Excavation Support for the Remediation of a Former Manufactured Gas Plant Site-PPT Presentation

PPT Presentation

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The presentation describes excavation support for remediation of a 10-acre former manufactured gas plant that had operated since 1875 and remained an active natural gas facility during cleanup. Remediation began in 2010 and was nearing completion.<br /><br />Early work involved excavations up to 40 feet deep, supported by 55-foot soldier piles and lagging with two levels of tiebacks. Later phases combined surface-soil excavation and disposal with in-situ solidification (ISS), using large-diameter augers. Excavations were supported through sloping, soldier pile and lagging, ISS treated as a gravity retaining wall, and reuse of support systems between phases. Designs also accounted for temporary reductions in passive resistance and site flood conditions.<br /><br />Existing infrastructure and historical structures created installation challenges, particularly where the extent of a former masonry gas holder was uncertain. Historical aerial images, plans, and photographs helped locate and assess it; test pits and excavation confirmed the walls were in good condition. They were then used to support internal excavations up to 24 feet deep.<br /><br />ISS strength varied substantially, so engineers evaluated it as a retaining structure for sliding, overturning, shear, and moment capacity. Excavation beside the ISS was limited to 12 feet.<br /><br />Key lessons were to investigate historical records thoroughly, coordinate closely in the field around active utilities and structures, and use phased remediation to maintain plant operations and reuse excavation-support systems. Former structures could present hazards but also provide useful support.

Keywords

excavation support

remediation

manufactured gas plant

soldier piles

tiebacks

in-situ solidification

historical structures

retaining wall

soil excavation

utility coordination