The Core of Building Your Lake


Down to Earth

The Core of Building Your Lake

By Mike Otto


Okay, you’ve had several weeks off reading this stuff, so let’s get back to work...’er having fun.

We have methodically worked our way through the process of building your lake. Here’s a recap.

The Plan—this is all yours and anybody that is part of the decision-making process—usually the bride. This critical exercise with maps entailed watershed, dirt, siting the dam, figuring out who will build it and trying to visualize what your new pond will actually look like.

Things to think about:

How much do you personally want to be involved in the building process? When the lake is full how much time do you want to spend managing the water, mowing the grass, and doing important maintenance? Is this a getaway or a place to have family and friends?

Very little money was spent so far—mainly time looking at maps, some time on the web site, other hours on YouTube looking at videos, other pictures and asking questions.

Hopefully you’ve been able to spend time on your land, walking the site, thinking this through and driving around the countryside looking for ideas to make your dream come true.

We learned maps are our friend, cheap, and easy to get to.

By the way, maps will be used all the way to the end of the project, from planning fish habitat, road placement, house site, swimming areas and any other amenities you can dream up. The value of experienced help cannot be discounted. Other people’s input, lake builders, engineers, pond design consultants, and dirt contractors will offer lots of good advice that will make the experience more enjoyable, go more smoothly and less costly.

The more you know, the better decisions. Understand from the beginning that you don’t know what you don’t know. Learn it.

There are rules. Some are common sense, like keeping the water on your property, it must come and go in the same place as it always has. Some rules are legal; we are living in time when it may be necessary to get permission to build something on our property, so a conversation with an engineer may be wise.

While maps are crucial, all that good information must be doubled-checked on the ground.

Trees are a big part of the planning process. Which to leave, which to take? Do they have value beyond intrinsic?

The way Mother Nature has carved out the land will help make decisions.

A site that has rocks may be a blessing if we use them properly. They could be a curse as well. Rocks are good for riprap, but not so good in a dam.

Information gathered walking around the site, finally yields to action. Next is preliminary staking. Stake the dam site and spillway location first. It could change but it’s a good start.

Stake the shoreline where the water will be when the lake is full. Lots of important decisions are made when we know this. Decisions above and below the water are important. There may be things that must be removed, such as old trash piles and underground abandoned pipelines.

Exploration of the site includes the test holes. Gotta have the right kind of dirt to build a dam. Test holes help tell what needs to be done below ground.

A contractor will be involved now and budget will start to come into focus. Next you have a final layout, spillway location, pipe-size (if needed) all completed. You may need adjustments but not much.

Next up:  Site preparation, topsoil removal, clearing, foundation work, and core trench.


Phase Two:

Now, the real work gets started. Dirt is moving, the site is cleared, the core is being worked. Placement and depth of the core was determined when test holes where dug. The material that is coming out of the trench may be reused in the back side of the dam or in some cases it will have to be removed from the site all together.

If the dirt from the core trench has a layer of sand but the rest of the material is good clay, it can be used in the backside of the dam, but if it is a muddy, sandy, gravely mix it will not be suitable to be used anywhere in the dam.

Once the site is cleared, the core trench is finished, it’s time to start going up. Truly, the dam is being built now from below the ground, up

Material going back into the trench will be the best clay available. It could be inside the shore line but it may have to be moved from someplace else on the property. Find good clay.

This may be the starting of dam construction, but remember, your pond or lake has several jobs. The dam’s job is to impound water and release excess water in an orderly fashion.

This may seem a little like double talk but it is not. The dam is where dirt is placed and its job is to hold water back with measured slopes and all the dirt is compacted. A slope that is measured three to one (3-1) the contractor can operate equipment safely, also smooth and grade so topsoil can be replaced and grass planted. If the plan is to mow the slopes of a dam the grade should be extended to a four to one (4-1).

The dirt that is put in the dam will also be used to have a road across the top of the dam. Top width should be a minimum of ten feet wide and can easily be extended to twenty if the dam is to be used for a road.

Behind that dam is a living, breathing lake. Design the best habitat possible. Now is the time for that. Eliminate shallow water unless you specifically have a purpose for it. When the dirt is moved out of the hole, we are carving a fishing lake, eliminating shallow water, creating swimming areas, cutting benches, and trenches. It is like sculpting; “everything is removed that does not look like a fishing lake.”                        

Dirt placed in the core trench can be pushed with a dozer, loaded in a dump truck and moved, or hauled with a scraper. The book says six-inches is the optimal depth for lifts of dirt layered in the trench and then compacted.

Compacted dirt is defined as all the particles squished together as much as possible. This is done with weight and moisture. If the lift layer is more than six-inches deep it cannot be compacted, if the proper moisture is not in place, it cannot be compacted.

There is nothing magical about compaction but it has to be done properly and carefully. For bigger projects, it is wise to have a soil testing laboratory come to the site and periodically test material as it is placed in the dam.

A competent, experienced dirt guy may feel confident in his work. If that is the case no inspection is necessary-but all of us like a good professional to check our work. It takes the pressure off, and lets us sleep better. If you are confident in that experienced dirt guy, all the better.

With the core trench filled up to ground level, a similar process keeps dirt moving and compacted to the top of the dam.

No site has all good material. Don’t skip by that sentence. It’s important to understand. The best material is placed in the center of the dam and will continue in the same area as the core, all the way to the top. The next best material will be placed on the front side of the core and the least desirable dirt will go behind the core on the back slope.

Essentially, we are building an earthen wall with the least porous, best compactable dirt through the middle of the dam. Lesser dirt can go on the slopes.

For compaction, moisture is critical. Water, if needed, can be added with a water truck, sprinkler from a water pump, or waiting for rain may be necessary. The water is a lubricant that helps the particles slip together and bind.

As far as the weight to do proper compaction; a sheep’s foot roller, a dump truck full of dirt, a full scraper, or maybe a wheel loader is good for the job. All of them will work as long as there is proper moisture. The book says traveling over the area eight times will ensure that proper compaction is reached.

The secondary (earthen) spillway will also be built as the dam is being constructed, usually toward the end of the project. Most of the time this is carved, smoothed, and leveled so topsoil can be spread and grass planted.

Next article we will go over pipe, spillway, and a drain pipe with a valve. These are often options you can use—and especially what not to use—and the proper way to install the pipe. Also, we’ll cover some of the finishing touches on the dam, spillway, and what to do where the water goes back into the original creek channel downstream.

There’s a lot of work yet to do. The finishing touches are the most fun, and will make the lake easier to use and much more enjoyable.

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