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Scope of Work:
¨ Site preparation at this urban village site included upgrades to the existing security fence, extensive erosion and sedimentation controls, and relocation of the lower parking lot to a new temporary lot.
¨ Prior to the in-situ solidification (ISS) phase of the project at the Hudson Vista Lower Terrace, the top 3’ of impacted soil and asphalt was removed and shipped the material offsite for disposal. ‘Clean’ asphalt was stripped first and direct loaded for recycling. Excavation of the remaining overburden was performed using traditional excavation methods and standards.
¨ The ISS sediment mixing encompassed approximately 2,500 CY and was performed to an average depth of 15’ below grade where a natural clay formation provided vertical containment.
¨ A total of 202 borings were completed using ISS auger methods with a Delmag RH-18 foundation drill and 6-CY grout batch plant.
¨ Two auger sizes were used; 5’ auger (82 columns) and 8’ auger (120 columns).
¨ The ISS design mixture was a 7.5% Portland cement and 0.5% Wyoming bentonite clay, with performance requirements of 1x10-6 permeability and 50 psi compressive strength.
¨ Completion of the Lower Terrace included the placement of additional fill on top of the stabilized waste to achieve the desired subgrade for the final asphalt cap. Three inches of asphalt was installed along with parking curbs and final striping.
¨ The second (and larger) phase of the project required the complete excavation and disposal of MGP impacted soil and structures on the Upper Terrace. Due to the proximity to the Village of Nyack, the majority of the excavation was performed under a temporary fabric structure (TFS). The selected TFS was a 132’ x 148’ structure from Universal Fabrics. TFS erection also required the construction of a 15’ temporary retaining wall in order to support one corner of the structure. Ventilation units included three TIGG NB-20 air treatment systems.
¨ Excavation and structural demolition yielded 25,000 tons of coal tar impacted soil and 2,000 tons of demolition debris. Most of the waste materials were shipped to ESMI’s New Jersey facility for thermal treatment via LTTD.
¨ Upon completion of the excavation, the TFS was removed and the site was restored with minimal backfill and crushed stone (largely for slope stability) as necessary to convert the Upper Terrace into a staging area for future construction activity.
¨ The community protection requirements included an extremely strict set of controls for noise generation, odor suppression, and traffic control for waste hauling and construction traffic. It should be noted that there were no odor complaints throughout the entire project and the Village was extremely pleased with the traffic management program.