Significant Project Features:
- Installation of 1,026 LF of self-hardening slurry wall to a maximum depth of 42 feet below ground surface.
- Installation of 277 jet grout columns to a maximum depth of 40 feet below ground surface to install 595 liner feet of cutoff wall.
- Jet grouting within 2-feet of active underground utilities.
- Project site was located in an active facility and jet grouting production took place around active construction of new buildings.
- Overhead and underground utilities needed to be protected and worked around.
Background
Geo-Solutions Inc. (GSI) was contracted to complete the installation of a groundwater cutoff wall at the Erie Street Former Manufactured Gas Plant located in Elizabeth, New Jersey. The goal of GSI’s work was to build an uninterrupted barrier wall to reduce the flow of pollutants into the surrounding surface water sources and/or groundwater table. The newly installed cut-off wall was tied into cut-off wall sections that were previously installed by Geo-Solutions as this was the third phase of the project included GSI’s involvement as the specialty geotechnical contractor.
Description of Work
Over 30,000 vertical square feet of self-hardening slurry wall was installed using a specially formulated mixture of Slag Cement – Cement – Bentonite (SCCB wall) and water to support the trench sidewalls while excavating and subsequently hardening to create the low permeability cut-off. A Komatsu PC 800 Excavator with an extended stick and 30” wide rock ripper bucket was used to dig the trench and key into underlying bedrock to a maximum depth of 42 feet.
The jet grouting included over 15,000 vertical square feet of wall with columns ranging from 4 to 6 feet in diameter. Columns depths ranged from 16 to 40 feet below ground surface. Several columns were installed within 2 feet of active utilities at varying depths, including around active gas lines. Prior to jet grouting, utilities were exposed, and PVC casing was installed adjacent to them to serve as a drill guide and utility protection. Eight columns were drilled through an existing footer via core holes drilled through the footers. A Soilmec SM14 drill rig and Metax high pressure jet grouting pump were used to perform the work. Spoil trenches were excavated before installation of columns and a vac truck was used for spoil management to maintain a clean site. Wet grab samples and full depth cores were taken during the course of the work. All samples and coring were accepted by the Geotechnical Engineer.
Challenges
- Spoils Management
- Working around multiple above ground and below ground utilities
- Unstable work platform
- Coordination between other contractors on site
