Hi everyone- So I posted before about a property with a pond I am looking at buying. thanks for the amazing feedback so far!
See attached photos for seepage issue. The pond is 6 acres, dammed with an 8ft earthen dam built in 1965. The current owner had it for 30 years and didn't maintain it. The standpipe rusted out and was filled in with dirt so outflow is over a vegetated spillway. There are some large trees on backside and toe of the dam and woody brush. The pond is springfed and completely full, with decent flow over the spillway. The springs feeding it must be strong enough.
Clearly, I have to remove smaller trees and brush and bring back to grass. Not sure if you can remove large trees safely. Am I looking at complete rebuild, spot repairs, or just bring back grass and watch it? Can these things be stable years an years, or is this the beginning of the end? The photos are after a snowfall. Several spots on the dam look like seep. One area is below a large tree, roots I guess. No gushing water, if there is a trickle its hard to see. Take a look at photos, comments welcome.
Goal is pond full of water to kayak that won't collapse. I am not afraid to invest in this, but dont want to rebuild it if not necessary!!
If all ur wanting is a place to kayak around! Sounds to me like you already have that. If it was leaking more than inflow there might be a problem. Repairs could be made but prolly not an immediate issue. I'm not an expert here just my thoughts.
I asked the same question when we bought this place. It was suggested that we remove trees less than 4 inches in diameter and leave the larger ones. It seems I have a small leak as well but it doesn't seem to be significant enough to require a repair right now. That looks like a beautiful place.
Trees on a dam are not a good thing. Here's why. The roots can cause highways for water to follow through the dam. Typically in a situation like yours the recommendation is to cut down every tree smaller than 4" DBH (Diameter at Breast Height), treat the cut stumps with a herbicide so they don't grow back and leave the larger trees in place, hoping that the roots don't disrupt the structural integrity of the dam.
Tree roots will die and decay, leaving paths for water to follow. Just like tree roots getting into septic lines or growing under sidewalks/driveways, they expand as they grow, pushing soil out of their way, compromising the integrity of the dam. The dam should have a packed clay core trench if it was properly constructed. See the following link for examples: Dam design examples
I'm not saying that the dam will fail, but I am really leery of having a leaking dam. It won't fix itself.
Plus you don't know how much water will leak out. Think of a bathtub. All is fine and dandy when the plug is in place. Incoming water will fill the tub, when the incoming water stops, the tub stays full. If the plug is pulled, the incoming water cannot keep the tub full any longer.
The problem with a leaky dam is that you cannot determine if the hole in the future will stay small enough to keep the pond full. I'd hate to see you pour a lot of time, effort and $$ into the pond to get it just the way you want it to see the plug get pulled out one day.
Thanks, I agree about the trees. should an 8ft dam be pretty dry top to bottom on the backside normally, or is some seep normal? I think the springs pretty and will keep it full even with leaks. I think my main concern is potential for failure, and just getting worse fast.
I dont mind spending some $$ now, like 20-25k to bring in dirt guys to drain it, remove trees, new drain pipe, add bentonite to front face, etc, if this range +/- will do the work needed. I can spend some money to get it nice, so I can keep it maintained for the next 20-25 years. What I dont want is the 50-100k pricetag for a do-over. I just have no idea how much dirt 10k, 20k, 30k moves? Im in NY in a rural area, not down with the rich city folk.
Jim, we've been here just over 5 years. I have a small stream that runs constantly at the base of my dam. We have springs here and I have at least 2 that are filling the pond. Our extension agent isn't certain that it's leaking but thinks that it's more likely than not. Since it's staying pretty full, I'm watching it for now. Even during our drought, it only dropped about 2 feet.
If you're willing to spend that much money, I would have a highly recommended professional evaluate it entirely. Measure depths, dam length, etc and provide an estimate to fix the leak and replace the pipes. Sounds like an awesome pond and worth at least a close look.
How are you going to know unless you try!
NW TX 2ac main pond fed from 1100ac watershed going through 2 2+ac sediment ponds. 1st filled 10/2018 900BG, 200RES, 200HBG, 100CC and 23# FHM...."Free" BH, GSF GSH, LMB & ??? 75LMB 3/2020 I subscribe!
One thing you might want to do is get a boat and marked pvc pipe and check the depths all over the pond.
If it is silted in and only a few feet deep or if it still has plenty of depth might make a difference in what you decide to do.
Six acres is a nice size pond! If you have good depth, would it be possible to clean the current dam, then build a completely new dam with core trench behind it? (double the width of the existing dam). This is not a recomendation, but only a question and something to think about. Lay of the land, where the dirt would come from, etc all questions that might not make it work. But dams of old were often made only wide enough to hold the water back and might enhance the pond to have a much wider dam.
I had an old cow pond with narrow washed out dam. I cleaned it out, enlarged it, and made a nice wide dam I could drive on and mow the back side (it was too steep to mow safely originally).
If the pond is shallow and silted in, would be much better to fix that problem rather than just fixing the dam.
