ConEd contracted with Conti Environmental & Infrastructure, Inc., the performance of remedial actions at a former Manufactured Gas Plant (MGP) site. Remedial action required excavation of contaminated soil impacted by MGP operations, which extended to a depth up to 22 feet. The presence of retail stores immediately adjacent to the excavation required the use of an support of excavation (SOE) system and monitoring. Distinct Engineering Solutions, Inc. (DESI) was retained by Conti to perform subsurface soil and groundwater investigation, identify contaminants, and perform in-situ waste characterization and classification for disposal. DESI developed an Excavation Management Plan that identified methods to directly load soil with varying levels of contamination for disposal at four different NYSDEC and ConEd approved contaminated soil disposal facilities. DESI provided oversight of the excavation of contaminated soil and placement of clean fill, installed monitoring wells, evaluated groundwater quality, and reviewed the design of the dewatering and pre-treatment system. DESI evaluated the design of slurry walls, sheet pile walls, and jet-grouted columns; performed test borings to evaluate subsurface soil and rock quality; and developed an alternate design with tie-backs and a waler system, eliminating the use of sheet pile embedded in a slurry wall. This alternate provided significant savings to Conti, in both dollars and a decreased construction duration. DESI also developed a pilot test to demonstrate that for the site conditions, subsidence associated with use of a vibratory hammer and an impact hammer were the same, and that the vibrations generated were within acceptable limits to prevent damage to the adjacent buildings. DESI developed a civil design package for construction of a 90’x45’ groundwater treatment building and canopy structure, including design of the footings, grade beams and the anchoring system for the prefabricated building. DESI also prepared the SWPPP for NYSDEC approval. DESI prepared a Geotechnical Instrumentation Plan for implementation during the installation of the excavation support system, and excavation and backfilling activities; and provided monitoring for vibration, cracks, and vertical and lateral ground movement. DESI reviewed the monitoring data collected on a regular basis, and provided recommendations for corrective actions if movements exceeded allowable limits.
Consolidated Edison (ConEdison)
New York, NY
Conti Environmental & Infrastructure, Inc.
One Cragwood Road
South Plainfield, NJ 07080
Project Cost: $38,000,000
Project Cost: $420000