for the Southern Nevada Water Authority, which supplies Mead water to the Las Vegas area.

“It’s more of an ecologic, aquatic-life issue.”

Snyder, who sits on a federal advisory committee examining the matter, said his latest research indicates ozone and reverse osmosis treatments can remove most if not all of the compounds from wastewater streams.

But “the cost of implementing these types of processes can be enormous,” he said. “From the data I’ve seen, I certainly would not advocate vast amounts [of spending] for water treatment or removal of these compounds -- in Lake Mead for certain. I believe there are more important issues that public dollars can go to.”

Karafa also said that while the valley’s wastewater agencies can make some adjustments to improve the treatment all three plants already employ, there are limits to how much they can do without jumping to much more expensive technology that would have its own drawbacks.

Reverse osmosis, for example, would convert a significant amount of the wastewater to an unsavory brine that would have to be disposed of and -- more critically from southern Nevada’s standpoint -- reduce the Las Vegas Valley’s take of Colorado River water.

That’s because Nevada is credited for whatever treated wastewater it puts back into Mead, meaning that in practice it can draw much more from the reservoir than its legal entitlement. Reduce the wastewater returns, and Las Vegas gets less Colorado River water.

At the Clark County Water Reclamation District, which generates a little more than half the wastewater going into Mead, Deputy General Manager Doug Drury said he is slashing the phosphorous output of his plant by fine-tuning the existing treatment process. Given that, he argues that more wastewater doesn’t necessarily equal a nutrient problem for Mead or the lower Colorado.

“I don’t see us being stagnant in treatment of phosphorous,” he said.

“I believe we’ll have to lower it and lower it.”