Dam!

November 4, 2011 12:30 PM

On October 26th, a hole was blasted in the base of 125' tall Condit Dam on the White Salmon River in Washington. In less than 2 hours, the reservoir behind the dam drained completely and the White Salmon flowed unimpeded by a dam for the first time in 100 years.

Lots more info and more videos on the guy's Vimeo page and the project homepage.

posted by unSane (72 comments total)

That's a lot of fucking silt.
posted by entropicamericana at 12:35 PM on November 4, 2011 [5 favorites]

I was wondering what the hell happened to the wildlife downstream.
posted by unSane at 12:38 PM on November 4, 2011 [2 favorites]

It seemed more like a dam of silt rather than a dam of water. Amazing footage!
posted by a womble is an active kind of sloth at 12:38 PM on November 4, 2011

I loved the time-lapse part where the lake bottom slumps and erodes in almost real time as the river cuts through it. Very cool.

Is there backstory on why the dam was destroyed and how they convinced anyone to do this? I saw some stuff on the blog, but it isn't every day that people actually fighting for dam removal get their wish.
posted by mathowie at 12:40 PM on November 4, 2011 [1 favorite]

I was wondering what the hell happened to the wildlife downstream.

Local news stories said that essentially, everything downstream was going to be fucked. But it would be much better in the long run. Salmon from below were moved above the dam, so they would "imprint" on the streams above and would know to come back there.
posted by Cool Papa Bell at 12:40 PM on November 4, 2011 [3 favorites]

Is there backstory on why the dam was destroyed

Cost/benefit analysis said destroying it was cheaper than upgrading it.

When the dam came up for re-licensing in 1991 before the Federal Energy Regulatory Commission, it became clear to PacifiCorp that taking the dam out for $33 million would be a lot cheaper than bringing it up to modern environmental standards at three times the cost.
posted by Cool Papa Bell at 12:42 PM on November 4, 2011 [2 favorites]

Um, is there a particular reason why you wouldn't drain the lake through normal means before blowing a hole in the dam?
posted by wierdo at 12:43 PM on November 4, 2011

Really amazing. I love that stuff like this is getting documented - and documented well - and then shared for everyone to see. Imagine if all of human history had such documentation. In addition, this is interesting ecologically and I'll look forward to hearing about the successes and failures and eventual re-habitation that occurs. Thanks for posting!
posted by (Arsenio) Hall and (Warren) Oates at 12:44 PM on November 4, 2011

Yeah, the NatGeo news story says the same thing.

According to Indian Country, Wednesday was "a happy day for tribal members, the salmon, and for the White Salmon River itself." The paper pointed out that fourteen years had passed since PacifiCorp, the Confederated Tribes and Bands of the Yakama Nation and the Columbia River Inter-Tribal Fish Commission (CRITFC) co-sponsored the studies that showed dam removal could be cost-effective.

Efforts by those groups and environmental organizations helped lead to the final moment.

According to news reports, Portland-based PacifiCorp had decided that it was cheaper to source the dam's 14 megawatts elsewhere, rather than install expensive fish ladders and other improvements on the site, as would have been required for relicensing. According to the AP, the dam removal cost around $32 million, while the improvements would have cost $100 million.

posted by unSane at 12:44 PM on November 4, 2011

Um, is there a particular reason why you wouldn't drain the lake through normal means before blowing a hole in the dam?

I just did some napkin math and came up with: AWESOME!?!
posted by odinsdream at 12:45 PM on November 4, 2011 [22 favorites]

When the dam was built, everything downstream was fucked. When it was destroyed, everything that grew to replace it was fucked. It too will be replaced until humans intervene. It's the circle of life.

is there a particular reason why you wouldn't drain the lake through normal means before blowing a hole in the dam?
Keeping the price tag down to $32 million.
posted by oneswellfoop at 12:46 PM on November 4, 2011

Um, is there a particular reason why you wouldn't drain the lake through normal means before blowing a hole in the dam?

What sort of normal means - buckets?
posted by dirtdirt at 12:46 PM on November 4, 2011 [4 favorites]

Um, is there a particular reason why you wouldn't drain the lake through normal means before blowing a hole in the dam?

