The news reports this morning were talking about how the Rim Fire is now threatening to dump tons of soot into the reservoir that supplies 85% of San Francisco’s water. How big of a problem is this? Could the soot be filtered out of the water? Could it be filtered out using equipment that is already in place? Or are we facing the prospect of a major metropolitan area suddenly losing all drinking water for weeks (months?) to come?
Oops! I meant to put this in GQ. Can a Moderator move this for me?
Surely, Shirley.
Worst case scenario is actually worse than that; in addition to 85% of the water, a significant portion of the Bay Area’s electricity is provided by hydroelectric plants in the area that are threatened by the fire.
If the water gets unsafe to drink, they’ll have to filter it, although we do have a six-month supply on hand. So, they haven’t started water rationing or brown-outs yet.
This probably sounds stupid to ask this, but it’s hard to see how the fire threatens the hydroelectric generators. Most pictures of such installations show the generators buried into a concrete dam assembly, with a cleared area around it. Forest fires can’t burn through reinforced concrete.
The transmission towers might be threatened, but though are usually cables mounted on steel towers.
Frankly, the only ways I can see it threatening the dam is either the hot fire can get to those yards full of power conversion equipment, or that the smoke from the fire could make the dam uninhabitable.
Even in that scenario, they could probably control it remotely if the systems are wired that way.
If Hetch Hetchy gets enough ash it could cause the turbines to clog, or do them damage, so they may have to shut down electricity generation until the water clears.
It sound stupid to ignore it, too. I doubt if the dam & generator designers considered a serious forest fire in their plans, just like the Fukushima nuclear plant designers didn’t consider being located near the ocean in an active earthquake zone as being a concern, either.
My understanding is that the Hetch Hetchy reservoir only provides electricity to City of San Francisco facilities; I don’t know what this includes, but it might include the electricity for Muni (including the Metro streetcar/subway system as well as electric buses) and for the cable car cables. I don’t believe if this were to be turned off it would be anything like a general brownout. And they might be able to switch over to the same PG&E power that everyone else uses. It would be expensive for the city (oh, the property taxes) but not too bad if it didn’t go on for very long.
The water thing is much more potentially disastrous. I have heard that there is no filtration currently in place because this reservoir’s water consists of “virgin” rainwater and snowmelt, pure enough to drink without filtering. And it’s not just drinking water, it’s water for toilets and showers and everything.
Serious stuff.
Roddy
Maybe you could get Jim Inhofe to come and explain that this whole thing is a fiction.
Yeah, if my toilet water isn’t pure, I’m not sure I can properly function, and might become constipated.
Ashes to asses, eh?
Thank goodness my toilet water comes from Lake Michigan.
That’s one of the reasons they don’t allow swimming in Hetch Hetchy. And I can tell you that water is damn inviting when you’ve been out all day on the (mostly unshaded) trail that runs alongside it.
It’s not so much the generators as the transmission lines that are at risk. They have already shut down two of the three hydroelectric power station transmission lines to San Francisco. I’ve seen conflicting reports that this was due to damage to the lines, or the desire to protect firefighters who would otherwise have to worry about live wires around them.
After one of Arizona’s may forest fires (a few years ago), there was a torrential rainstorm that washed a tremendous amount of debris into the lakes that are used to provide water for the Phoenix area. The water had a distinct smokey taste for awhile, but was never declared unsafe to drink.
News stories also mention that the SF water system is linked with East Bay MUD and the Santa Clara Valley Water District. They are prepared to draw on those local supplies as well, although that would undoubtedly put an extra strain on those systems. EBMUD probably has the best water in the Bay Area.
Looking at the news articles, the only person I’ve seen that appears to be trying to make the ash fall out as a big problem is a guy from Restore Hetch Hetchy, who I suspect has a bit of an agenda (maybe to restore Hetch Hetchy?).
I think what’s going on based on the statements from people from the utility is that if the amount of ash suspended in the reservoir water reaches a certain limit they may need to filter the water using existing filtration facilities they do have but don’t usually use on water from Hetch Hetchy. But at the present they haven’t reached that limit and plus there’s a 6-month supply of water in downstream reservoirs as well. I would imagine that the ash will eventually either wash ashore or settle out on the bottom, so there’s only a threat so long as fresh ash is landing on the reservoir. In other words, it’s not like all however many hundreds of thousands of acre feet of water will get spoiled and have to get thrown out-- once the ash source is removed the problem will take care of itself.
Bah! Those signs are just there for peevish people who don’t like the idea of sweaty hikers swimming in their drinking water! I’m sure critters do worse things than swim in the reservoir.
I agree it’s a little extremist to say there’s a big problem, but I still think there’s a potential for a big problem. The reason they have a six-month supply of fresh water in downstream reservoirs is because they have been releasing more water in recent days as a safeguard in case the water is fouled. Using the filters is an expensive proposition and they don’t want to resort to that unless they are out of options.
The threat to power generation is the bigger economic danger right now - they’ve already spent $600K buying power on the market to replace what was lost when the lines were shut down.
What I meant is that we don’t have any other source of water for those things, pure or not. You can buy drinking water in a pinch, but I at least can’t afford to pour that into my toilet tank, even at 1.6 gpf.
Maybe a crisis like this will encourage more brown water schemes to get the permits that they need.
Roddy
If a lot of ash settles into the water, are the ashes full of soluble chemicals that will dissolve into the water and stay there even after the ash solids are filtered out?
San Francisco is buying electrical power from other sources, such as Pacific Gas & Electric.
I doubt that they will shut off the flow of water from Hetch Hetchy even if it becomes undrinkable. I would expect the San Francisco Public Utilities Commission to tell people not to drink tap water, but still allow it to be used for bathing and other purposes.
Not likely. Turbines used for large-scale hydroelectric power generation are, um, large in scale. A little ash isn’t going to clog anthing at all. Frankly, a LOT of ash won’t, either. Even small chunks of wood won’t be a problem. Whole tree trunks? No problem either because there are grates at the water inlets to keep that kind of stuff out. Afterall, they do get deadfall from time to time, even when there are no fires.