Pond Boss Forums POND CONSTRUCTION Building a dam Ridgepoint Dam Construction and keyway/core trench

Hello! First post. Let me introduce myself...My name is Eric. I live in southwest Missouri and own 10 acres. We average 43 inches of rain here a year and its a zone 6 climate. Hot humid summers and cold wet winters. I'm a certified permaculture designer and took my permaculture design course, reading the landscape and earthworks course through Geoff Lawtons online design class last year. I am currently implementing my permaculture design. There is a lot to my plan and my story so I'm going to give you some back ground before I get into the pond question if you don't mind.



This is the contour map of my property and my neighbors property right below it. Mine is at the top in yellow.



Here is the satelite image of the same property.

And as a reference here is my permaculture design as I would like to implement, but i'm making some changes, its all fluid at this point and not set in stone.


I purchased a transit level and surveyed all the property and studied the patterns of the landscape quite closely over the period of three years. I've had a well drilled into the top of the ridgeline, its a "simple pump" brand well pump, I can drive it all off of the solar system I am installing.

I had a building pad built and built a 40x50x12 all steel building on top of the well and will build a house on one end and my shop on the other. Cooled from what I hope to be geothermal from the well. A few pics





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Now on to the pond! The things we all love! I was excited for the building but I'm more excited for the pond. I have the perfect landscape to create a ridgepoint dam. A place that no one ever thinks to put a pond because it has zero catchment. In permaculture they teach us that everything must have at least 3 uses. My goals for the pond are, one, To use the light reflecting off of the pond to help me gain more solar energy, both in my solar panels and heat gain in the winter, two provide irrigation for my gardens and tree growing systems, and three I would like to use it grow fish to feed my family. I intend to fill the pond from three sources. one, the building itself, in 1 inch of rain I can expect approximately 1700 gallons. Two Giant swales will be cut on contour all around the property that will collect water and run it into the pond, and three, I can pump water out of the well, all day long, as long as the sun is shining.

Due to it being a ridgepoint dam and not in a valley, it will naturally take on a kidney bean shape as the land is higher in the middle of the ridge then the points. I have surveyed it out and its going to wrap entirely around the buildings SE and E sides. I'm shooting for a .25 acre pond with a depth of 8-12 feet according to the nrcs.

Here's the area the pond will be, i've been moving my 3 years of accumulated junk to make room for it

[img]http://s6.postimg.org/4czthxsmp/20151101_101454.jpg[/img]
The giant hole in my front yard was where they robbed clay to build the pad. Bieng Im on a ridge and constructing a ridge point dam I have an abundance of material. I performed a soil same and I'm very close to pure clay in alot of parts, so the ponds a go this weekend.
[img]http://s6.postimg.org/lqwma4pwx/20150905_123744.jpg[/img]
[img]http://s6.postimg.org/bi454b1v5/20150907_125731.jpg[/img]

Here is my question. How deep should I dig the keyway or core trench. At each corner of the dam, the bank will be 3 foot 4 inches higher then original ground level and 1 foot higher in the center of the ridge then original ground level. The dam wall itself, will become the driveway to the shop and approx 12 feet wide at the top with a 3 to 1 slope into the pond and most likely the same or a little steeper on the back slope. the back slope will be planted in bamboo to lock the dam into the landscape and for ease of maintenance. "Plus" i can cut bamboo stakes for use in the gardens and tree markers, but you guys already knew I had a third reason

I know I was taught to build core trenches in my earthworks class below the bottom of the pond, and that makes sense to us for common valley dams, the most common type of pond, as you need to "LOCK" the dam into the landscape and prevent seepage.

But I was not taught about core trenches on a ridgepoint dam, as they are not common at all due to the zero catchment. So should I take the core trench all the way below water level, even though 80% of the dam is going to be below original ground level? I almost bet I really only need to go probably 6 feet down or so to act as the mechanical lock and then just compact and compact layers and layers of clay. Opinions? Even if it seeps a touch I can correct that easily with ducks.

Im so excited. If I get this right, since sediment cannot build up in this pond, if I get these earthworks correct, I will have a pond and swale combination that could be here for hundreds of years repairing the earth around it. Thanks for looking at my post!

Interesting idea. I have zero experience in this.

How do you correct a leaky dam with ducks? The pics show the land to be rocky so I expect the entire area will be somewhat permeable.

What are your plans for the rare but occasional 6 to 8 inch rain when the pond is already full?

You mentioned using the pond to feed your family. Any thoughts on how many lbs. of fish you are envisioning for this scenario? (How often are you intending to eat fish)

The water level will be controlled in the swales. A swale is basically a giant ditch cut on contour so its completely level throughout the property. Its uncompacted topsoil that forms a mound on the down hill side. Its a tree growing system that hydrates the landscape. There will be a culvert that runs east and west through the driveway that leads to the shop doors. That culvert will connect to a swale on the other side that runs east as far as it can until I run into straight forest. In this swale will be a level sill spillway that will passively discharge excess water. By controlling where you cut the mound of the swale for the spilkway , you control the water height of the dam, and you can direct that water in whatever direction you desire, in this case, to help fill an older poorly constructed pond downhill. As rains water flows across the property it gets caught in the swale, since the swale is level, water will flow into the pond at the end of the swale until the pond is full and then once the pond is full, water will back flow into the swale filling it up to the level sill spillway and then discharge. Once the rain stops the water in the swale soaks slowly into the mound and super hydrates the landscape. There will be a second swale attached to the pond that runs to the north fence border. One this swale there will be another spillway, quite wide and 6 inches higher then the other spillway. There will be no culvert between this swale and the pond and this will serve as the emergency spillway in case the culvert plugs at 2am while I'm sleeping. The primary spillway will set the freeboard at 2 feet max water height and the emergency will be 1.5 feet freeboard. I deem this an acceptable amount of freeboard on a ridge. If it were a valley dam, the minimum freeboard is 3 feet.

