drop by drop the Sandy River erupts on the slopes of Mount Hood bound for the Pacific Ocean pouring itself through the Cascade Range and into the Columbia River 50 miles away it's a liquid highway for salmon the thought is that they migrate by a sense of smell it's probably more than that it would be absolutely impossible for a human being to navigate without instrumentation 2,000 miles out in the ocean and then find their way back you know into this river so they're biologically programmed to survive in circumstances that we probably don't even understand for almost a hundred years Portland General Electric PGE has harnessed the river at Marmot van twentieth century technologies like this fish ladder help salmon over the 50 foot phase but new requirements to protect endangered species mean that modernizing the system of fish protections is prohibitively expensive our customers expect us to do the right thing and if a project cannot be run economically and protect the salmon they expect us to remove the project so PGE is planning the largest dam removal in Oregon history it's no simple task there's a lot of things that we don't know that we'll learn as we actually see it take place there could be some bumps in the road on their way to the for the Promised Land the project's biggest unknown lies in the reservoir behind Marmot over the decades a million cubic yards of sand gravel and boulders enough to fill a hundred thousand dump trucks eroded from Mount Hood and became trapped against the dams concrete wall today the deposits taper upstream for more than a mile burying the Sandy's former channel beneath it the reservoir behind the dam is effectively : so that sediment is actually stacked just about to the lip of the dam with the dam gone the debris would become a five story roadblock to fish it too must be taken out but how and most of the dam removals that have occurred to date you get down here with a backhoe and a dump truck and you cart the sediment away prior to the removal that's a problem in a river that supports endangered species of salmon the more sediment you remove behind the dam the more time you're in the river the more time you're in the river the longer the effect is on this aquatic community downstream to protect salmon habitat work in the river is limited to a four-month period during low flows we basically have to do this job in about half the time that that normally would take in under normal conditions it'll take six and seven days a week and some long hours to get finished and meet the October deadline that's not enough time to make 36 billion pounds of sand and gravel disappear with backhoes so PGE has come up with an unconventional plan focus the energy of a fall rain storm against the sediment and let the river cart it away before salmon return to spawn it's got to be clear enough that we have fish passage again the catch no one's ever tried this on a grand scale there's never been a human constructed dam coming off a river that has involved this much release sediment have never seen what happens when a million cubic yards of sediment comes down a river all at once most people think about dams in their role as holding back water but barmouth dam doesn't really do that it diverts water where it's used for for hydroelectric production Marmot was built to send flows into a canal that tunnels through a mountain The Devil's Backbone and joins water diverted from the little sandy river into a three mile wooden flume ending at Rosalind Lake 160 acres of potential energy from here it tumbles into the bull run powerhouse with enough force to make electricity for up to 16,000 homes I'm quite impressed by the engineers of a hundred years ago I mean these guys didn't have any of the modern tools they didn't have electronic surveying instruments they didn't have aerial photos and yet they managed somehow to engineer these very efficient systems for capturing water diverting it and using it to generate hydroelectric power which was the marvel of the age workers began construction on Marmot in the summer of 1912 wilderness was their hardware store stocked with stones and Timbers so much of the stuff was done with by hand and horsepower very little mechanical stuff except some steam equipment they finished seven months later in February of 1913 it's a legacy project to us it was one of our first hydro projects the original dam endured the rivers pounding for three-quarters of a century until 1989 when contractor NAT mcdougal replaced the weakening structure with concrete and rebar now he's back to bring it down this dam was built to last not to be torn out 20 years after it was built this is very hard for me personally to take this thing out and it's going to be an experience for us that's not easy to do his first challenge is to isolate Marmot from the river so deconstruction can begin crews lay a roadside strip of sand and gravel across the reservoir inside it they install wells and pumps through 50 feet of sediment to the riverbed the result is a cofferdam an ingenious piece of engineering that turns wet earth into a dry barrier as long as the pumps stay on we're working behind a temporary dam if any kind of failure we're doing current would be a trully major catastrophe trying to pump the water out and control that water that is the biggest single risk we have months from now if the coffer dam functions as planned it could also play a starring role in solving the sediment problem until then there are a few details to settle that's why PGE has asked gordon grant to lead a team of scientists on an unusual mission so we're standing out here on the glorious summer day in Oregon but halfway across the country in the bowels of a dark laboratory right along the banks of the Mississippi River they're building a model of this river on the campus of the University of Minnesota at the National Center for Earth surface dynamics researchers prepare a scale model of the Sandy where it meets Marmot Dam on the face of it the model is a very simple system you've got a topography you feed it water you feed it a mixture of fine sand and gravel and gravity doesn't magic and that's it but what is fascinating about it is that the model with those simple elements comes to life all right well let's take the