558 URBAN GEOLOGY Geological Influences on Urban Development Modern engineered works in the urban environment represent relatively large and high-magnitude impacts on the substrate on which they are built Geological site characterization of regional earth materials is thus an absolute necessity before laying the foundation for any large engineered structure, for economic reasons (i.e., to reduce construction costs) as well as for successful structure operation and maintenance and for basic environmental acceptability (Figure 1) Most of the high-impact concerns for site characterization are devoted to a few simple themes The physical nature of foundation earth materials (soil, weak rock, or rock) must be identified as being able to support engineered works without unacceptable structural deformation or outright collapse Geological anomalies that might compromise the integrity of building components or entire engineered work must be detected and delimited Furthermore, ‘bad ground’ that would require premium foundations or difficult construction efforts and higher building costs must be recognized and presented to planners (Figure 1) Cities of The World Literature Series For more than 20 years, the Association of Engineering Geologists (AEG) has fostered the incorporation of geoscience within urban development by publishing an international series of papers (Cities of The World) dedicated to the memory of the outstanding efforts of the late Canadian geological engineer, Robert F Legget (1904–94) The quarterly journal of the AEG (now a joint effort with The Geological Society of America), Environmental and Engineering Geology, seeks and publishes detailed accounts of urban geology, utilizing a standard format (Table 1; see also www.aegweb.org) that serves as a codification of the important elements of urban geology Problematic Conditions of Urban Construction Figure NX size (2.125 inches) rock core recovered by oriented, triple tube coring technique from more than 650 m below Kennedy International Airport, Long Island, New York City, at the site of a proposed liquefied natural gas storage cavern planned by the Brooklyn Union Gas Company (now Key Span Energy Co., Inc.) The rock is complexly mixed Fordham Gneiss and Manhattan Schist and these are select segments of m lengths, all unbroken by natural discontinuities The photograph shows the generally excellent foundation and deep cavern characteristics of New York City bedrock Ruled portion of scale is 15 cm in length; depth marks on core are in metres Photograph by the author Construction in the built environment has to address a variety of geological ‘constraints’ that may be hidden from view during general observation of the existing ground surface Without accurate geological information at the planning and design stages, new construction and urban renewal efforts will almost certainly encounter cost overruns, regulatory compliance infractions, and some type of construction failure Three primary geological considerations (soil, groundwater, and geological dicontinuities) are integral to avoiding such difficulties The nature and thickness of soil units that will bear the dead and live loads transferred downward from the intended construction must be established Likewise, the presence, depth, and potential fluctuation of the groundwater surface below the intended engineered works must be evaluated and related to needs for dewatering without detriment to stability of existing nearby engineered works The soil and groundwater profiles may pose potential excavation problems when deep basements are required to accommodate vehicle parking The presence of and adverse geometrical orientation of geological discontinuities (bedding, joints, shear zones, and faults, to name a few) may