Ok, men. I was informed today that a dam in my area needs to be decommissioned, and I'm the guy they want to do it. The state is working on a plan for what they want done because there is some cost-sharing involved. We know for sure all the concrete, including wingwalls, has to come out. They aren't sure yet what to do with it. We are going to breach the dam somewhere and drain water off. We are estimating there is about 800-1000 acre-feet of water to let off, it's about 6' deep at the dam. The spillway itself is about 8' high, no idea how thick the concrete is. My question for all of you is where would you start, what machinery, etc. Hopefully I can answer questions as they come. And, GO.
I would go with two excavators one with a hammer and one to clean up. Think the thickness would determine what size hoe/ hammer or how fast you want it done. I remember one job we hammered 100 year old concrete that was a water basin for a water authority. That stuff was thick and full of rebar. Took a lot longer with the tired 150 kobelco we were using
Have you considered drilling & blasting to break the concrete, AFTER the water is drained. I can give you guidance in means and methods.
double post
I would bet that it's keyed into rock underneath it since it was poured by the Farm Service Agency or predecessors. I'd think that'd be 10' or so under the dam? How many of those endangered salamanders are you going to run into on the job LOL, or maybe you guys don't have those idiots working up there in the NRCS.
Might have to go pretty deep to keyway into solid rock in many areas of North Dakota. Seems to be lots of boulder strewn base soil when we build the power plants in the 70s. Of course I don't know where the dam is. The spillways we put in were anchored in the rocky soil and then clay lined up the concrete about 6 ft on the water side. In North Dakota that would be the Green Sturgeon. They thought they were extinct, then they found a couple in 1979 or 80.
I'd say a couple of bigger excavator with a hammer and maybe your 210 to help pull the loose concrete out of the way to get it to drain, as for removing the whole thing... blasting does sound fun
Shimmy, I demoed a bigger one than that a few years ago. The first thing I would do is make da** sure I had the water upstream under control. Even in case of an extreme rain event. Make double sure you have an emergency spillway off to the side of your work area constructed before you start. On this one the concrete was 5 feet thick like 390erie stated, full of rebar. It could have passed for a bank vault with all the rebar. We used explosives to loosen it up, a large hammer and two cutting torch crews. Good luck to you.
go to YouTube there are videos of some dams they removed here in Oregon and Washington,they used 2 big track hoes 1 with hammer and 1 with hydraulic thumb and 1 off road 6 wheel dump truck to haul rubble away to recycle pile
This sounds very plausible. Our initial guesses are about 6' of water against the spillway. How far you think they may have keyed it down?
Think my 210 might not be enough of a hammer for the job? I was planning on using my hoe on the hammer, another hoe or track loader for shoving debris out? Here's the next thing. My initial guess was about 40 hours with the hammer to break it up. It was just a rough guess, hopefully I'm not crazy?
Water hopefully won't be an issue as long as I can breach the earth part to create a path for water, AFTER I open the spillway to drain off the main water. I was afraid of the rebar issue as well. The spillway is about 70' long. If I have myself on a hammer, and another hoe pulling debris, are 2 guys on torches going to be enough?
Haven't really though of anything yet besides the obvious hammer it into little pieces. I have zero experience or equipment for blasting, nor do I know anybody that does that sort of thing. Not saying that it's not a good idea though. Would the reduction in work to break it up with the hammer offset the cost of blasting?
When you make the cut to breach the earthen bank, think about taking some of the weir boulders that are presently downstream from the damn and rip rap your breach. (Just in case). The reason being so cautious is the job I did the architect that design the upstream water control system underestimated the flows in a heavy rain event and the whole deal got flooded. The poor fellow committed suicide on account of it. You may even be able to leave the boulders in place, and just cover them back up when finished. That way there will always be an emergency spillway in the future. Keep us posted on your progress, It will be interesting.