dam out as in the real world once Marmot is removed the coffer dam becomes the center of attention a fall storm hits in the field managers must decide if it's the right size to wash out the sediment I see water coming it's starting to ring the river rises against the copper down it's like a horse clawing at the stall door that horse is gonna run workers remove the pumps that keep it dry and stable get ready they notch it to focus the river's energy and they seal off the canal to boost flows here we go water charges out of its only exit oh you're looking look at look at look at there underneath underneath that look underneath underneath underneath there goes Wow look at that thing go whoo as the coffer dam collapses the sandy rips through sand and gravel in the reservoir opening a channel for fish over the next month Gordon and his team will run many more scenarios as they seek out the ideal conditions for carving away the most sediment in the meantime there's a dam to take down this all started a long time ago there there's a lot of engineering involved to design where the holes are going to be how many holes how much explosive weight is going to go in each hole demolition expert spec into the top quarter of Marmot preparing the first of four blasts to fracture its concrete there's a very heavy rebar mat on one foot centers both directions horizontal and vertical so it's a real challenge to get a hole in the right spot at the base of the dam biologists have their own slippery challenge now that the rivers diverted around Marmot the fish ladder is out of service Sam are stranded some of them are very large we had some fish that were low over 40 pounds they've raced thousands of miles back from the ocean to spawn and the gravels of their birth before they died with just miles to go these creatures risk burning out the last of their energy we call it a fish rodeo because it is you have a lot of people you have a lot of fish they're zipping all over the place you're chasing them around with a net they catch them and it's always a challenge to get them out you don't hurt them and you've got to get them back in the water as fast as you can Wrangler speed the salmon - habitat above Marmot just in time the demo team is rigging up four tons of explosives once you get it all loaded then you've got people out there hooking them in you've got people going behind the people hooking a man to check to make sure they were hooked and right a community of political leaders conservationists and reporters arrives to commemorate the dams last stand put the shot show primer in the mushroom starter when you hit the primer it will ignite the lead-in line and the lead-in line goes out and ignites the shot but isn't gentlemen we're about one this shot has been checked at least four times by four different people to make sure that there was no mistakes made that it was gonna go exactly the way it was designed are we ready in this business you can't not help but be superstitious Portland General Electric CEO Peggy Fowler is about to make history on a project like this it's a big day when the first shot goes off because it means not only can we really start doing what we're here for but we'll be able to see just how difficult it's going to be to break this stuff and dig it and get it out of here Marmot is a stout 25 thousand ton fortress laced with 200,000 pounds of steel rebar and just now more than a few cracks crews and heavy equipment take it on like ants at a picnic it's just like having your hand out there I mean here you're in total control yo you can pick up a piece of one-inch rebar with between the teeth and the thumb and sort it out thank you probably picked the hair off the top of your head with it if you had any the debris is destined for reuse a crusher turns concrete to Road fill metal scrap lands in an electric arc furnace 70 million watts of energy make it new again and day by day the dam grow smaller shot prepared to fire in five seconds Larry are you clear all clear it's on the way so take about two more weeks to get rid of this and the rebar remove the rest of the material on the backside of the dam at that point we pretty much clear the site wait for the rains to come in in the fall the rains come in in the fall they wash out the cofferdam what happens then as a material migrates downstream is something we're all waiting to see in just three months Marmot disappears what's left behind is a mountain of sediment and a cofferdam holding back a river quiet before the storm there's nothing predicted in a long-range forecast so we could be as late as you know October 15th waiting on a storm the perfect storm on a day like today we can easily wait across the river and then barely get wet but if we come out here in a couple of weeks the flows will just be booming through here so don't be fooled by the biblically Brooke it's it's really a very powerful River the Sandy is also a flashy River when rains move through water levels rise and fall quickly increasing the tension around a high-stakes decision the choice of storm is going to be a one-time shot we're not going to have a second chance when we choose a storm right wrong or indifferent we're going to breach the coffer dam the choice may be at hand the National Weather Service in Portland is tracking an early storm season normally in the Pacific Northwest we get some nice weather in the fall this year and we just went from summer to winter PGE has asked forecasters for help but that's no simple matter sometimes around here it's it's difficult to figure out whether or not it's going to rain it's a it's a challenge just to get a handle on the storm systems that are coming in you break that down to the Sandy just a small area a couple hundred square miles and you know is it going to rain in that little River Basin if so how much is it enough to really cause significant rise on the river that's that's a tough question for us to view a storm that's too big we'll swap the chance to guide as much sediment as possible through a notch in the copper dam it's been designed to handle a certain amount of flow above that it's going to wash out regardless of what we do if the storm is too small the sediment will stall slowly bleeding into the river hopefully we can maintain