Geotechnical and Geo-structural feasibility analysis and design
Brierley-designed secant pile wall system with tie backs enabled construction in challenging ground conditions
Secant piles served as temporary excavation support and designed to function as the permanent foundation and exterior walls of the new Backwash Tank.
Plant location adjoins flood-prone Susquehanna River
During construction of a prior upgrade project, the Binghamton-Johnson City Joint Sewage Treatment Plant suffered a catastrophic failure of one section of the plant, resulting in a sewage release to the adjoining Susquehanna River. Several months afterword, historic river flooding inundated much of the property which exacerbated the situation.
Brierley Associates was retained to provide geotechnical and geo-structural feasibility analysis and design of the secant pile wall system, slab anchors, and related support elements for the construction of an underground backwash tank. The 40-ft deep by 96-ft wide and 192-ft long excavation was supported by secant piles with a bottom elevation that ranged from about 28- to 39-ft below the local groundwater table.
Brierley designed the 5-ft diameter secant piles which extended 36- to 45-ft below the surrounding ground surface. Our design allowed for the secant piles to serve as the temporary excavation support while functioning as the foundation and exterior walls of the Backwash Tank. During construction, the internal bracing to support the secant pile wall consisted of reinforced concrete wale beams and struts that were founded on caissons installed within the excavation footprint. The internal bracing and caissons remained in place to function as a permanent support element. Prior to the construction of the secant pile wall, demolition and removal of existing structures, grade beams, and foundation elements in the area of the backwash tank location were completed. This required, localized deep excavations to remove piles that would have obstructed secant pile wall installation.
Due depth of the tank below local groundwater and proximity of the Susquehanna River, Backwash Tank slab uplift and stability were concerns. This was overcome by the installation and tensioning of over 130,32-ft long, epoxy coated # 14 Dywidag anchors encapsulated in corrugated HDPE.
Brierley provided construction phase engineering services, full-time resident engineering and related support services during secant pile and anchor installation.