The more powerful flow will help push a lot of the silt further downstream. If they let the water out slowly, a lot of the silt would remain abouve the dam and/or be deposited right below it. When you silt up the river you raise and widen the channel, making it more conducive to flooding at that point.
posted by oneirodynia at 12:46 PM on November 4, 2011 [9 favorites]

Wow. I'd like to see da Vinci's or Hokusai's depictions of this. It looks like an extrapolation of their vision.
posted by StickyCarpet at 12:47 PM on November 4, 2011

Not gonna lie, I was expecting a lot more salmon in that video.
posted by nathancaswell at 12:50 PM on November 4, 2011 [9 favorites]

> Um, is there a particular reason why you wouldn't drain the lake through normal means before blowing a hole in the dam?

Because they aren't just removing the dam, they are trying to drain the silt bed of the lake that formed behind it.

So violently causing the dam to drain the lake will spread out the silt at one moment, in a controlled (and planned space) vs draining the lake first, then removing the dam, causing a flash flood / silt event in the spring when it is our seasonal flooding time around here.
posted by mrzarquon at 12:50 PM on November 4, 2011 [3 favorites]

$32 million seems like a lot for a few sticks of dynamite. I assume most of that cost was the years of planning and redistribution of salmon and other wildlife? Possibly even relocation of houses or other property? Where is most of that expense going?
posted by (Arsenio) Hall and (Warren) Oates at 12:50 PM on November 4, 2011

According to news reports, Portland-based PacifiCorp had decided that it was cheaper to source the dam's 14 megawatts elsewhere (emphasis mine)

I'm normally not one to be happy about taking out a relatively clean source of generating power for fish. I mean, come on. It's hydroelectic, right?

But I recently read that many of hydroelectric dams are a) generally old and b) weren't generating much power anyway. That a single modern, efficient, well-placed wind turbine can generate what these older dams do.

So ... fire in the hole!
posted by Cool Papa Bell at 12:53 PM on November 4, 2011 [2 favorites]

Um, is there a particular reason why you wouldn't drain the lake through normal means before blowing a hole in the dam?

Most dams don't have a way of completely draining them. Generally a hole at the bottom of a dam screams potential point of catastrophic failure, and any diversion tunnels used during construction are generally filled in or modified into part of the power generating structures.
posted by Badgermann at 12:54 PM on November 4, 2011 [2 favorites]

I'm guessing that the $32million also includes the removal of the structure itself, they are't going to leave the dam there now, but since it is no longer holding up a 125' wall of water, they can remove it pretty easily, all things considered.
posted by mrzarquon at 12:54 PM on November 4, 2011 [1 favorite]

There was a settlement agreement, and revegetation and monitoring were part of that, so I imagine those costs are included. I don't think they are re-dstributing any wildlife- the explosion was planned for this time because it's the least disruptive to existing fish.
posted by oneirodynia at 12:56 PM on November 4, 2011

Didn't somebody say upthread they were moving the salmon upstream above the dam? Seems like that would be (or at least could be) costly.
posted by (Arsenio) Hall and (Warren) Oates at 12:56 PM on November 4, 2011

This makes me happy. Next, Glen Canyon! /abbey fan
posted by zomg at 12:58 PM on November 4, 2011 [7 favorites]

OK, but did they find Chandra Levy?
posted by dhartung at 12:58 PM on November 4, 2011

> I'm normally not one to be happy about taking out a relatively clean source of generating power for fish. I mean, come on. It's hydroelectic, right?

Fish are a huge source of revenue here along the Columbia river, especially for the Tribal groups who have fishing rights.

Not to mention this is just upstream of the Bonneville dam, which produces on average 1100MW. In fact I believe last year the flood waters were so high that in June / July they had to have the wind turbine plants disconnect from the grid and stop power generation, because the Bonneville dam system was running at above operating capacity and they had to get the power onto the grid somehow (flood gates were already fully open, etc). If there is ever an example of what a smart grid system could do, it would be that the excess power we generate here along the columbia could supplement the needs of northern california or even LA, if we had a way to efficiently get the electricity there.
posted by mrzarquon at 12:59 PM on November 4, 2011

I like to think that the fish had, over their 100 generations in confinement, developed religious beliefs about The River Beyond. And that when the dam was broken, the fish who swam through the portal did so with the sense of a prophecy fulfilled.

I only hope they weren't expecting to meet dead loved ones on the other side.
posted by Trurl at 12:59 PM on November 4, 2011 [23 favorites]

mrzarquon wrote: > Um, is there a particular reason why you wouldn't drain the lake through normal means before blowing a hole in the dam?

Because they aren't just removing the dam, they are trying to drain the silt bed of the lake that formed behind it.

