In-ground swimming pools are great on hot days when they hold water. Unfortunately, for many homeowners with older pools, they often do not, and become large, potentially dangerous holes in the ground instead of recreational areas. Repairs are costly, as is demolition, but if this is your situation and you want to make the most of it, convert your leaky pool into a pleasant garden. You can design your garden to be either level with the yard or a sunken garden with the top of the pool walls serving as handy built-in seating or shelf space for potted plants.
Review your local planning and zoning department ordinances to ensure that your project is legally permissible, and get any necessary building or demolition permits before beginning work.
Hire an engineer or qualified inspector to check your pool for soundness and follow her recommendations regarding the pool.
Hire a demolition contractor to remove the pool if that is the recommended option. He will bring in heavy equipment to break apart the walls and floor of the pool, then use the debris as the base fill for the resulting hole.
Obtain coarse fill dirt, which may contain chunks of masonry construction debris or large stones, and spread a layer up to three-fourths the total depth of the pool over its bottom. Adjust the depth of this coarse fill as needed for your planting goals. For example, the deep roots of trees and shrubs benefit from a greater depth of finer-quality soil atop the coarse fill dirt while flowers and grasses with their shallower roots will need only a foot or two of good soil.
Use gravel to fill in any irregularities or holes through out the fill dirt, including covering large rocks and other debris to create a smooth, level surface on that layer.
Tamp down the gravel and fill dirt with a mechanical tamper to make sure that it is well-compacted and firm. It should not shift or depress when walked on.
Add 2 or 3 feet of good soil over the layer of fill and gravel and firm it as before, then follow with rich topsoil to the required finish level, raking it smooth.
Water the surface of the soil until puddles form, and then let it stand for a few days to drain and settle before planting your garden according to whatever design you prefer.
Follow the process above, but stop short of filling the pool, perhaps 3 or 4 feet below the surface of the walls, to create a sunken garden, if inspection shows the walls are sound. Use existing pool steps to access the garden. This is a nice option in a particularly windy area as it provides a wind barrier for tender plants. It can also add interesting depth to an otherwise flat and featureless yard. If you plan the garden ahead of time, you can shape hills and valleys or even leave space for a recirculating pool or fish pond in your new garden as you fill it, saving yourself the trouble of excavating those areas later. Construction and demolition firms routinely look for places to haul dirt from their excavations so you may get all you need free of charge merely by asking.
Depending upon the laws and ordinances where you live, you may have to remove underground plumbing and electrical portions of in-ground pools, as well as steel reinforcement and, in some cases, the concrete itself. Check your area's requirements first to save yourself the time and expense of removing your newly planted garden to correct the mistake.