Down to Earth

Preparing the Site:  Clearing Trees to Trenches

By Mike Otto

Not all sites have trees that need to be removed—and not all trees need to be removed from each site. This is a decision that needs to be made thoughtfully. Once a tree is removed, it cannot be replaced. This is part of the reason it’s important to mark the water line. A key part of planning to build a pond or lake is to set flags at the proposed water line. Trees close to water’s edge may or may not need to be removed. Leave those until later. Trees can always be knocked to the ground once you see the final shore line.

Heavy on the words, “final shore line”. Expect the eventual shoreline to be slightly different elevation than the first flag line…up or down.

Flagging the water line allows you to visualize the horizontal plane that will be your lake. Crucial decisions are made when the water line is flagged. Trees are part of those decisions.

All trees where the dam is going to be built; the emergency spillway, and the borrow area must be removed completely, including roots. The dam must be set on clean ground; no stumps or tree limbs or roots. Hand labor is often required at this stage of the project. Cleaning up the scraped site is easier and cheaper when picked up by hand. That’s how I started, as a stick-picker. No sticks, roots, or limbs…nothing on the dam site except dirt. Rake, pick up, pile, burn. Typically, we collect this organic stuff, place in small piles and burn it. This is a good, quick, efficient technique to get rid of debris. Most of the time, excess timber is piled and burned, but not inside the dam site work area. Some of the appropriate trees may be saved for placement inside the lake for fish structure after the dam is completed.

As your process happens, be sure to understand, you are in charge. It’s your lake. Caveat emptor.

Take a deep breath, look things over. We are well past preliminary planning stages but changes will continue to be made. Be light on your feet, so to speak. By now, there has been money spent, money that will actually save dollars in the next couple of phases. Your job is to see the progress and make choices. As the dam is built, unknowns will be uncovered. Types of dirt, depths, ridges, humps, gravel veins, sand…you are in charge.

The budget, site preparation, topsoil, clearing, core trench, where the dirt to build the dam will come from, and what happens above the water is all next.

Preplanning has been a key part of your success. As the equipment does what it does, you still have decisions to make.

While this stuff may seem a bit overwhelming, it’s not. It’s part of the logical process.

            The price of building a lake varies depending on location and the specific site. For people that live in Pennsylvania the cost will be a lot higher than where I live in Texas. Many more regulations and permits. Not just for the property owner but also the contractor. Politics come into play.

            In some cases, a quarter to half of the expense is before any equipment has hit the ground…that’s part of the politics of your state, and how they interpret federal, state, and local laws.

            Once the dozer has unloaded, the clock is ticking. So, let’s get this as close as possible.

Site preparation; Getting heavy equipment into the property, setting up a staging area to park equipment and doing final surveying will depend on size of project and that preparation cost is often rolled over into the dirt work itself.

Then, there’s removing topsoil; and the plan to use it later.

Topsoil is stockpiled for use when the dam is completed. Just as important is the fact that fertile soil (topsoil) left inside the lake basin will make aquatic vegetation a lot harder to deal with inside your management strategy. Get topsoil out of the lake, as much as is feasible. It can be saved and used on the backside slope of the dam if there is room…or other places around your property. Tip: Staging topsoil piles close to the dam site is best, but may be out of the way. Removing topsoil is not wasted time or money, anything that can be done to eliminate maintenance problems later will pay. Yearly costs of aquatic vegetation control add up.

            Now is a good time to really look things over. If part of your plan is to have a place to stay when you are at the lake, stand on the building site and look it over. Compare to your water line. Something may need to be moved—the house or the water line—or nothing. Where is the dock going to be? This could change a little but by now we want to have a general idea. Placement of a boat ramp, swimming area, how far from the water will the house be, what kind of yard and grade, most of the time this is an area that is built to be mowed.

            Once upon a time we built a seven-acre lake on a beautiful piece of property.

            Lots of planning and decisions happened before we moved any dirt. House location, with beach area, ramp, walking path, tree placement, and a couple of islands were planned. Lake was completed, with lots of native rock retaining walls around the house site and a gravel road across the dam, led to a big parking area and a circle drive.

Equipment moved off site, on to next job. A year later with the lake full I got permission to come and take a look. The road to the dam came from the back side and the lake was not visible until the top of the dam was reached. As soon as everything came into view it was clear they had moved the location of the house, not just a few feet but to the other side of the lake. A beautiful location on a slightly higher hill, with the setting sun facing the back of the house, not the front. No doubt this was a better location, mainly because the owner liked it better. There was a lot of expense the first time around…and also the second time. A good lesson for me to make sure the land owner has as much information as possible—and time to think things over.

With the site cleared and prepped, it’s time to dig the core trench, also called a keyway. Here’s another important point to understand. All dams leak. The contractor’s job is to minimize seepage. The core is the work done below ground level to ensure water will not escape under the dam. Often this is only a few feet but could be much more and we want to know how deep before we get started. A general rule is the larger the drainage area the bigger the core work will be.

            A project that has twenty-five acres of drainage may not have a lot of underground work, but a thousand acres of drainage with a running creek will require lots of work.

            We built a dam on a watershed drainage that covered a wide area with a creek that ran water most of the time. The engineer had ten test holes dug. Even with this much information gathering there was an original creek bed that was missed. During excavation this lower creek bed was discovered. It had to be excavated and refilled with material that would stop underground seepage.

There are many stories about dams not started properly. Some by accident, a missed water table, a tiny sand layer not found, and even spots where creeks were rerouted decades ago. These are mistakes that will cause problems and be very expensive to fix.

All the more reason for thorough due diligence and test holes…and communication.

            The core trench is backfilled with the very best material available—think clay.

            If the job is big enough and has an engineer with a set of specifications, make sure the work is done properly.  It does not cost much to have a test laboratory inspect the soils. They will give the dirt guy results instantly.

            On smaller jobs, the dozer man will be his own inspector. He will only use good material, making sure it is clean and properly compacted.

            Bulldozers have been used since the beginning of time for mixing and compacting dirt and have done a great job. Today, it is still a primary tool, but sheepsfoot rollers, wheel tractors, and heavy dump trucks all help in the processing and packing of the dirt.

            While we’re still in the planning phase, we still want to focus on the water line. That’s your first proposed elevation where the lake is full to the primary spillway. Next, judge the water depth all over the lake basin and make sure you have very little shallow water and the slopes all around the lake will be good. As this happens, the dirt man is figuring out the best place to get the dirt to build your dam.

            General information; there are the three mortal sins of shallow water.

            One: It will allow aquatic vegetation to grow more easily—that will be a never-ending expense. This can be eliminated to a certain extent now.

            Two: Shallow water will evaporate faster than deep water. An acre of water one foot deep will be gone before one foot of water off the top of a deep pond will be.

            Three: The surface will shrink to half its size, if the water level drops a couple of feet.

            Get rid of shallow water—either by moving the dirt to the dam or maybe doing a cut and fill, balancing the dirt in the lake. Heck, build a peninsula or a point.

            Planning these things is significant. When the contractor cranks up the machine and starts taking out trees, clearing the dam site, setting up his staging site and digging the core trench, that whole ecosystem changes…and changes for decades beyond how it is now.

            Be sure to think through it and ask for advice. It’s worth the effort.