So violently causing the dam to drain the lake will spread out the silt at one moment, in a controlled (and planned space) vs draining the lake first, then removing the dam, causing a flash flood / silt event in the spring when it is our seasonal flooding time around here

So let's screw up the areas downstream to save a few bucks? Sounds like a great plan.
posted by wierdo at 1:06 PM on November 4, 2011 [1 favorite]

Really, a tangential shot at religion in this thread? Come on.
posted by oddman at 1:08 PM on November 4, 2011

the explosion was planned for this time because it's the least disruptive to existing fish.

I assumed that if you throw explosives in the water, all the fish bubble up the surface, dead.

It's a fishing method.
posted by alex_skazat at 1:11 PM on November 4, 2011

Um, is there a particular reason why you wouldn't drain the lake through normal means before blowing a hole in the dam?

What fun would that have been?

and the bed of silt transport of course.
posted by longsleeves at 1:11 PM on November 4, 2011

wierdo: they're fixing the areas downstream by restoring the natural flow of the river. It's not like it's going to flood a city downstream.
posted by thylacine at 1:11 PM on November 4, 2011 [2 favorites]

So let's screw up the areas downstream to save a few bucks? Sounds like a great plan.

The areas downstream were going to be screwed one way or the other. By doing it this way, they reduce the potential for repeated flooding down the road.
posted by valkyryn at 1:12 PM on November 4, 2011 [2 favorites]

Maybe Ulysses Everett McGill can find that wedding ring now at the bottom of that durn big lake.
posted by yeti at 1:14 PM on November 4, 2011 [5 favorites]

valkyryn wrote: The areas downstream were going to be screwed one way or the other. By doing it this way, they reduce the potential for repeated flooding down the road.

Explain it to me more slowly. Seems to me that draining it as much as possible using whatever mechanism the dam has for doing so, and only then dynamiting would have reduced the amount of silt transported downstream. Then there are these big yellow machines that can remove most of the excess silt that still remains.

I'm not really seeing how silting up 10 or 20 miles of river is inevitable here.
posted by wierdo at 1:15 PM on November 4, 2011

The salmon must flow!
posted by zippy at 1:15 PM on November 4, 2011 [1 favorite]

Um, is there a particular reason why you wouldn't drain the lake through normal means before blowing a hole in the dam?

Besides the silt reasons, the other issue is that the river is in a fairly rugged area. Here's the Google Terrain map. The area is quite close to the Columbia River Gorge, and the White Salmon River is in a canyon of its own. To anyone thinking this is saving "a few dollars" consider trying to re-route water through a 200' cliff on one side and a 1000' cliff on the other: there's nowhere else to run the water without a huge amount of damage to the rest of the area.

If there is ever an example of what a smart grid system could do, it would be that the excess power we generate here along the columbia could supplement the needs of northern california or even LA, if we had a way to efficiently get the electricity there.

The Pacific DC Intertie already exists to blast 3100MW down to LA, and it still wasn't enough to offload the power that the wind/hydro were churning out this year.
posted by Mister Fabulous at 1:15 PM on November 4, 2011 [4 favorites]

It's shockingly expensive to cut up and haul away a large structure like a dam and my guess is that's the majority of the funds. Lots and lots of equipment time, man hours, dump trucks and fuel. I've been involved in many small dam removals, but not this one.

As far as damaging existing habitat, either its consistent with the natural flow regime in which case it'll regenerate in its own very, very quickly. Or its not and it won't come back. Either way its a blip in time for the river.

Blowing out the dam and letting the sediment go us the easiest way to fix the sediment starved reaches downstream and to establish a new channel through the lake bed. No point in dragging it out or moving all the mud with excavators when you have a perfectly good river to do it for you. As long as the sediment isn't contaminated and there's nothing downstream to destroy or flood, this is SOP.
posted by fshgrl at 1:21 PM on November 4, 2011 [8 favorites]

Seems to me that draining it as much as possible using whatever mechanism the dam has for doing so, and only then dynamiting would have reduced the amount of silt transported downstream. Then there are these big yellow machines that can remove most of the excess silt that still remains.

Silt is not just bad stuff that needs to be eliminated.
posted by rhizome at 1:23 PM on November 4, 2011 [2 favorites]

I'm not really seeing how silting up 10 or 20 miles of river is inevitable here.

It's only two miles from the dam to the mouth of the river into the Columbia. There's a lot of water moving through the Columbia, several times that of the White Salmon.
posted by Mister Fabulous at 1:23 PM on November 4, 2011 [1 favorite]

dhartung: OK, but did they find Chandra Levy?

