CASE HISTORY: INNOVATIVE LOAD TEST PROGRAM OPTIMIZES PILE CAPACITY IN CHALLENGING GROUND CONDITIONS Emad Farouz, P.E., CH2M HILL, Chantilly, VA, USA Francis A. Abreu Sr., P.E., CH2M HILL, Chantilly, VA, USA This paper presents a case history of a successful construction-phase pile load test program that optimized the pile design in challenging ground conditions at the Great Neck Wastewater Treatment Plant in the Town of North Hempstead in Nassau County, New York. The improvements and expansion of the wastewater treatment plant included the construction of several new structures to comply with new stringent nitrogen discharge requirements and new design flow. The challenging ground conditions included up to 20-ft thick organic deposits with weight of hammer blow counts and up to 14 percent organic content and tidal ground water that was near the ground surface. The foundation design evaluated various deep foundation alternatives and selected driven closed-ended pipe piles then filled with concrete as the most suitable foundation. The selection process included considerations of cost, risk, vibrations, noise, and schedule. The contract documents utilized an innovative approach of performing an optimization load test program that was implemented during construction to optimize pile lengths and reduce potential vibration and construction schedule. This paper discusses the details of the successful load test program including static testing, dynamic testing, and the innovative contracting approach utilized to implement the construction phase load test program. It also discusses the successful development and implementation of driving criteria for production piles and construction challenges. The successful load test program resulted in savings of several hundred thousand dollars, optimized schedule, and lower environmental impacts. SITE AND PROJECT DESCRIPTION The Great Neck Water Pollution Control District (GNWPCD), located in the Town of North Hempstead in Nassau, New York, owns and operates a municipal wastewater treatment plant (WWTP) that discharges treated effluent through an outfall to Manhasset Bay, which is a tributary of the Long Island Sound. The site is located west of Manhasset Bay and is surrounded on three sides by local roads, and commercial, industrial, and recreational properties. The site has a gentle slope ranging from elevation +20 to +7 from west to east, respectively, based on the Nassau County Datum. To comply with new nitrogen discharge requirements and new design flows, the GNWPCD contracted CH2M HILL, Inc. and William F. Cosulich Associates as a Joint- Venture (JV) to design and provide services during construction of eight new advanced nitrogen removal facilities. GEOLOGIC SETTING AND SUBSURFACE CONDITIONS The Great Neck peninsula is underlain by unconsolidated glacial deposits consisting of gravel, sand, silt, and clay, and coastal-plain deposits. Geologic documents report that these deposits are underlain by biotite-garnet-schist rock at depths greater than 400 feet below ground surface. Historical subsurface information was evaluated along with a subsurface investigation program conducted by CH2M HILL in 2009 to characterize the subsurface conditions and develop soil properties. Exploratory borings performed during the investigation extended to depths ranging from 82 to 102 feet below ground surface using mud rotary drilling techniques. Standard Penetration Tests were performed during the field investigation and samples obtained for laboratory testing.
