the pond in addition when wrapped over the sides of the erected pond it provides additional restraint to keep the walls in place the walls of the pond are fabricated using expanded foam core rigid material or other low density material which may be constructed of segments that defines the dimensions of the pond and controls the basic shape of the pond walls fastening structures are provided which hold the expanded foam core rigid material segments in relative alignment to define pond dimensions the fastening structures can include tie rods tie rod plates and tie rod fasteners in one embodiment the tie rods have threads at least at their ends they are placed through apertures defined in the expanded foam core rigid material with the threaded ends exposed tie rod plates are preferably placed over the exposed threaded ends and serve to spread the compressive load applied when the tie rod fasteners are threaded on to the threaded tie rod ends so that the load is distributed and does not crush or damage the expanded foam core rigid material the tie rods are of sufficient strength to support the tensile forces applied by the walls of the pond when it is filled with water or with its intended contents a leakproof liner comprising a sheet of pvc or other plastic liner material is used to contain the liquid generally water that is filled into the erected pond in some embodiments a layer of geo technical material can be place underneath the leakproof liner to protect it from the base fill the site where the pond will be erected is prepared by being leveled or graded if necessary so that it is approximately level and approximately flat material that is removed in.