Where is Site-Structural Needed?
Generally, site-structural engineering is needed wherever a construction project places adjacent buildings, infrastructure, facilities or the public at risk. Typically this is the case for construction in the urban environment, where buildings are constructed on or near the lot lines, party walls may be present in existing buildings, and historic structures must be protected during nearby new construction. In the urban environment, construction, especially below ground, presents hazards to surrounding properties.
The following are just a few examples of cities and regions needing site-structural engineering:
New York City: New York City has always been at the forefront of site-structural engineering. The awareness of the need to protect adjacent properties and some of the techniques used to this day were advanced during construction of the city’s subway system in the early twentieth century. Today, regulation of construction risks to adjacent property is uniquely rigorous. The applicable building code provisions (Chapter 33 Safeguards During Construction and Demolition) exceed 80 pages of almost entirely local amendments. In addition, transportation agencies and utilities are commonly granted jurisdiction over nearby construction for the purposes of protecting their facilities.
As so much of New York City has redeveloped in the past generation, the activities that comprise site-structural engineering are practiced there every day. However, some unsophisticated owners, developers, design professionals and contractors, especially in the outer boroughs, cut corners on site-structural issues to speed construction and lower upfront costs.
Washington, DC Metro: In the past decades, Washington, DC and its surroundings have undergone a building boom. Historic public and commercial buildings, as well as residential neighborhoods, have had to be protected if not incorporated into new development. Height limits and favorable soil conditions make deep excavations for new buildings relatively common. Ongoing major infrastructure programs have also exposed adjacent properties to potential impacts.
While the Washington Metropolitan Area Transit Authority and increasing the District of Columbia government require some hazard mitigation for adjacent construction, the state of local practice is relatively poor. Commodity geotechnical reports too often neglect the quality of local soils, resulting in overuse of methods of deep foundations and ground improvement that add construction cost as well as hazards to adjacent structures. Site-structural engineering is left to the contractor alone, missing opportunities to better manage cost and risk through design. This often leading to incomplete and uncoordinated consideration and control of risk. As a result, damage to adjacent buildings, especially due to below-ground construction, is too common.
New England: Much of New England developed around compact urban centers near transportation centers and industries. Revitalization of some of these urban centers has been driving the adaptive reuse of historic buildings, as well as new infill development, increasing the overall density of the community. For some of these communities, these are the first urban construction projects in decades. Protecting existing and sometimes historically significant buildings during adjacent construction can be an unfamiliar problem for the construction industry in these communities.
Mid-Atlantic: The larger cities in the mid-Atlantic region, like Baltimore and Philadelphia, feature large areas of traditional rowhouse and mercantile construction, some of which are subject to redevelopment as these cities become more attractive locations for businesses and residents. As this proceeds, the need to protect viable historic buildings and infrastructure will be increasingly imperative.