As far as sealing a pond. There are several methods. I've personnaly ran pigs in an old pond that use to dry up and it held water all year, however the pigs are quite destructive and I would never own them again.

Ducks I have not tried personally but I have spoke to many people and my mentor has done it. Its similar to gleying a pond if your familiar with that technique. Basically you get a whole bunch ducks and let them poop in your pond for a year or two. The duck has a very fine manure that breaks down into small particles in the water and are pulled into seeps in the pond walls as a thin layer builds, over time the ponds seals.

There are ways to do this with cows etc. But I have kept ducks before and they are most likely the easiest animal to care for.

I encourage you to check out geofflawton.com and sign up to see his free videos. There is one where he explains the process of sealing a pond with ducks.

Its worth noting at this point. Swales are tree growing systems, you plant forest on them. Mine will contain fruit and lumber trees. They fully hydrate the landscape, springs will pop out downhill around 7 years after installation.

As far as how much fish I expect to produce, the answer is, well not much, I don't really care for fish. But it can never hurt to have another source of food sitting in your front yard

edited because I cannot spell

Eric, you may be the first PB poster who actually intends to encourage waterfowl to poop in his/her pond.

Really? People don't want duck in there ponds? They have such tasty eggs, seal your pond, suppress weeds like duck weed ( go figure, its an very healthy forage for them and they control it) and dependin on the species you choose, can be very tasty. Some duck meat is just not good. I don't care for a greasy Peking duck. All in all its a total win. I'm not sure why you would discourage water fowl from your pond

Well, allow me to enlighten you. Waterfowl are parasite vectors for fish, and their poop is an excellent fertilizer for encouraging unwanted plant growth. In addition, they may bring unwanted and invasive species of plants into the pond also.

In a neighbors 1/4 acre pond, a single pair kept the water muddy with their constant dabbling around the pond edge. Once the coyotes removed them, the water cleared up.

As for cows/pigs/ducks sealing a leaky pond, I would not stake my reputation on having that happen frequently enough to consider it to be a reliable way to seal a pond. I'd rather place my money on a sheepsfoot roller and clay.........

Depending on the amount of ducks in the pond, if you were going to use the water for fertilizing/watering purposes, and using the ducks for egg production, then I don't think having them in the pond would be bad. But having them in the pond, and either using the pond to swim in, or eating the fish out of it? I wouldn't. But that's just me.

Eric, I agree with Esshup. The downside to ducks in a pond is always greater than the benefits. The fouled water might be good for fertilizing plants but I don't know anything about that.

I do know that duck manure fouls ponds enough to kill fish. They essentially turn your picturesque pond into a sewer.

Ok guys, I like having ducks fly over the pond and I enjoy seeing them circle overhead while looking for a place to land. And I like Busting a cap in their arse just before they land. Ducks are good during hunting season. Some ducks are fish eaters and I don't like those

Tracy

I think it's all a matter of priorities. What are the goals for the pond, and what concessions need to be made in order to "have it all".

No waterfowl of any kind for me, but that's just my take on it. As someone interested in growing fish, waterfowl make too much extra work and are just too risky for my liking. I consider them to be bucket stockers of a different sort.

You also have to remember that the ducks do not need to be there permanently. Evaporation is around 30 inches in this part of the world. If you put 25-50 ducks in for a year and keep track of rainfall and the water level of the pond. If the leak is fixed you don't have to keep them. Stock your freezer with duck, stock a bunch of fish and feed their entrails to the fish.

There really is no such thing as an "invasive" plant. Its just a plant that finds a niche that is not already taken up in your newly created ecosystem and thrives. If you fill that niche before that plant arrives it cannot grow, there's no space for it.

But you really cannot battle mother nature, she has a set number of rules you must play by, or your stuck in a cycle of burning/slashing/ and poisoning to control plants you don't understand

25-50 ducks on a quarter acre BOW is a lot. I do agree with you on battling mother nature...her goal is to fill in your new pond. I'm thinking ducks and excessive vegetation would be an ideal first step towards that goal. My ponds are over 40 years old, and I still deal with invasive plants, semantics aside.

Tony, you are correct in asking what the goals are for that particular pond.

Most of us here want fish and fish in the pond is the main focus. So, water quality, etc. all revolve around the fish.

Even after a year, if the pond DOES seal with the duck manure, and the ducks are removed, the nutrients in the pond will create a tremendous nutrient load, which will in turn cause a lot of plant and/or algae growth.