The Excavation process is the ‘ground breaking’ step. First you mark off your perimeter with paint marks. From there you will need to start excavating the dirt. Depending on the size of your Koi pond, generally a backhoe, bobcat, or shovel(s) are used. If you are going to rent machinery, be aware that the more time it takes, the more money it will cost.
If you are hiring an excavation company to do your work for you, don’t be afraid of big companies. Although the smaller, more localized companies are great, what it really comes down to is experience. Ask as many questions as possible. See how long the company has been in business, how large the company is, and how many ponds they have dug. Search for reviews online at places like Yelp.
One potential problem that is frequently overlooked is access to your pond. If you are bringing in heavy machinery, you always want a clear path from the road. Many times fences, trees, lawn ornaments, etc. can obstruct the path to your desired pond location.
It is crucial during the excavation process to have all proper draining and elevations in place. The Koi pond elevation is crucial to the excavation process, as it gives proper drainage from the top of your pond. This is more common when building pools, but if you are planning to have concrete around your pond, this deems equally as important. The rule of thumb is 1/4” slop for every foot around your pond. You want to make sure that the elevation of your pond is in sync with any surrounding objects such as a deck, or patio.
One other major consideration is where your lights are going to be. It becomes extremely difficult to add spaces for lights after the excavation phase. The first time that I built a Koi pond I made the mistake of not digging out holes for lighting. When it came to the steel phase I was asked where might lighting was going to go. I had to quickly dig out holes and add electrical which held up the steel process.
When digging, you want to dig an extra 9” to account for 6 inches for the Koi pond shell, and 3 inches for the water level (water will be 3” below the top of the pool). When you begin digging, you may want to consider keeping some of the dirt for landscaping needs when the Koi pond is completed. This dirt can come in handy if building a waterfall, or for fill for rocks, etc.
One other major consideration is a backwash pit. If you need to drain your Koi pond, you want to make sure that you have a place to drain the water. This is important to plan before digging, as it may be hard to access the area for the backwash pit if you have already dug out your Koi pond. A backwash pit is generally a trench approx. 4’ x 10’ that’s between 1/2’ to 3’ deep. Generally they are filled with river rock or similar filler. When you drain your Koi pond, the water will drain into the backwash pit, where it will evaporate and be absorbed by the earth. Most people choose to position the backwash pit next to their Koi pond equipment (pumps, etc.).
You will want to put wooden stakes 6” around the initial layout lines that are drawn inside of the perimeter. This is to account for the Koi pond shell. The stakes are placed in to hold up the forms (generally flexible pegboard material) of the Koi pond. After placing the stakes, it is a good idea to measure the distance between stakes, and mark them. You want to do this because generally the paint is destroyed during the excavation process, and you will better know how to dig the Koi pond. If you are planning on having any sort of waterfall or rock features, you will want to lay stakes at the layout lines. You will not need to pour fill in these areas, as you won’t want to lay rocks on the fill.
When digging, the first couple of feet are generally the toughest. This is because home builders are required to compact the top soil and grade it per code. Do not get discouraged! Once you get through the hard surface layer, the digging is a piece of cake.
The excavation process on average takes 2-3 days with a professional crew. After digging the majority of the dirt, I suggest taking a hand shovel for all of the trimming. It is best to be as precise as possible. As you can see in the picture, we have dug our around the waterfall approx. 8” and marked off the perimeter with forms.
If you choose to use a bobcat, or any other vehicle that needs to drive into the Koi pond, you will need to use a ramp. Once the work is completed, you will have to manually dig out the area with a shovel. I suggest using sandbags to fill in the wall, as they will keep shape and are sturdy.
Once you have completed all digging and form work, you are ready for plumbing!