Abstract:
Haley & Aldrich has been involved for over ten years with the remediation of a former manufactured gas plant (MGP) site. The site had an existing, active natural gas distribution center operating during the majority of this remediation period, requiring phased environmental remediation strategies that were protective of the existing infrastructure. The first phase of remediation efforts involved excavation and removal, requiring a tied-back soldier pile and lagging system supporting approximately 40 ft of soil. Subsequent remediation phases used a combination of excavation and in-situ stabilization (ISS). While typically consisting of soldier pile and lagging, excavation phases posed several interesting design scenarios: e.g., because ISS (with typically a 6 ft or larger diameter auger) would be performed once the bottom of excavation was reached, a dual wale was designed to support the soldier piles during the temporary condition wherein the soils in the passive zone would be liquefied; former masonry gas holder walls were analyzed and used to support excavations as deep as 24 ft; solidified ISS columns were used in other areas; previously installed soldier pile and lagging systems were re-used (on the “reverse†side) years after backfilling from their original use. This presentation will provide an overview of the timeline of excavation and remediation phasing for approximately 10 acres of property and a discussion of the various excavation support systems used.Â