Geologic Mapping in Urban Settings

• The many reasons why the geology of our cities must be mapped in detail.

  •	Sediments and rocks beneath the cities deposited during the last Ice Age provide foundation conditions that support our skylines. The extent of these complex deposits and their favorable or unfavorable conditions for construction of any type has not been mapped.
  •	Brownfield reclamation, redevelopment, and associated costs are dependent in large part on the near-surface geology, which is poorly known.
  •	The ground beneath our cities holds wastes, spills, and debris from generations of inhabitants and businesses. Some of these areas have been redeveloped into parks and playgrounds and pose a real hazard. The near-surface geology, which controls the local migration of contaminants, has not been mapped.
  •	Costs of excavation and fill, required for infrastructure development, depend on the nature and thickness of glacial deposits and rock at construction sites and in source areas where suitable fill can be obtained.
  •	Development of underground space to quarry rock for aggregate, tunnel for transportation or drainage control, or develop for warehouse space requires geologic mapping.
  •	Sources of aggregate for building and infrastructure upgrades are becoming depleted in areas closest to cities. Geology in large part dictates where the highest quality, closest, and least expensive resources can be obtained.
  •	Occurrence and severity of hazards, such as building settlement, subsurface piping, and flooding, and susceptibility to earthquake shaking, depend in large part on the nature and distribution of geologic deposits.
  •	For those cities on a Great Lake, issues such as shoreline erosion, shoreline protection measures, sedimentation, beach replenishment, shoreline redevelopment, and near-shore lake bottom paving all require geologic understanding.
  •	The suitability of land for preservation, restoration, or creation of open space, wetlands, and surface water bodies depends in part on the capability of geologic materials to successfully support the proposed use.
  •	The cost and long-term performance of landfills and other waste disposal sites depend on the geologic setting.
  •	The cost of containment and cleanup of contaminants either accidentally or deliberately introduced would depend in large part on the geologic characteristics of the ground in the area of the release.
  •	The ability of ground water to recharge aquifers depends on variability of both the geologic materials and land use. Knowledge of the distribution of these materials would allow strategic land-use planning to better coordinate efforts to increase recharge and decrease runoff.