No, but they did find this weird corpse of a skydiver whose parachute didn't open, with $200,000 in $20 bills strapped to him.
posted by AzraelBrown at 1:24 PM on November 4, 2011 [13 favorites]

I'm normally not one to be happy about taking out a relatively clean source of generating power for fish. I mean, come on. It's hydroelectic, right?

Hydroelectric power is generally only considered clean to people who don't live lives dependent on riverine ecosystems.
posted by docgonzo at 1:25 PM on November 4, 2011 [6 favorites]

The Pacific DC Intertie already exists to blast 3100MW down to LA, and it still wasn't enough to offload the power that the wind/hydro were churning out this year.

Transmission is a real problem, especially when you are dealing with generation that varies a lot over the year. The price of power is sometimes negative during high water season nights in this area.
posted by ssg at 1:27 PM on November 4, 2011

Armchair hydrologists - who knew?
posted by odinsdream at 1:29 PM on November 4, 2011 [9 favorites]

it's well known that fluvial systems is a big hobby/interest for mefites.
posted by rainperimeter at 1:32 PM on November 4, 2011 [2 favorites]

Thanks for the explanations of the science and economics behind this video. I'm an environmentalist that sees dams as a net positive, with reservations, so this was educational. Metafilter ftw.
posted by RolandOfEld at 1:33 PM on November 4, 2011

it isn't every day that people actually fighting for dam removal get their wish.

There are a number of dam removals going on in Washington. The first were a set of abandoned dams on Icicle Creek. The next ones up are a pair of dams on the Elwha river, out on the Olympic Peninsula (and actually inside the Olympic National Park!). No, it's not every day, but it does seem like the idea of dam removal is becoming more acceptable.

The one I most want to see destroyed is O'Shaughnessy Dam, inside Yosemite - its construction flooded Hetch Hetchy, an alpine glacial valley whose beauty once rivaled Yosemite Valley itself. The mountain walls of the valley are still beautiful - I hiked there many times as a kid - but the lake that occupies the valley floor is as ugly and barren as any reservoir.
posted by Mars Saxman at 1:36 PM on November 4, 2011 [1 favorite]

The utility's site has a lot more info too.
posted by smackfu at 1:37 PM on November 4, 2011

Then there are these big yellow machines that can remove most of the excess silt that still remains.

I'm not really seeing how silting up 10 or 20 miles of river is inevitable here.

Rivers move silt all the time. It's what they do, and why we have fertile alluvial plains and storm buffering wetlands and all those useful things. Transporting silt (to where, exactly?) is hugely expensive and totally not worth the several years it would take to do it, when the river can do it much more efficiently, effectively, and usefully by itself.

Hydrologists used to think they could engineer stream flow, by digging a little deeper here, laying down some gravel there, &c. Extensive computer modeling has failed to support the idea that we really know what we're doing as far as river dynamics- quite the opposite, and it's been proved to be very costly. The least resource intensive and ultimately the least destructive over the long run is to let the river do the work, because it is going to anyway.

This has been years in the making, and I'm not sure why you think that if the silt was a problem downstream, it would have been casually dismissed. It's going to cause some environmental destruction, that's known. But the benefits far outweigh the short term (we are talking about geologic time) problems.
posted by oneirodynia at 1:44 PM on November 4, 2011 [5 favorites]

Yeah, the restored flow of the river will disperse the silt downstream, as it would have been in the natural pre-dam river. Going to take a while. People apparently don't realize that dams have a lifetime - they fill up with sediment and become useless. This one looked like it was almost totally full of silt.
posted by zomg at 2:02 PM on November 4, 2011 [3 favorites]

When the dam was built, everything downstream was fucked. When it was destroyed, everything that grew to replace it was fucked. It too will be replaced until humans intervene. It's the circle of life.

Sounds more like the circle of fucked, but I don't think you're totally full of silt.
posted by Kirth Gerson at 2:15 PM on November 4, 2011 [1 favorite]

This is a "large dam" (defined as over 45 feet tall). The world has 48,000 large dams, with an additional 1,600 currently under construction. I'm not sure how many are under de-construction but probably just a handful. China has the most, followed by Iran, Turkey, Japan.
posted by stbalbach at 2:20 PM on November 4, 2011

Wow, you can see the old logs they used 100 years ago as part of the river diversion now that the reservoir is empty. Neat.

And you can see how much sediment and silt has been starved from the downstream ecosystem (silt isn't necessarily bad). Flush it out, let it start over.

