From the beginning of the operation of the Olympic Pool in Tennessee there were signs of trouble. The water in the pool would not clear up, the pool liner had bubbles which appeared to grow over time, and the pool floor needed constant vacuuming. Initial thoughts by the contractor who constructed the pool was that filtration plumbing, which was installed below the pool floor, contained a significant amount of construction debris which was making its way into the pool. As the pool continued to operate, the blisters in the liner grew, which was speculated to be the result of a high groundwater table. Eventually one of these bubbles became so large that it rose above the water surface. To deflate this now very significant liner bubble, it was punctured spewing soil and water (see Figure 1).
With all the confusion and various theories on what caused this just constructed Olympic pool to fail, MEA, a UES Company, was selected to perform an independent forensic investigation.
From a borehole camera inspection it was discovered that there was a significant fracturing of the sub-floor plumbing. The fracturing was concentrated at the connector of the rise pipe and header (see Figure 2). Also from manometer survey and photographic information it was established that the pool floor and wall had settled. Normally, such pool settlement would not affect the operation of the pool but the pool floor plumbing was particularly sensitive to compressibility of the fill as the PVC floor plumbing system consisted of about a 3 ft. riser pipe connected to a header pipe (see Figure 3). The system in effect acted as a concrete slab supported by load columns (PVC risers) which were in turn supported by footings (PVC header tees). After drilling and sampling the sub-soils and performing tests in their laboratory, MEA determined that the fill installed beneath the pool floor and wall was improperly placed and caused the pipe failures. Based on this testing and analysis it was further determined that this pipe system would not have failed if the soil fill was compacted to specifications. MEA laboratory tests demonstrated under these placement conditions that the soil was not sufficiently compressible.
Although some had recommended removal and replacement of the entire pool structure, MEA determined the foundation for in-place pool walls could be repaired by pressure grouting under MEA monitoring. This resulted in a savings of several hundred thousand dollars for the owner. The floor subsoil was removed and replaced, as well as the slab and associated plumbing.