King of Prussia, PA – The fitness center project consisted of a 51,658 sf, 3-story main building with an indoor pool and a 66,491 sf outdoor area with a lap pool, recreation pool, and water slide with a pool house. Despite the relatively shallow bedrock disclosed by the subsurface exploration, some isolated instances of sinkhole activity were documented, as is typical for this geologic region. Considering the uncommonly large column foundation sizes and loads (up to 16 ft x 16 ft and 1,200 kip), and the clients concern of the pools leaking, a sinkhole mitigation program was designed by the project geotechnical engineer.
Initial compaction grouting bids received by the client proved to be significantly out of the project budget. Deep foundation alternatives were proving more competitive. However, the client’s preference was to use compaction grouting due to its advantages with scheduling and permitting. CGS was able to work with the developer to value engineer a compaction grouting program to fit the budget and schedule. By using a third party geotechnical engineer to develop and oversee the grouting program, CGS was able to provide a lump sum contract essentially “buying” the entire compaction grouting package (engineering/design, performance, inspection, and certification), all within the project budget.
The final grouting program consisted of 1 to 9 primary grout injection locations per column based on the size of the footing (about 8 ft on-center), and primary grout injection locations at 10 and 15 ft on-center along shear wall and continuous wall foundations, respectively, for the main building. A 15 ft on-center split spacing grid pattern for both the indoor pool and outdoor pool area (2 pools and water slide) were also part of the program. This final grouting program reduced the number of grout injection locations from 822 original primary locations to 466. Correspondingly, the project schedule and budget were reduced by over 50% from the initial bid.
CGS mobilized on-time to complete the grouting program ahead of schedule by 2 days. When completed, the final grouting program consisted of 471 total grout injection locations, 10,777 lf of drilling, and 506 cy of grout injection. Due to the lump sum contract provided by CGS, there were no budget overruns typically associated with unit rate grouting projects nor were there change orders for out of scope work.