I'm definitely no expert, so only raising questions for you to ponder. Not making suggestions for you to do.
A couple of questions I have is in picture #2 there are some rocks in the picture, what are the odds of your ground being rocky and may be the cause of the leak, unless they were placed there by man afterward for some reason or other, also the dam looks really small and shallow to be holding 6A of water, if the dirt is of average dam making quality it shouldn't be too bad expensive if you had to redo the whole thing.
All the really good ideas I've ever had came to me while I was milking a cow.
When the cost of rebuild becomes too expensive for your wallet, IMO keep downsizing it until it gets within your wallet $$. Get a contractor that knows how to use a pull behind double barrel sheepsfoot roller or sheepsfoot mechanical compactor to compact the pond bottom assuming you have good clay. If he says he doesn't need it then switch contractors. This is very good leak insurance that is relatively cheap insurance. I would never spend good money building a pond without a sheepsfoot roller. The risk and cost is too high to get leaks with just dozer compaction unless you have excellent clays. Hundreds of members here ask questions about fixes for their leaky pond.
As esshup said - Trees on the pond banks or dam is like having small drain straws surrounding your pond!
Rule: all dirt leaks even the very best clays; the variable is how much is it leaking / seeping / wicking? I know well sealed northern rock/stone lined ponds that only loose 12" of water (mostly evaporation) during a drought year.
Last edited by Bill Cody; 01/05/2008:01 PM.
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I agree, the dam just looks too narrow to me for the a 6acre pond. The dam is only 8ft and 240ft long, and the crest is like 6ft. I too wonder if one can drain the pond, clean, compact on upstream face, and just double the dam thickness downstream adding on to it? Property has 70acres we should be able to source dirt somewhere.
Great advice. This forum is amazing, what a resource should I buy this place. Do you think at a minimum, I'd drain the the pond, clean, add more clay, and compact the upstream face. While empty, remove trees, grub stumps, pack holes, maybe add some fill downstream toes to thicken the dam? Just need a dirt guy to do it.
Try and use the poor existing condition of the pond as a good reason to make some amount of lower counter offer because of the pond's devaluation (poor condition) because owners did not take proper care of the pond. Now, any new owner has to pay for the current owner's pond neglect, thus they should accept a lower price.
A good contractor with proper compaction equipment can breach the dam and implement your rebuild ideas. Before you finalize the sale try and get at least one reputable contractor to give you a work dollar estimate so you have a rough idea what it will cost.
Last edited by Bill Cody; 01/06/2010:22 AM.
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If I were to guess at the construction of the dam, it wan't excavated down to an impervious layer to build a keyway before being built. The seepage you are seeing is water making its way through non-compacted soils under the dam.
If I were to buy a little "insurance" and wanted to assure another 20 years of decent pond, I would do as suggested:
Test the depth of the pond. If adequate: 1. Remove or make more permanent the disabling of the old drain. 2. Remove trees, stumps, roots as much as possible. 3. Create a new key-way and dam behind the current dam, re-enforce the dam and widen it, compacting properly. 4. Install a siphon system drain with a bottom draw.
If not adequate depth: 1. Remove old drain, drain pond out gap. 2. Wait a season for the muck to dry out as much as possible. 3. Excavate pond basin, shove muck out the gap on the backside of the dam. 4. Steps 2->4 above
Or Optional elevate the new dam to gain depth instead (may cost less). 2->4 above
Cody's note: also IMO remove a majority or most of the trees and brush around the pond. Every tree there has contributed to the amount of muck and slop that is in the bottom. From the pictures it appears there are easily 3 to 4 ft of muck as mostly dead leaf matter in the pond belly. Tree leaves shorten the lifespan of the pond plus add nutrients for plant growth depending on how many leaves enter the pond. Leaves are rarely good for long tern pond ecology.
Thank you Bill. I ended up buying the property with the 6 acre pond. It's amazing, and got some discount there. It's gonna be hard work to restore it, but it will be worth it. Subscribed to the magazine, can wait to get it.
Tree roots tend to grow towards water. I would think that tree roots from the down stream side of a dam would be those most likely to go through the dam. Trees on the up stream side would have no need to extend their roots through the dam to seek out water. Conifers have a relative small root ball so should be less of a problem. As a rule of thumb, the roots of a deciduous tree extend only a little further than the tree canopy. The exceptions could be trees like willows, cottonwoods, and silver maples that could have roots searching out water much further out than their canopies.
I was taught the same thing about deciduous tree root span, but have never found that to be true. Perhaps in rich soils with consistent moisture. The reality is I can be digging out in the middle of the yard a long way from trees, and hit some fairly large roots questing for moisture and nutrients. Trees like Oak, Maple, and Ash.
Then there are root spreading trees like Aspen and Sumac. I can find roots from Sumac in New Zealand from my yard probably. Those quest everywhere, but are typically quite shallow. I find them fairly thick in my raised bed gardens and the kid's sandbox after only one season.