OasisLMS

Abstract: This paper presents a case study of implementation of auger cast-in-place (ACIP) piles to support the Clear Well Basins (CWB) 3 and 4 at the Philadelphia Water Department’ s (PWD) Samuel S. Baxter Water Treatment Plant. Situated along the Delaware River near Philadelphia’ s northeast boundary, the Baxter Treatment Plant has supplied the city’ s drinking water since the early 1900s. Increasingly stringent water treatment standards, aging infrastructure, and Philadelphia’ s recent population growth has necessitated upgrades to the Baxter Treatment Plan. CWB 3 & 4 consists of two 5-million-gallon side-by-side, below ground, cast-in-place concrete basins to meet the rising water demand in the Philadelphia area. Geotechnical investigations of the site revealed significant challenges, including high groundwater table, presence of alluvial deposits 30 to 50 feet deep, variable depths and weathering of the underlying Wissahickon formation, tidal fluctuations in the Delaware River, buoyancy uplift forces, and potential impacts on adjacent CWB 1 & 2 foundation elements. These complexities made traditional deep foundations (e.g. drilled shafts, driven piles, micropiles, etc.) not feasible. Ultimately, the design team selected ACIP piles based on past experience with similar subsurface conditions and suitability of ACIP piles for their high load capacities, ease of constructability and cost-effectiveness. The final design for CWB’ s 3 and 4 consists of approximately 2, 100 ACIP piles ranging from 30 to 65 feet deep and socketed into weathered Wissahickon schist. The case study examines the advantages of ACIP piles in complex geotechnical conditions, focusing on pile design, load testing program, construction monitoring, and the challenges encountered during their installation. It also highlights importance of robust QA/QC procedures, effective stakeholder management, and comprehensive planning and coordination in successfully delivering a critical infrastructure upgrade.

Mr. Michael Whelan; Mr. ABHIJIT SHETH

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