Redeveloping a Remediated MGP Site
Gerald F Nicholls, PE, CHMM, LANGAN
Co-Authors: Steve Ciambruschini, Albert Tashji, Michael Burke, and Seth Vaidya, LANGAN
This presentation will focus on the lessons learned from the bifurcated remediation and redevelopment of the 1.75-acre city block located in the densely populated and coveted Special West Chelsea zoning district in Manhattan, NY. 76 Eleventh Avenue (the “site”). The site is one of 13 parcels that comprise the West 18th Street Gas Works Site, a former manufactured gas plant (MGP). As part of the design and permitting effort for the redevelopment, Langan’s geotechnical and environmental team leveraged institutional knowledge of former MGP site redevelopment and coordinated the environmental requirements and protection of the engineering controls with the project design team. After design, construction began in May 2016 and Langan has provided on-site documentation and inspection services for this $1 billion project. Construction of the site buildings is being sequenced with the first tower topped out, the second underway, and the subgrade portion of the balance of the site scheduled for completion in early 2019. During the site’s design and construction, the following lessons were learned. The presentation will focus on how anticipated and unanticipated concerns were coordinated and addressed.
1. Confining layer and ISS monolith protection during caisson installation—challenges and field documentation and intensive coordination with geotechnical special inspectors.
2. Coring ISS—observations on strength, permeability, groundwater control, and ammonia-like odor. Variability of ISS monolith along boundary.
3. Working around historic structures and landmarks, which caused significant delays to the excavation and SOE installation.
4. Integrating and relocating coal tar recovery wells within new building
5. Incorporating ISS monolith into support of excavation and foundation design—limitations and benefits
6. Coring ISS—observations on strength and permeability. Variability along boundary.
7. Coordinating containment wall changes to accommodate points of entry and foundation elements; protecting containment wall from loading
8. Hazardous benzene disposal and benefit of using nonhazardous facility
9. Odor control
10. MGP structure alignment as shown on historical documents compared to what was photo documented during excavation
11. Cribbing and obstructions during containment wall installation
12. Brownfield tax incentives
13. Challenges to waste characterization and disposal---analytical data versus MGP stigma and odors
Gerry Nicholls manages an environmental project portfolio that includes multi-discipline remediation and redevelopment projects, as well as remediation of legacy or inactive sites in the New York metropolitan region. He works closely with private, institutional, commercial, industrial, and municipal clients and his expertise includes due diligence, site characterization, remedial design, brownfield redevelopment, NAPL recovery, and vapor intrusion mitigation.