Trampolines are increasingly popular backyard toys and can be fun for the entire family. While giving everyone a great workout, trampolines can also be potentially dangerous if jumpers fall off the edge and hit the ground. You can lower your trampoline and install a ground-level trampoline that will be flush with the ground to help prevent injury. Although placing them is a little more work, ground-level trampolines blend into your backyard effortlessly and greatly reduce the possibility of injury due to fall.
Measure the size of your trampoline before you start to dig. Be sure to measure the height of your trampoline as well, so you know how deep you will have to make your hole. The trampoline should not be perfectly flush with the ground. It needs airflow below if it is to be bouncy, so plan on its being above ground about 1 to 2 inches.
Decide on where to place the trampoline in your yard. Make sure the ground is level and there are no trees or other obstacles nearby. Dig the hole to your measurements.
Create a retaining wall. You can purchase interlocking walls specifically designed for lowering your trampoline, or you can make a retaining wall out of concrete blocks or corrugated metal sheets. Interlocking walls are easier, but more expensive. If you decide to use blocks and mortar, allow 24 hours for set blocks to dry.
Backfill the hole with gravel and dirt. This will reinforce the retaining wall and help with any drainage issues. However, do not completely fill the hole under the trampoline --- leave about 3 feet empty for jumping space.
Put the trampoline in the hole. You will probably need several people to complete this task. Make sure the trampoline fits securely, and put up any enclosures you wish to use for added protection.