I'm just guessing, but I'd assume a significant part of the $100 million quoted as the "upgrade / rehab" the dam included removing all that silt. So would you rather this project cost three times as much and take three times as long, to shorten the ecosystem rebuild time from one year to six months? Within a year or two, the river system should be pretty much back to pre dam levels of health.
posted by mrzarquon at 2:21 PM on November 4, 2011 [1 favorite]

Alright - who let Derrick Jensen out again?
posted by symbioid at 2:31 PM on November 4, 2011 [1 favorite]

Think of it as like controlled burning in forests. We overprotect some forested regions because they are close to human concerns, this ends up eventually creating a more dangerous environment with tonnes of unburnt fuel, brush and natural fallen trees and other such stuff. So, the NFS regularly goes in and intentional set fires to areas with excess fuel. Yeah, the fire fucks with the established ecosystem, but the wider ecosystem is not a static thing, it actually requires fire at regular intervals, there are trees and plants that need the heat provided by fire to sprout their seeds. And so, fire as it turns out is a good thing for forests, in the long run. Floods too are a natural process and are beneficial to the wider ecosystems, while being pretty damaging to the system as-is. But we fear and struggle with floods (and fires) because they don't play nice with human concerns.

The dam destruction is causing havoc downstream for now, but it is a havoc that was born about by a past havoc. The reservoir certainly damaged a lot of the system that was in place, the loss of water downstream was damaging to the dynamic system.

I can see the need for some dams.. but I will always cheer the well orchestrated destruction of them.
posted by edgeways at 2:33 PM on November 4, 2011 [2 favorites]

Alright - who let Derrick Jensen Hayduke out again?
posted by alex_skazat at 2:33 PM on November 4, 2011 [2 favorites]

One should also note: WA is also removing other dams, these located in the Olympic Peninsula, next year, the Elwha Dam and the Glines Canyon Dams. These will be removed over the next three years to restore the river to free-flowing status. This project is being done by the National Park Service. (Page includes links to webcams to watch the deconstruction, etc.)
posted by hippybear at 2:49 PM on November 4, 2011

About the O'Shaughnessy Dam -- one thing that has been said in its favour is that since it impounds water for the Greatest City On Earth (San Francisco), the surrounding area has remained protected from humans, as a wilderness area. After all if you look at Yosemite Valley today, there's nothing natural about it.

And that dam too will fail or be removed -- although maybe not in my lifetime.
posted by phliar at 2:50 PM on November 4, 2011

Hayduke Lives!
posted by zomg at 3:06 PM on November 4, 2011 [1 favorite]

The Marmot Dam was removed from the Sandy River in Oregon in 2007 by building a sediment backup dam while removing the existing structure. video. At the time it was the largest concrete dam ever removed in the U.S. It was estimated to take 3–6 mos to drain the sediment, but it took less than a month for the river to return to its original flow and color. The Sandy River has its headwaters at Mt. Hood and joins the Columbia River 14 miles east of Portland.

Last year a coffer dam at Gold Ray Dam on the Rogue River in Oregon broke earlier than scheduled video.
posted by asfuller at 3:07 PM on November 4, 2011

That's really cool. But is there a video from a different angle so I can get a better look at the water horse spirits that Arwen summoned to drown the Nazgul?
posted by dry white toast at 3:18 PM on November 4, 2011

"Let my people flow..."

There are few demonstrations of human unbuilding that are so pleasing to watch. At long last, the barrier has been removed and the system begins healing. It is akin to watching an innocent man be released from prison.

One does not realise how malformed the landscape has become until it returns to its natural state -- in an instant. The continued proliferation of humanity will always have an impact on the natural environment and its pleasing to see that we are now learning to manage and undo our impact.

This is not the kind of thing that will be trumpeted on the front page of the global media or even attract nary a glimpse from more than a small population of people interested in This Kind Of Thing. However, this is tremendous triumph of the human-nature partnership.

One can only hope in time -- when we have evolved greater solar generation resources -- we will undo the greatest indulgences.

Ode to Mexican farmers and urban planners when the monolith finally recedes and equity is re-established.

Joyous shouts from fertile mother Africa, when she again lives unconstrained by economic machinations.

Dam building will one day seen as one of the most primitive modalities of human society -- literally a form of passive and silent warfare on environmental sustainability and the people downstream.

We should not feel guilt, for we did not know that what seemed like achievement was, in fact, enslavement; creation was actually destruction, of ourselves and of an environment without a voice or vote.

