Greetings Tim and everyone, I am looking for advice on building a "dug-and-dammed" embankment pond in a primary valley keypoint at my homestead. The existing slope is 25% and the soil is mostly a well-draining, fine sandy loam with 12-16% clay. The dam would be 10-15 ft high and 75 ft long. At the outset, I am feeling discouraged about my prospects of using solely this material for an earth dam and achieving a proper seal on the pond. Without trucking in a large amount of clay, is there any likelihood that this scenario could work? I suppose I could try gleying or wallowing pigs in the pond itself, but I wonder if those methods would actually succeed, and first I need a solid dam.. any advice would be great. Thanks!
I would say highly unlikely that such a dug and dammed pond would seal with a sandy base. You need good heavy clay. However, anything is possible! I would also be concerned about installing a large dam in a primary valley, as you cannot control the inflow, and may flood your dam during a freak weather event.
I would check out the PondBoss forums, at http://forums.pondboss.com/ The community there is incredibly knowledgable and friendly. Ask away with your questions, folks are glad to help. Definitely get a good plan, endorsed by experts, before you start moving dirt. Ponds are easy to make a mess out of, but done properly, they are incredibly satisyfing. I completed a similarly sized pond just over a year ago and it is awesome. Trout are jumping, kids are swimming, and the farm is better irrigated that ever. It is worth it!
Good luck and let us know how your plans progress!
Well, small world... I just invoked liners in an answer regarding earthquake proofing a pond... and one of my first suggestions here would be
to consider, if you have little faith in water retention capacity of soil, is to consider a liner. Perhaps the primary question is, who's gonna build it?
You? If so, how much experience do you have, and what equipment? I rarely see folks building their own ponds unless they are pretty
accomplished dirt workers. And then they might not be asking those questions. Of course a simple hole in the ground might work. But if you're serious about a solid creation, I'd look around the
neighborhood for smart and successful builders, check out their ponds, see if they've done something similar to your project, and have them
check out your site. Here in Vermont and the north country, half the battle is getting a savvy pond builder on board. The other half is coming up
with a good site, avoiding permitting hangups, and paying the bill. I agree with the suggestion to check out the pondboss.com forum, read up on related topics, and
put out your questions there. That said, it's really tough to evaluate a pond site/plan long distance... although it can be done with phone calls,
Tim, how would a liner function with a dam? I always thought of liners as used primarily on flat ground with excavated ponds, but if a dam is necessary, would you install the liner inside the dam? I am attaching a link to a google earth file, in case anyone wants to look at the layout of my site. Download it here: pond. It shows the property boundary and the proposed pond site, with some 5' and 1' contour lines added.
Liners need smart installation. They can be used with a dam. But you have to be careful that slopes are flat enough so that protective covering if used
doesn't slide to bottom of pond.. like small stone which is often used. Sand sometimes. I've seen people get in trouble with steep slopes and sand or other
protective covering sliding to bottom. However, I know contractors who put liners on steep slopes (including the dam).. with no protective
cover except the top 5 feet or so which is angled flattish, then the slope goes steep... that requires a shelf at bottom of the 5 foot slope, so the top
5 feet can be covered, in this case with earth, then the liner goes down uncovered. Many other aspects to liner installation that not all contractors adhere to,
but include underdrain(s) to drain ground water (if there is any) under liner, and piped to outside of pond... tricky to do but otherwise ground water
can lift liner and displace it... recovery of ground water sometimes a very helpful thing, so drain(s) have to then go to a cistern outside pond, to be
pumped back... mustn't neglect to mention protective underlayment (sand, construction fabric)... again, some don't use, but if soil has sharp rocks, well
you can imagine... of course liner itself should be thick mil, say 30/40 mil, and uv resistant....you may be able to get good install info from liner suppliers..
or pondboss.com forum....in perfect world you won't need a liner but they do allow people to build where it wasn't practical before... and if wetland
permitting nixes best site, you can move to drier location and use liner... next question of course may be, what do you use for water if you've gone to dry site... another topic.
Hmmm.. the liner in the dam setup sounds pretty complicated and deserves some pretty involved engineering. I think I need to call in reinforcements! I would call Sepp Holzer, but he would probably charge more money than I can make in a decade. If anyone has recommendations for pond construction gurus with steep slope expertise near Asheville, NC please contact me. Thanks for the advice, Tim.
check in at the forums at forums.pondboss.com Lots of experts there who are glad to help, definitely some in your neck of the woods.
Definitely consult with some experts for a project that large, the results will be worth it!