Economy and Design of Augered Cast-In-Place Piles at the Fargo WTP

The Fargo water treatment plant improvement project is a $104 million plant addition located in Fargo, ND. The original foundation design for the addition consisted of 346 each 42-in. diameter drilled piers; similar to the existing plant foundations. A value engineering (VE) alternate foundation system was proposed that consisted of a 1-for-1 replacement of the drilled piers with auger cast-in place (ACIP) piles of equivalent capacity. The VE alternate proposal saved approximately $4 million and 15 weeks in the construction schedule. The ACIP pile VE alternate was ultimately selected for the project. A pile load testing program was undertaken to verify design assumptions and optimize the design of the piles by determining the frictional resistance being developed along the length of the test pile within each subsurface layer. The load testing program consisted of four reaction piles, and one sacrificial compression load test pile that was tested to a maximum test load of 704 kips. The pile load test was successful in verifying design assumptions, and verifying that the proposed ACIP pile was an appropriate deep foundation element for the project.