Yet when you see the glory of the water flowing, instantly returning to its course, its banks instantly nourished, one cannot help but feel pride and hope for those humble souls slowly cleaning up the detritus of previous ignorance.

Damn.
posted by nickrussell at 3:25 PM on November 4, 2011

Also, looking at this video, I realized I would not want to be the guy whose job it is to dig out part, but not all, of the base of the dam to lay the charges for the explosion. You really got to hope that the 100 year old schematics and design of the dam are accurate.
posted by mrzarquon at 3:29 PM on November 4, 2011

The absolute best part of that video was the lack of music. I'm grateful to the videographer for just letting us watch and listen.
posted by komara at 3:40 PM on November 4, 2011 [4 favorites]

Dam porn/snuff videos, exciting stuff.
posted by nostrada at 4:00 PM on November 4, 2011

Dam building will one day seen as one of the most primitive modalities of human society -- literally a form of passive and silent warfare on environmental sustainability and the people downstream.

I'm no fan of all the hydropower dams on the rivers here -- it's only cheap power if you don't count any of the environmental costs. But without dams, you don't have irrigation. Without irrigation, you don't have people on any scale larger than hunter/gather groups, pretty much. All those cool ancient civilizations relied on amazing irrigation projects, including dams, diversions, impoundments, and canals. All those things are absolutely necessary to grow food in most areas, but have tremendous environmental consequences.

And in places where you don't have to irrigate, like in northern Europe, people have spent thousands of years learning how to remove water from land, by digging ditches, tiling fields, pumping, etc, which is equally unnatural and high impact. So while I'm all for tearing out these huge, ugly, nasty dams, there's some level of dam activity that's going to continue for as long as we want to have lots of people and enjoy the things we call "civilization."

These dam removal videos make me incredibly happy to watch, though. I've grown up in a pacific northwest totally shaped by dams, large and small. Every one that is removed is a step in the right direction.
posted by Forktine at 4:26 PM on November 4, 2011 [1 favorite]

I am very keen to see how the rivers and their fish populations recover above and below these recently removed dams in the Pacific Northwest. Here in Alberta we have 2 small but very destructive hydroelectric projects, at Spray Lakes and Lake Minnewanka. The dams involved, and their reservoirs, have destroyed unique fish populations supposedly protected in Banff National Park. Suggestions for removing one of the dams in the 1990s during relicensing deliberations were considered wildly unrealistic because Parks Canada couldn't imagine how the rivers and their fishes could be restored. Now we will find out.
posted by dmayhood at 6:41 PM on November 4, 2011

I'm an environmentalist that sees dams as a net positive, with reservations, so this was educational.

It's all about the specifics. In environmental policy, in energy, in transportation - understanding the specific case you're dealing with is essential to doing the right thing. That's (part of) what makes crafting national policy so hard. It's very very hard to come up with the kind of general rules that a country the size of the US needs without simultaneously creating situations that are totally fucked up. It may be impossible, but I'm an optimist.
posted by nickmark at 9:38 PM on November 4, 2011

The dam created an ecosystem of its own. I spent many hours at Northwestern Lake watching beaver, all manner of waterfowl, waders, raptors, frogs, snakes, turtles, etc. etc. Generations of local people who fished, paddled, picnicked, swam and enjoyed the peace are saddened by the lake's disappearance. Despite saying that, I am glad the river is a river again. But it is like losing an old friend.
posted by wiinga at 11:32 PM on November 5, 2011

I spent many hours at Northwestern Lake watching beaver

If there are beaver around, there may be another dam and another lake one of these days. They tend to do that.
posted by hippybear at 6:48 AM on November 6, 2011

Since so many people commented on the wisdom of blowing a hole in the dam at the bottom rather than starting from the top, I note that the latter method is apparently being used at the Gline Canyon dam mentioned upthread; time-lapse video here, current progress here. I don't know enough to judge the merits of either approach, but apparently both are used from time to time. Being the guy on that barge would make me pretty nervous, though.
posted by TedW at 8:52 AM on November 7, 2011

Context: Condit Dam and Northwestern Lake, on Google Maps. You can compare what it is and what it is going to become on here.
posted by filthy light thief at 12:42 PM on November 9, 2011

And if you pan south, you'll see the size of the lake vs. the Columbia River. Zoom out, and the lake disappears, but the Columbia is still visible.
posted by filthy light thief at 12:44 PM on November 9, 2011