5000 SF Pond Renovation (Muck Removal Via Gold Dredge)

IHDiesel73L · Jun 19, 2020

I started posting here a while back about our small pond and started getting some good information but work and other things got in the way and I had to put it all aside. My attention has turned to the pond once again and I've come to the conclusion that job one has to be removing as much muck and silt as possible. Since there is no life beyond frogs and turtles in the pond currently I have no worries about releasing toxic gases into the water. My goal is to accomplish the following:

Thoroughly clean the bottom and sides down to a plain soil/rock bottom.
Line tributary/runoff channels with geotextile fabric overlaid by 3-5" rock.
Line "soft" shore areas with geotextile fabric overlaid by 3-5" rock.
Run PEX air line into pond and begin aeration.

Here is a diagram of the as-built conditions of my pond. Essentially it was simply dug out of the edge of a swamp with the spoils piled around the south and east sides to form a dam. As far as I can tell it is mostly filled with groundwater as it was basically just dug below the water table. In three years I've never seen the water level drop more than 3" from the top of the standpipe even in the driest spells. There are two runoff channels/tributaries that run into it that probably contribute most of the silt, so I want to try to trap that further upstream and line the channels with rock so that as the water flows down the silt gets scoured out of it. We have an old farm property so there are old stonerows everywhere from which we can "mine" all the rock we need from. In any event, I know that oftentimes a concern of removing muck is getting water back into the pond, but I don't think that will be a concern for me. Rather, I think it would be a challenge to fully drain it:

My dredging plan involves building a modified "gold dredge" in that instead of my discharge going into a sluice and back into the waterbody I'll simply discharge it to the swamp that sits below the berm:

If you're not familiar with how a gold dredge works it is basically a venturi pump-you pump high pressure water up a hose which creates suction upstream-since all you have is a column of water and debris moving through a 3" hose there are no impellers to clog, etc...so it will handle anything small enough to fit through the hose essentially:

Based on my reading I think that this Harbor Freight 2" semi-trash pump should do fine for my purposes since I really don't have much head:

2 in. 212cc Gasoline Engine Semi-Trash Water Pump - 158 GPM

I sourced four free 55 gallon poly drums from a local carwash and will be building a platform on top of them so that I can float the pump out into the pond, keeping my lines shorter and thus cheaper. I'd be grateful to hear from anyone else who has undertaken such a project about tips, pitfalls, etc... Based on measuring that I've done from my canoe I have about 6-7' from the surface to the beginning of the muck layer. From there its not clear how thick it is and what underlays it. I would love to be able to increase the depth to 8-10' feet in the middle but I'm not sure if that's realistic given what I have to work with. I'd love to just rent a trackhoe and begin scooping out a yard or more at a time, but the pond is way back in the woods and just getting the machine back there would be a challenge. Also, I will probably spend far less on my dredge rig that I can use indefinitely than I would renting a good sized machine for few days with delivery, etc...

lastride · Jun 19, 2020

Interested, going to follow this thread

Xfaxman · Jun 19, 2020

Also following, good luck.

IHDiesel73L · Jun 20, 2020

Xfaxman said:
Also following, good luck.

lastride said:
Interested, going to follow this thread

Thanks-probably will be a little while before I start as I have a woodshed and a chicken coop to finish before I start on this. My overall goal is to make the pond a pleasant place for my kids to fish and/or cool off. My daughters like to eat their lunch at a little picnic table we have down there for them and they decided to sit on the bank and dip their feet in. My older daughter ended up getting a leech on her foot which she was not thrilled with :laughing: After doing a little research I found that getting rid of the muck and stocking the pond with a healthy fish population will reduce or eliminate leeches as they like to live in the muck and they are a food source for many species of fish. A zip line or rope swing is also on the list.

3Ts · Jun 20, 2020

I will be interested in how this turns out as well.

Two issues:
First, what is your in-flow rate of water? i.e. How fast does your pond fill? Your configuration is going to use the water in the pond to create a venturi to suction more water and dump it outside the pond. So all the water that you're pumping plus more will be pumped out of the pond. You have around 30,000 cuft (50*100*6) of water or about 224,000 gallons (30,000*7.48) which means the pump will suck it dry in less than 24 hours. Since you said the pond only drops 3" in droughts, you'll probably be fine as long as you're not in a hurry. Just keep tabs on the water level as you work on this.
Second, all that muck you're pumping out has to go someplace. Since you're pumping it into a swamp will that be an issue? Depending on how that spreads out, you may be turning the swamp into dry land.

chim · Jun 20, 2020

Another approach would be to use a sediment / dewatering bag. and return the filtered water to the pond?

ovrszd · Jun 20, 2020

Curious to see this work. dirt silt is extremely heavy and dense. I would assume it will require water/silt ratio of maybe 5 to 1 or maybe even higher? Will empty the pond long before the silt is excavated?

EddieWalker · Jun 21, 2020

I admire your creative thinking to cleaning out your pond, but in my opinion, you are wasting your time trying to get the silt out of the pond with a pump. There is only one way to get silt out of there, and that's by picking it up and carrying it out. A dozer pushes dirt and it wont work. Your options are a tractor with a loader, which is how I did it on my pond. It's slow and you get stuck a lot. A track loader works better, but it's also slow unless you get a really big one that can do 3 yards at a time. But that's really expensive. Then there is an excavator. A long reach would probably be the best choice for this project, but it's expensive. Any other excavator can do this, but they cant haul anything, so you need a dump truck to move the material. Finally, there are dredge lines, but that's probably not an option for something this small.

Two ways of doing it. First, you pump it dry, wait all summer for it to dry out some more, and then dig a ramp into the pond that has a solid base to it so you can drive in, get a load of material, and back out. Do this until you can turn around inside the pond and not have to back out anymore. I had 2wd, and backing out didn't always happen for me, which lead to more time, more issues, and more frustration.

Second way would be to remove part of the dam, and let it drain out, along with as much silt as you can get to flow out of it. Hopefully the dam is deep enough to get below the silt. Then wait all summer, and do the same with a ramp into the pond and start hauling out the silt.

Odds are very good that you will have dozens of yards of silt to haul out of there. On my 3/4 acre pond, it was hundreds of yards that came out.

What are you going to do with the silt? Piling it up close to the pond means that it will wash back into the pond. the farther you haul it, the more time it will take. It will take a full year to dry out to do anything with it, unless you spread it out, which is more work and time.

SPYDERLK · Jun 21, 2020

It might work some with a trash pump - - but I think you will be very inefficient unless you stir the muck at the suction point. I think you could do this with a pressure washer. You would have to supply clean water to the washer.