The New York City Department of Environmental Protection (NYCDEP) has asked the U.S. Geological Survey (USGS) to assist in two major studies: 1) delineation of the source(s) of shallow groundwater and the extent that the Delaware Aqueduct is contributing to local flooding issues, and 2) delineation of the structural, geologic, and hydrologic conditions along proposed tunnel construction paths using advanced surface and borehole geophysical methods.
The NYCDEP needs to determine the source of groundwater and surface water and their possible relation to leakage from the Delaware Aqueduct in upstate New York. The Delaware Aqueduct, which supplies a significant portion of New York City's water supply, has been found to be leaking as much as 35 Mgal/d to the surrounding bedrock and sediment (Ira Stern, Oral commun., 2009). This leakage may have resulted in surface expressions in the form of wet soils and springs, and water level fluctuations in private wells in the towns of Wawarsing and Roseton, NY.
The NYCDEP is developing plans to construct a replacement tunnel along parts of the Delaware Aqueduct. The NYCDEP has requested the USGS to assist in the characterization of the subsurface geology and hydrology along proposed water tunnel construction paths in southeastern New York that may intersect faults and fractures that produce large amounts of groundwater. Recent NYCDEP tunnel excavations beneath Manhattan Island, N.Y., have intersected fractures that produced over 200 gal/min of groundwater flow into the tunnel, highlighting the continued need for the determination of the potential of groundwater-producing fractures and geologic hazards along proposed tunnel excavation areas.
The principal objectives of the Wawarsing/Roseton Tunnel Leakage portion of this study are to:
a) investigate the hydrogeologic framework to obtain a better understanding of the distribution of sediment (clay, sand, and gravel) within the unconsolidated valley-fill deposits, and structural and lithologic variations in the bedrock;
b) characterize the distribution of hydraulic head within both the unconsolidated valley fill sediments and the bedrock to obtain a better understanding of the local groundwater flow system;
c) characterize the potential paths of water from possible tunnel leakages to the flooded areas;
d) monitor the long- and short-term changes in hydraulic heads of the groundwater in the valley fill and bedrock, and seepage related to precipitation and tunnel depressurization tests; and
e) monitor roadbed elevations for subsidence at selected locations using precision surveying techniques to determine if sinkholes are continuing to develop beneath the roadway.
The principal objectives for the portion of this study focused on the hydrogeologic characterization of the proposed New Tunnel routes are to:
1) determine the depth to bedrock, overburden composition, location of major bedrock discontinuities, and changes in rock types along planned tunnel routes using advanced surface geophysical surveys, and use these data to help guide the location of exploration borehole drilling;
2) determine the transmissivity and direction of groundwater flow from intersected faults and fractures within the boreholes using borehole geophysical techniques, estimate specific conductance of ground water within unconsolidated deposits and large fault or fracture zones intersecting the borehole, and determine the regional distribution of transmissive fractures;
3) deliniate lithologic contacts and structural features in the subsurface (faults and fractures) penetrated in boreholes using advanced borehole geophysical techniques, delineate faults or fractures zones in the surrounding bedrock using borehole radar, and determine bedrock heterogeneity using two- and three-dimensional tomograms between boreholes at selected locations;
4) determine the deviation and 3D location of the boreholes and distribution and orientation (true strike and dip) of major faults and fractures penetrated using advanced borehole geophysical techniques; and
5) provide a geophysical data set and 3D images of the major faults and fractures obtained from logging boreholes.
Brown, C.J., Eckhardt, D.A., Stumm, Frederick, and Chu, Anthony, 2012, Preliminary assessment of water chemistry related to groundwater flooding in Wawarsing, New York, 2009–11: U.S. Geological Survey Scientific Investigations Report 2012–5144, 36 p. http://pubs.usgs.gov/sir/2012/5144/.
Stumm, Frederick, Chu, Anthony, Como, M.D., and Noll, M.L., 2012, Preliminary analysis of the hydrologic effects of temporary shutdowns of the Rondout-West Branch Water Tunnel on the groundwater-flow system in Wawarsing, New York: U.S. Geological Survey Scientific Investigations Report 2012–5015, 48 p. http://pubs.usgs.gov/sir/2012/5015/
Stumm, Frederick, Chu, Anthony, and Monti, Jack Jr., 2004, Delineation of Faults, Fractures, Foliation, and Ground-Water-Flow Zones in Fractured-Rock, on the Southern Part of Manhattan, New York, Through Use of Advanced Borehole-Geophysical Techniques: U.S. Geological Survey Open-File Report 2004-1232, 212 p. https://pubs.er.usgs.gov/publication/ofr20041232
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.
Stumm, Frederick, Chu, Anthony, and Lange, A.D. 2001, Use of advanced borehole geophysical techniques to delineate fractured-rock ground-water flow, faults, foliation, and fractures along the western part of Manhattan, New York: U.S. Geological Survey Open-File Report 01-196, 46 p. https://pubs.er.usgs.gov/publication/ofr01196
Stumm, Frederick, Chu, Anthony, Lange, A.D., Paillet, F.L., Williams, J.H., and Lane, J.W., Jr. Use of advanced borehole geophysical techniques to delineate fractured-rock ground-water flow and fractures along water-tunnel facilities in Northern Queens County, New York: U.S. Geological Survey Water-Resources Investigations Report 00-4276, 12 p. http://ny.water.usgs.gov/pubs/wri/wri004276/
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“Characterization of the Fractured Crystalline Bedrock on the Southern Part of Ma”
“Delineation of Ground Water Flow in Fractured Rock in the Southwestern Part of M”
“DELINEATION OF GROUND-WATER FLOW IN FRACTURED ROCK IN THE SOUTHWESTERN PART OF M”