WSP is a specialist in urban cut and cover construction. Tunnels beneath cities presents several challenges unique to their environment, such as:
- Congested sites
- Historic areas
- Crisscrossing utility and transit lines
- Special underpinning, structural support, and building protection
- High groundwater levels
- Groundwater contamination
- Maintenance of traffic during construction
Our teams have designed and supervised the construction of various types of excavation support systems including soldier piles & lagging, temporary slurry walls, soldier piles in tremie concrete (SPTC) systems, jet grout walls, temporary secant pile walls, soil mix walls, and element walls. Protection schemes for adjacent buildings, tunnels, and utilities designed by our engineers have ranged from conventional underpinning to innovative solutions like micro piles, chemical grouting, jet grouting, compaction grouting, compensation grouting, and ground freezing.
In New York City, WSP performed the construction management services for the Second Avenue Subway to construct a new transit line in a highly congested area of Manhattan, navigating numerous high rise buildings, extensive utilities, historic and fragile buildings, and heavy traffic including several bus lines. The work was accomplished using various support of excavation systems including diaphragm (slurry) walls, secant piles, tangent piles, and soldier piles and lagging.
We also have experience designing underground structures using the top-down method of construction. This technique is an effective means of reducing the impact of construction in urban areas, and can expedite the construction schedule so that surface facilities and traffic can be returned to service sooner.