Hi! This past May 2020 we contracted to have the liner replaced on our 18x25 inground pool and add width sized steps. The need to remove a section of concrete apron about 1 1/2 ft x 2o ft to get to the end of the steel pool shell to remove it. They dug down and removed most of the pea gravel base and foundation under the entire shallow end of the concrete apron which is 3 1/2 ft x 20 ft. The concrete was quite thick, 6 in. By removing the pea gravel, the entire apron (3 1/2 x 20) collapsed causing a major difficulty in keeping the surrounding gravel in place which was also the base for the connecting patio. Sheet pilings were used, which seems to have worked. What should they have done to prevent this from happening? The renovation has lasted all summer and fall.