I was thinking a larger machine just because then you could run a larger hammer and probably get more bang for your buck, and you would be beating up someone else's machine. I don't really know how long it would take, I haven't ever broken anything quite this thick
Drilling and Blasting concrete is really very simple. Drilling on a 3.0' x 3.0' pattern 9.0' deep using 2" holes, measure the dam long by wide and divide that sum by 3 x 3 pattern (9), that will give you the number of holes you need. SAY: 65 x 5 = 325 sf. / 9 = 36 holes x 9 = 324 lf. The powder factor is 0.10 lbs per cy. of concrete. The dam looks to be 65.0 long x 5.0' wide x 8.0' high say: 100 CY ? = 10 LBS of 40 gel = 10 /36 = 0.30 LB/Hole plus one cap per hole. Remember, you want to break/crack the concrete, not throw it into the next county. The shock of the explosion will also break the bond of the rebar, but those dams are usually not heavily reinforced. When blasting rock, with breaking strength/yield of 40 t0 60,000 psi, the powder factor is +/- 1.0 lb per cy. that concrete is MAYBEY, 3 to 5,000 psi. so when the powder detonates at 13,000 to 16,000 feet per second it is very destructive to the chemical bond of concrete. The drilling can be done by hand with sinker drills or with a air track or hydraulic drill. The blasting can be done by the powder supplier, they usally have blasters on their payroll. Call Austin Powder http://austinpowder.com/ they can advise you and make it a safe, successful job.
I like the old fashion wrecking balls, about 4000 lbs. Once water is out of the way I would start near middle were it is weaker, pound down in lines making rectangles as big as you can handle to put in truck or whatever. A lot of times dropping ball in a line only the steel will break there with no torches. One mistake in my opinion using a ball, operators like to go up and down with boom lever only. If you extend out and use the stick more than the boom dropping the ball it is a lot smoother.:my2c
I would expect about 2/3 the tow in soil as the depth of water its holding on a straight dam. It may get a fair amount thicker at the bottom on the water side also. When they curve the dam they get by with less tow. May be old plans still on file at the governing agency from when it was built. Or even old newspaper articles about it if you know when it was built. You can expect lots of rebar as someone else stated.
you might look into a concrete shear/crusher for a hoe to break up the chunks and release the rebar and save the torch crew
I'd get a quote to drill and blast. It will instantly size and separate your material. When your drilling you'll instantly know how deep the material is also. Compare to your estimated hammer time. Rent the biggest hammer and machine you can find, save yours.
I agree with everyone above, 2 excavators, one with hammer other for clean up into a 6wd articulated truck to recycle pile. However water control and release is another issue, especially if you dont know the thickness of the wall. The way i would do it is use a small trenching bucket to run a drain out and down into the lower section, then do a survey of the wall and judge what machine (especially running the hammer) is needed. Just my 2c excluding GST
There is a significant difference in hammers. Check the foot lbs a hammer for your 200 size machine has vs the foot lbs a hammer for a 30 ton size machine. Then again, if you are running a rental hammer, those tend to have been abused. Just looking at the size of the structure, assuming there is a good bit of bar in there, you are going to need 20-30% more time than your estimate of 40 hours. The bar can be a big plus for you though. Hammering on rebar tends to spread the shock load out and will help pulverize your concrete. As far as a shear or processor, those will only work if you can get the jaws open wide enough to get on the concrete, and looking at that structure, the likelihood of that is slim to none.
Shimmy, iI sent you a PM with info on a blaster we used on a hospital rock job a couple months ago. Not sure if he travels as far as you are but should be able to give you a decent cost estimate.
Being in the NEPA and environmental permit game, here is something that I would look at before dewatering. Consider where and how the water is going. Make sure you don't stir up some greenies because you muddied the water where someone's favorite frog or fish lives. You don't want EPA, USACE, or the state agencies pounding on your door with nasty paperwork.
Have you thought about sawing it into managable pieces? Looks like you can get at both sides once the water is gone. A couple of local college kids that have made it into the big time. My employer has used them many times usually for sawing pavement but we cut down a bridge abutment with one of those wire saws - neat stuff. http://concut.com/services/
I definitely think I would rent a bigger hoe/hammer. Why beat yours up? IF that's the route you go.
Well, guys, it sounds like this project is going to happen this fall. The last permit will be in place in a couple weeks, and as soon as the ink is dry, it's going to be go time. I was never able to locate anybody to give an estimate on blasting it, so we're going to have to use brute force. I've been thinking over many scenarios this summer, and I'm down to two possibilities. First one is to break a small, narrow hole through the dam to let the water off, second is to push out a coffer dam and bury a 36" pipe to drain it off. The water is about 6' deep on the top side, so installing a pipe wouldn't be too bad. The dam itself is pretty crude. It appears they just basically "piled" a softer mud-mix, no rebar, and blanketed that to form the spillway. The blanket layer is only about 6" thick, and contains the only rebar except for the wing walls. Upon further inspection, about a third of the core under the blanket is completely gone. You can look in THROUGH the south wingwall, and it looks like a cave for about 30'. My main question is this. If I choose to break a hole to let water out, should I be worried about the wall holding the water giving away while I'm trying to break it out? My initial plan is to break up the spillway where it's eroded out underneath, and kind of fill the void in with the broken concrete, and then open the water side and let the water run through there. I'm thinking of about a 3' wide hole to start with, can a hammer be used in water past the punch part?
