Application of Auger Cast-in-Place (ACIP) Piles in Urban Infrastructure: A Case Study of Philadelphia’s Samuel S. Baxter Water Treatment Plant-Paper

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The paper presents the design and installation of approximately 2,100 auger cast-in-place (ACIP) piles for Clear Well Basins 3 and 4 at Philadelphia’s Samuel S. Baxter Water Treatment Plant. The two underground basins will each store five million gallons and support a critical facility supplying about 60% of the city’s drinking water.<br /><br />The site’s complex conditions included deep, variable alluvial deposits with soft cohesive layers, highly weathered schist, scattered boulders, shallow groundwater, and potential uplift forces. Construction also had to avoid vibration-related impacts to nearby operating infrastructure and the foundations of recently built basins. After evaluating shallow foundations, ground improvement, driven piles, and drilled shafts, the team selected low-vibration ACIP piles as the most practical solution.<br /><br />The 18-inch piles were designed for compression, uplift, and lateral demands, with many extending into residuum and weathered rock. Indicator piles and compression and tension load tests confirmed that the system could meet capacity requirements, with most resistance provided by side shear in the residuum and weathered rock. Test results also informed pile lengths and installation termination criteria.<br /><br />Production installation took about ten months. Key challenges included identifying the variable depth to saprolite, achieving reinforcement cover, repairing bent bars, coordinating excavation and dewatering, and managing grout delivery in cold weather. The project team addressed these through collaboration, field monitoring, design checks, and strengthened quality assurance and quality control procedures.<br /><br />The case study emphasizes that carefully selected load tests—especially tension tests where uplift is important—along with clear communication, robust inspection, and coordinated planning are essential to successful ACIP pile construction in complex urban settings.

Keywords

auger cast-in-place piles

ACIP piles

Philadelphia water treatment plant

deep foundation design

load testing

uplift resistance

weathered schist

construction quality control

groundwater conditions

urban infrastructure