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

PPT Presentation

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The Philadelphia Water Department replaced the approximately 120-year-old clear well basin at the Samuel S. Baxter Water Treatment Plant with Clear Well Basins 3 and 4, a critical facility serving up to 100% of the city’s water demand. The site presented challenging conditions, including variable alluvial soils, a weak and unevenly distributed cohesive layer, shallow groundwater, weathered rock, and nearby operating structures sensitive to vibration.<br /><br />Auger cast-in-place (ACIP) piles were selected to support the basins’ dynamic loads and resist uplift while limiting vibration and noise. The final design used 18-inch-diameter, grout-filled piles with reinforcing steel. Indicator piles and compression and tension load tests verified performance and informed installation procedures. Testing showed low displacement under design and elevated loads, with resistance coming primarily from side shear in residuum and partially weathered rock.<br /><br />Pile termination criteria were adjusted to account for changing rock elevations and subsurface conditions. Construction teams also addressed discrepancies in field and reference logs, insufficient grout cover, bent reinforcing bars, and the need to expose and trim piles at the influent and effluent houses. Dedicated on-site quality assurance and coordination among the owner, designers, contractor, and testing agencies helped resolve these issues.<br /><br />From October 2024 through August 2025, crews installed 2,104 production piles totaling approximately 112,500 linear feet, averaging about 10 piles per day. The project demonstrated that ACIP piles can provide reliable capacity in complex geology with minimal vibration. The presenters emphasized the value of indicator and uplift testing, robust quality control, and rapid communication in delivering specialty foundations for urban infrastructure.

Keywords

Philadelphia Water Department

Clear Well Basin

Samuel S. Baxter Water Treatment Plant

ACIP piles

auger cast-in-place piles

dynamic loads

uplift resistance

load testing

alluvial soils

specialty foundations