So, you have your pond clear in your mind’s eye, you’ve decided on the details of how your little oasis will operate, you’ve decided whether you buy an all-in-one kit or lean on your local pond-supply guy to help you choose the best equipment to realize your vision, and you’ve ordered your liner. Now, it’s time to get serious!
Mark the Outline
Using a flexible hose, mark the proposed outline of your pond exactly where you want it to be. It’s a good idea to do a sanity check and make sure your lines of sight are where you want them and that no utility lines run close to your proposed digging site. If there are any issues, the time to adjust is now.
Once you’re satisfied, use spray paint to make the guidelines permanent. Don’t forget to mark your shelves plus any depth changes too. It’s important to keep these in mind as you’re digging so you don’t over-excavate!
Check the Plumbing
This is a great time to check your pond’s plumbing layout. Make sure there’s nothing in the way, that your pipes and electrical connections are long enough, that you’re not painting yourself into a corner. Once you’re feeling confident, it’s time to start digging.
Excavating
Whether you’re renting a small excavator or promising a barbeque to anybody who shows up with a shovel, it’s time to get to work. It’s a good idea to plan where to place soil that’s been removed so you’re not left with an unsightly hill of mud adjacent to your showpiece. If you place a good-sized tarp nearby to collect the dirt, it’ll be easier to remove without tearing up the lawn or burying it.
Be careful as you’re digging - mark clear boundaries so that your enthusiastic helpers don’t dig too far. It’s typically best to start from the outer edges and dig across to the depth of the first shelf. Then, go back and mark your outlines for the next depth change, continuing step by step until you’ve excavated the deepest point. Go slowly and carefully. After all, it’s a lot easier to widen the hole as you go than it is to try to rebuild a pond wall.
Frequently check your excavation with a spirit level to ensure your ground is even and your margin shelves aren’t sloped to dump your plants. If the pond rim is not even from side to side and end to end, the water level will be lower, and the liner will always be exposed on the higher side. This isn’t a disaster - it can be disguised with a few stones or plants, but it’s best to make necessary allowances early in the process.
As you work, remove any stones and roots, or anything else you encounter that’s not soft soil. If your plan includes plant shelves, take special care as you dig, going from the top down and outside in. The pond walls should drop vertically or slope towards the middle of the pond - never undercut the walls or shelves
A Nice Soft Blanket
One of the most critical steps in lining a pond is ensuring that the liner will continue to hold water for decades. Even a tiny rock in your shoe can cause a painful injury at the end of a long day, and your pond liner is no different. Take time to break up hard clods on the bottom of the excavation and remove anything that doesn’t crumble. Even a small rock, with hundreds of pounds of water pressing down on it, can eventually tear a liner. Once you’ve gotten everything clear, take a rake and smooth the dirt out - the bottom of the excavation should be smooth and even - no depressions or mounds. Again, the point is to distribute the water pressure evenly and make sure all portions of the liner are equally supported.
Most liner types require underlayment to satisfy warranty requirements, and EPDM is no exception. The purpose of underlayment is to cushion your liner against intrusions like uplifting rocks or the occasional invasive root. It’s basically a little extra bit of cushioning - think bubble wrap for your liner, if you will! Your underlayment should extend all the way across the floor, up the walls of your pond, and just beyond the edges of your liner so it can be securely anchored with the liner.
