Foundation construction within wastewater-treatment plant

The entire foundation design and construction histories of a project built inside an existing wastewater-treatment plant are described. The foundation type decision process, based on the subsurface conditions, the existing structure’s performance, and the proposed facility’s constraints are outlined. In addition, the foundation construction histories, including foundation specifications, construction dewatering and monitoring, pile-load-test results and production pile driving records, are summarized. Weak soils existed to significant depths over the entire site as did a high ground-water table. Since the elevations of the bases of the structures varied significantly, it was also cost effective to vary foundation type depending upon the estimated load-carrying capacity of the soil at the base of the proposed foundations. Consideration also had to be given to the possibility of detrimental total and differential settlements as a result of dewatering as well as differences in foundation type between existing and proposed structures. This project demonstrated that a properly designed and adequately executed foundation construction program can effectively eliminate the need for expensive underpinning of nearby existing facilities. And, pile load test is a reliable tool to establish the driving criteria, to confirm the design assumptions, and to economize the required pile length.