Dig a shallow bypass spillway, deepen it by stages until the water is low enough, then drop your pipe in and backfill. Just to prevent the tidal wave effect swamping someone else's land.
There is about 300 acre/feet of water to let out. I don't believe I can get away with letting the water run through a dirt trench.
Just a thought, you could make a siphon to lower the lake before cutting the dam of spillway. I have a 3 acre pond and I have made a 6 inch siphon to lower the level to work on the dam. I have a 30 foot drop over the back of the dam and the water comes out faster than a fire hose. I could drop the pond 3-4 feet overnight. I don't know all of the particulars of your job, lake size, what is downstream. Depending on materials that you may have on hand or get cheap. Setting up a couple of 10 inch siphons you could lower a pretty big lake in a few days and have control of the situation. But, if there isn't any worries about whats downstream, hammer a few holes through where you say it looks hollow and stand back. Good luck!
I think he meant to use a culvert buried in a trench through the dam. I'd go right through the dam like you're talking about. You know your terrain there, six feet of drop is not what most people are expecting when you said a thousand acre feet up thread. If the water somehow washed out the slot in the concrete it's going to back up pretty quick so you'll have four feet drop, the water just won't wash through there as fast as gcdoty's 30 foot drop. That wall collapsing from the water rushing by would be the least of my worries. IF that dam is undermined where you drive an excavator over the top of it, that might cause it to be unstable, but if the water hasn't moved that dam yet, it's not going to move it when you have three feet open. I'm thinking that is going to take a lot longer to drain than you think, like a couple days with a narrow slot. I'd probably go out there with a sledge hammer and knock a couple feet out of the upstream side where it looks hollow, come back in four days and check the progress. Rather than leave an excavator sitting waiting for the water to go down. But then I'm not in your business.
Thanks for the input, Delmer. After your post, I realize I haven't posted what the plan we were able to find listed for the size of the pool. The plan said 70 acres, so I'm thinking 300 acre/feet might be more realistic?
I watched a crew a few years ago take out a 150' dam that was a about twice as tall as yours. It was too narrow to drive on, so they build a rip rap road at the base of the dam and hammered a break in the dam on the far side to drain. They used some of the concrete to shore up the road from time to time. They could only get one excavator at a time on the rip rap, so they would hammer some and clean up some. I did have a few pictures on my phone, but that was two phones ago.
That's basically what my plan is, if I need two excavators, I can recruit another, but I'm hoping to maybe do it with one? I know most all of you guys recommend having 2 machines, but I'm going to rent a hammer for a week, and I've had a couple of guys visit the dam personally. Both agree the concrete is rotten enough I might be able to tear open the drain hole with my ripper tooth, and potentially alot more. One of the guys did a fair bit of concrete removal in the MSP area, and he feels that 20-25 hours is going to be plenty to break it up. There is only rebar in the top 6-8" of the concrete. I can dispose of any/all the debris I choose onsite, as long as no rebar is exposed. In regards to leaving the hoe onsite while it drains, I plan on doing some scraper work while it's draining.
Gcdoty, I'm not sure why I hadn't seen your post until now, but thanks for the siphon suggestion, I hadn't thought of that. So, can you give me some info on a siphon? What kind of pipe, how to set it up, get it flowing, etc. Downstream issues are not going to be any sort of problem, this dam is on a river, and I personally have seen water going over this dam 2 FEET deep for days at a time.
I've done one siphon using 10 inch black flex drain pipe its rubber gasketed, got some 20 foot lengths made a plywood plug held in one end with drywall screws, then fill the pipe all the way, keep both ends submerged and pull the drywall screws and get ready for a torrent. It was a little tricky getting the pipe filled using a trash pump but with some careful lowering it all worked well.
Any wild guesses how many gallons per minute it was moving?
You can use this calculator, just need to figure out what the water drop is from the siphon suction to the discharge. http://www.calctool.org/CALC/eng/civil/hazen-williams_g Doing some fast calcs, using a 10" pipe, with 6' drop and 30' of pipe, it would take around 10 days to drain 300 acre feet of water... my math could be wrong so take at face value.
So is this just upstream from the junction with a larger river? It doesn't look like any flow besides leakage in the pics? In any case, it seems like very low risk to knock a 3' slot in the dam and let it flow, a day or two should drain it as well as it's going to.
