Problem - The New York City Department of Environmental Protection (NYCDEP) is constructing or proposing water tunnels under New York City and areas of southeastern New York (Hudson River Basin). These tunnels can intersect faults and fractures that produce large amounts of ground water. For example, one tunnel excavation intersected fractures that produced over 200 gallons per minute of ground-water flow into the tunnel. Consequently, there is a need to determine the potential of intersecting ground-water producing fractures during tunnel excavation. The use of advanced borehole geophysical techniques by the USGS during tunnel excavations in northern Queens County demonstrated that geophysical techniques can determine the location and characteristics of geologic features that can cause significant ground-water inflow into the tunnel.
The NYCDEP needs the best information possible on the distribution of ground-water producing faults and fractures along the paths of proposed tunnel excavations. Conventional borehole cores alone cannot adequately provide this information. Therefore, the USGS and the NYCDEP are continuing a project that uses advanced borehole geophysical techniques to study the subsurface geologic features and fractured-rock ground-water-flow system in southeastern New York (Ulster, Orange, Westchester, and Bronx Counties), especially in New York City (New York, Queens, Kings, and Bronx Counties).
Objectives - The objective of the study is to use advanced borehole geophysical techniques to identify the location and orientation of faults and fractures intersected by boreholes along the proposed path of water tunnels being constructed by New York City and to provide information on the quantity and relative quality of ground water flowing in some of these geological structures. New advancements in digital imaging technologies can produce three-dimensional images, known as virtual cores, of the rock surrounding the borehole. The virtual cores can be rotated into any orientation to allow a complete visualization and analysis of fractures and faults intersected by the borehole.
Specific objectives are to:
- Delineate lithologic contacts and subsurface geologic structures, such as faults and fractures, penetrated by the boreholes by using advanced borehole geophysical techniques. Delineate faults or fractures zones in the surrounding bedrock as far as 30 meters from the borehole by using borehole radar. Determine bedrock heterogeneity between boreholes at selected locations by using two- and three-dimensional tomograms.
- Determine the transmissivity of faults and fractures intersected by the boreholes and the direction of ground-water flow in these geologic structures.
- Determine the deviation and three-dimensional location of the boreholes and distribution and orientation (true strike and dip) of major faults and fractures penetrated using advanced borehole geophysical techniques.
- Provide to NYCDEP geophysical data sets and three-dimensional visualization information on the major faults and fractures and potential water-bearing zones.
Related Publications
- Stumm, Frederick and Chowdhury, Shafiul, 2003, Delineation of ground water flow in fractured rock in the southwestern part of Manhattan, New York, through use of advanced borehole geophysical methods: Ground Water Monitoring & Remediation, v. 23, no. 3 (Summer 2003), p. 42-49.
- Stumm, Frederick, Chu, Anthony, and Lange, A.D., 2003, Delineation of ground-water flow in fractured rock in the southwestern part of Manhattan, New York, through use of advanced borehole geophysical methods, in Proceedings of the Environmental and Engineering Society, 2003, Symposium on the Application of Geophysics to Environmental and Engineering Problems, April 6-10, 2003, San Antonio, Texas, p. 758-771.
- Stumm, Frederick, Chu, Anthony, Joesten, P.K., and Lane, J.W., Jr., 2007, Geohydrologic assessment of fractured crystalline bedrock on the southern part of Manhattan, New York, through the use of advanced borehole geophysical methods: Journal of Geophysics and Engineering, v. 4, no. 3, p. 245-252, doi:10.1088/1742-2132/4/3/S02.
Project Location by County Delaware County, NY, Greene County, NY, Schoharie County, NY, Sullivan County, NY, Ulster County, NY, Rockland County, NY, Bronx County, NY, Kings County, NY, New York (Manhattan) County (FIPS 36061), NY, Richmond County, NY, Westchester County, NY, Putnam County, NY, Dutchess County, NY, Orange County, NY, Columbia County, NY