the coffer dam until it's an event that's big enough to really move this material after years of hard work opening a channel for endangered fish depends on a little help from Mother Nature we know the sediment will move out we know it will move out at a rate that's been determined by what the flows are going to be and the duration of the flows with no ability to predict those we really don't know it's going to prepare for the unexpected biologists activate plans to protect the Sandy's most endangered fish 18 miles below the cofferdam hold on to a sec full tide a little bit well we got one today we're here collecting 20 pair of fall chinook salmon as an emergency program basically in case the worst-case scenario happens since we're in essentially a race before the dam gets breached if sediment jams the river the eggs of spawning fish could suffocate and die here so biologists deliver breeding pairs to the sandy hatchery as a precaution well spawn those fish at the hatchery raise the juveniles until spring and then release them back into the river so they'll naturally out migrate to the ocean the back-up plan is timely overnight rains have filled the reservoir behind the cofferdam this morning on my way out I got a call just before I turned into the access road and I was told the river of that nineteen hundred CFS so I drove a little faster on the access road get in here a surprising 850,000 gallons of water a minute is now pulsing down the sandy it was not what it was supposed to be when I looked this morning around 4:00 a.m. it was goes to a thousand CFS I thought okay the rain is letting up looks like we're okay at 1900 CFS is the design for the cofferdam on what it's designed to hold back any higher than that it's anybody's guess the river has pushed the cofferdam to its limit and created an urgent problem are you comfortable still having equipment come across here now the bridge washed out on that back corner there and it sunk probably a foot the bridge over the diversion canal was failing and the project confronts its most serious crisis we've now isolated the cofferdam with no way to get equipment back out there to deal with the pumps the casings you know it's that's just that's unacceptable the rains paws opening a window of valuable time to mobilize crews we call now to the forecast see if there's thinking that this stalling that flows is going to last long enough National Weather Service Portland hi Andy Tim Keller here I got John Dessler - hi Andy well do we have a forecast yet the forecast Center is tracking another storm the models are more and more pointing towards development along this part of the frontal band and that's going to be the player for tonight so Tim looking at the hydrograph this looks like the one that's going to do it crap is 2505 boy and then actually going higher we're not gonna hold off the breach it's gonna go to 2500 at it we had to keep going we gotta get going alright Andy see ya hey thank you let's do it okay because the bridge can no longer support heavy machinery notching the copper dam has become more complex looking at the bridge with the water coming up as fast as it is it's hard to tell you know if the forklifts gonna do it we need it to do hopefully it'll all go good nobody will get hurt out here the first step is to remove the pumps carefully but quickly once we get out there and pull the first pump on there we in a sense of live diffuse and integrity of that section of the cofferdam is weakening as we speak at that point you can't count on that cofferdam as the project enters its final hours gordon grant is eager to see how the river performs removing the stand up to now has been all about big machines and big dirt people coming in digging the old dam out exploding it up transforming the space through Machinery but starting this afternoon we move to a whole new rhythm and a whole new cycle where it's the river that will do the work River will cut down the river will move the sediment and what we're left with will be up to the river and out up to the machine with the pumps out of the way art begins the delicate task of cutting a notch it would have been neat to watch it from a distance I think on top of it it's it's nerve-wracking what if the thing does wash out under you know that's the biggest problem I was having is what happens then there are some big big doings happening underneath that thing look at that bad it's very cool hey Dave got a copy I got hey Dave we need to get going we need the rocks in the canal now right Ted for workers o'clock the diversion canal kicking up flows by another two hundred thousand gallons a minute this is just going to explode on you can hear it Wow whoa this is the geological knife right here holy smokes watch yourself here gentlemen job the crew scrambles as we're backing up all the sudden the dam just lets go in a spot probably 10 15 feet across just washed out front yet that's definitely the most nerve-wracking time of it I can feel the ground moving I have never liked that by nightfall the Sandy has cut itself free people have worked many many months and years on trying to figure out exactly how this would happen and to finally see it come to pass I think it just gives everybody a great sense of satisfaction next morning Gordon's back the whole thing River took it all one night like the river doesn't even remember that there was a dam eighteen hours have ticked away since the notch was cut and the river has digested a hundred and ten thousand tons of sediment some of it locked in place for nearly a century yeah there's a hint of sulfur in the air and I think it's coming from all the organics that have been buried under this reservoir for I don't know 80 80 90 years but the reservoirs gone the dam is no more this is a river transformed the site is is very quickly returning to to a natural state two days after the dam went out as I was standing upstream of here I saw a pair of coho to me a small indication of how quickly this system is recovering as part of the restoration 1,500 acres of PGE project lands will become the keystone for a new special recreation area of national significance a wild river refuge we borrowed light our houses to run our computers yesterday but gently down the stream Mary Mary Mary Mary you
