Lake Powell is under extreme stress! Snowpack is over double the average for this date. Rivers are running about average for this date, with twice as much as normal to come. Lake Powell is now the highest it’s been in five years, and five feet higher than it got last year.
Las Vegans woke up this morning to this scary headline in the Sun:
Meanwhile, over at the Lake Powell water level database, the reservoir upstream from us is only half empty, has been delivering roughly the same amount of water per year since the dam was built a half century ago (with the exception of a couple of flood events, and today holds more than Lake Mead does. The 27 reservoirs above it are more than 80% full.
I should’ve taken pictures but didn’t. This morning, the Ward 2 team toured the water reclamation project located at Ft. Apache & Cheyenne.
One of the more important, yet rarely spotlighted functions of city government is the sewer system. This water reclamation plant is a joint project within the sewer system that probably saves more than it costs, thus making the provision of collective services more efficient.
The suburban water reclamation facility lies blending into the background on the NW section of Durango and Cheyenne. Very cleverly designed, it skims off the cleanest portion of the “sewage stream” and treats it to legal purity. The clean water output of the complex process there (I’ll get into it with you, below) is purchased by the many golf courses from the project site all the way south to Canyon Gate. There’s a lot of courses. They use it to water their landscaping and pass the costs along to their golfers, and the Water Authority has revenue.
The theory is that the cost of running the water reclamation project at Durango & Cheyenne is less than the cost the authority would have spent on electricity pumping all that golf course water up the more than one thousand foot incline to the west edge of the valley, minus the new revenue from golfers.
It cost a bunch to build – the City borrowed money to do it, but with the rapid rise of NV Energy electricity (7% increase at my house, per kw H, June 2014 over last year) my feel is that the cost of running the plant plus the interest on the loans is less than the cost of the electricity if you were to pump it all the way up there.
So the first step is they turn off the intakes during the night. At night, the sewage stream tends to be lesser and “nastier” – primarily because many of us are sleeping and that’s when water softening systems are set to back-flush their filters automatically, and the output sent down the sewer is very salty, so they don’t take from the stream during overnight hours.
That duty (and all others!) falls on the much larger main water reclamation plant on the west bank of the Las Vegas Wash, south of city limits. There, all the water from the valley’s sewer collection system is purified and released into the Las Vegas Wash, where it drains into Lake Mead, probably a little too close to where we take Lake Mead Water back up, though its cleanliness is actually very closely monitored. (Google news “epa cities sewage”)The Water Authority gets a “return flow” credit for these gallons, which means they can increase one-for-one the amount of water they take out of Lake Mead into pre-distribution sanitation.
Meanwhile, back at the northwest’s Water Reclamation facility, when residents get their showers going at dawn, the intakes are there to run incoming gallons through a slowly moving mesh grate that separates out anything smaller than a quarter. This is the worst part for folks queasy about this kind of thing. Lots of things are larger than a quarter.
Past the moving mesh, the water enters a system of centrifuges that take out anything else solid. Next, the water swirls around for a long time with a living colony of bacteria that eat tiny stuff bad for us, and reproduce. They swirl in a manner a little similar to the river that runs around Wet N Wild, always with a current that pushes folks along. They eat stuff bad for us people, age and reproduce.
A team of biologists works at keeping this living colony (for which the water is food) at the right equilibrium of young bacteria and old bacteria, as the circle of life becomes one with the swirl down your drain. At the end, the end-of-life bacteria fall to the bottom of the tank, and are eliminated.
The water of the top of this swirl is getting fairly clean now, and its surface layer is skimmed over a special spillway, having risen to the top, literally. This pretty-water stream is then run through a physical micro-filtration system, which takes out any fine particles that have made it through. Once a day or so, a machine comes along and pushes water backwards through the filters, directing this dirt-laden flow away, making the filters ready for another automated day filtering tiny particles from the water stream. Entering this process, the water flow looks notably clear, already.
After physical filtration, the water is pumped into a long labyrinth of channels where the water mingles with added chlorine, to a certain percentage, for 90 minutes. This kills all pathogens that might have made it through the increasingly fine filters.
Throughout, the city plant chugs along, adding to the reservoir 125,000 to 250,000 gallons of golf course water 16 hours a day, plus or minus. The golf courses can turn their pumps on and fill their water hazards, which in turn will pressurize their sprinklers, whenever they want. And the water authority’s distribution system to the golf courses is mostly gravity powered.
I’ll see if I can hunt down the economics of the deal – how much less it costs to run the plant than it would to pay for energy to life so many gallons of water up to the west edge of the valley.
In the meantime, the treatment of our sewage – turning it legally pure and releasing it back to the Colorado – is wickedly expensive. Some analysts contend it is what has brought North Las Vegas to its knees. They used to have Las Vegas treat their sewage – it didn’t cost much more, and you could divide the cost over many more thousands of people. They they decided to build their own plant. Essentially, this doubled the overall cost to get the job done, and thus individual per-citizen cost doubled. NLV revenue did not increase – hence their fiscal crisis.
1983 was not that unusual. It wasn’t unusual for the US Dept. of Reclamation to fail to hit the target for how full to let Lake Mead get. What was unusual was that it was so obvious.
You see, if your target is to fill Lake Mead to the 65% level, and you make a mistake and it ends up filled to 80%, no one but your supervisor will be able to tell. The casual observer can’t see the difference.
But when Lake Mead is already 90% full and your target is 95% but it actually goes to 101% – well, that’s what happened in 1983. The video shows water coming over the spillways at the top of the dam. Bureau of Reclamation actually placed six-foot tall plywood extensions to make the spillway even higher, to stop the spectacle.
I was reminded of all this as I checked on the snowpack above Lake Powell. We’re only a third of the way through the water year and still holding above average, and much better than recent years past. We are reminded of the folly in trying to forecast each year based on last years’ activity, even for the “experts”.
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