Not really. The James River flows completely through SD before joining the Missouri River. Here's a topographic map of the area. The dam is the black line through the river. http://map-pass.mytopo.com/maps/pri...lat=47.683335&lon=-99.452067&orient=1&res=144 No, it's not flowing right now. Just a little trickle from what I could see this morning.
This video is pretty interesting. Just a little bit more dam than the one I'm going to do. https://youtu.be/HNJPtYJ4THg
I was expecting an arch dam high up in the Alps. That dam of yours is funny, 5' contours on the map and only one of them crosses the river in about 3 miles? If you had a large enough crane you could pick that dam right out of the channel and there wouldn't be any significant flooding from the looks of it. Take a look at a topographic map of Victory WI. We had some rain a couple days ago and there was a fatal mudslide. All the local dams held though.
Looks like a fun little job Shimmy I like your idea to rent a hammer for your excaavtor and then use it with a bucket to clean up. 40 hrs with a hammer should be more than enough with what you have posted. As for a drain, the siphon works. I have worked one with 12" HDPE pipe, and charged it with a tee at the top with a valve, and a water pump. instead of the wood screwed over the end I would use a test ball for air testing serwer pipe. You can usually rent them from a pipe supply outfit. Air it up to seat it, and when you get the line charged with water, release the air and the ball will push out. Have a rope on it for retrieval. I did not check the chart, but the one I was doing would drain +/- 20 to 25 acre feet per day with a 12" line. Good luck to you
Finally going to get this show on the road. I'll try and have some of the guys get some pics. We're going to make a hole in about an hour to start letting water out. Should be fun.
Good luck! I look forward to seeing the pics
First opening made. Went back this evening and made it a little bigger.
She's a third gone, haven't had the need for a hammer yet. No wonder the State said it needed to come out. I've spent a total of about 3 hours. Should come out on this bid, LOL.
Just curious, was this a depression era civil works project? I've seen a similar one in SD. Ed
Looks good Shimmy. Thanks for posting the pictures. Its always fun when the job is easier than the planning.
Yes, it was a WPA dam, built sometime in the 30's. We have one record for it, a plan sheet dated 1930.
Looks like a pretty good win alright!
This is the first I've seen of this thread. Sounded like a cool job, but after reading the first page I had a big fear of what the rest of them were going to look like. I once did a job where they decided that concrete was cheaper than dirt and we had 2 foot thick concrete on it. It took out 210 with a hammer 10 hours to break up a 10 ft Square. Even then you had to work a cat 336 hard to pull thought the rebar.
We are going to try and keep going with the ripper. Hasn't been too hard to work through it, and I don't think a hammer would be much easier on the hoe. My ripper is pretty stout, and the top is pretty rotten. I've just been poking some holes, and I can pull out 3-4 foot slabs pretty easy. Then just wiggle it around to snap the bar, grab it with the thumb and lay it down in the pool. The plan right now is to get the concrete with rebar all leveled out in the pool first, then cover it all with 2-3 feet of riprap. If the pool isn't deep enough, we might have to try and lay the rubble up into the bank on the right side of the pics, cover with some dirt and then rock. I bid $10,000 to break up and place concrete, importing in more rock is extra. I think we might do pretty good on this job.
I just went back and read through the posts from last summer and found yours, Delmer. I had more than a few people call me nuts for walking the hoe out in front to breach the concrete. I'm pretty sure you were spot on saying that if the water hadn't moved anything yet, it wouldn't with a hole in it. Ended up only being about 4 feet of water behind it, which is right on track with what you said after I posted the link for that topo map.. I breached it at 9:00 am Tuesday, lowered the breach another 2' at 7:00 pm, and around noon Wednesday I had a third of the dam on the water side completely removed down to the dirt. Right now the water is running about like a 3' CMP, it's slowly washing itself a channel through the silt layer. I still have the spillway fully intact on the front side where the water is running, not sure how deep of a channel it's going to make.
First time I've seen this thread. One of the oldest posts on one of HEF is a New England outfit that repairs old hydro and dams. The Clinton dam recertification process had them demoing them instead of keeping them making power. Glad your project is going well.
This project is all wrapped up. Was able to process all the concrete without having to get a breaker. Had a couple tough chunks, but since getting a hammer would have required a couple 250 mile round-trips and quite a bit more messing around switching back and forth, I feel toughing it out was the right plan. Took a day to completely demo it, a day with myself and another guy cutting and picking up rebar, and today to smooth off the sides and put the finishing touches on.