USGS

In Cooperation with the New Hampshire Department of Environmental Services, Waste Management Division

Geology and Preliminary Hydrogeologic Characterization of the Cell-House Site, Berlin, New Hampshire, 2003-04

AVAILABLE ONLINE ONLY

By James R. Degnan, Stewart F. Clark, Jr., Philip T. Harte, and Thomas J. Mack

U.S. Geological Survey Scientific Investigations Report 2004-5282

Complete text of report is available as a PDF (6,004 KB)

Plate 1 is available in .gif format (110 KB)

Abstract

At the cell-house site, thin, generally less than 20-foot thick overburden, consisting of till and demolition materials, overlies fractured crystalline bedrock. Bedrock at the site consists of gneiss with thin discontinuous lenses of chlorite schist and discontinuous tabular pegmatite. Two distinct fracture domains, with principal trends to the west and northwest, and to the north, overlap near the site. The cell-house site shows principal trends common to both domains.

Gneiss is the most abundant rock at the site. Steeply dipping fractures within the gneiss terminate on subhorizontal contacts with pegmatite and on moderately dipping contacts with chlorite schist. Steeply northwest-dipping en Èchelon fracture zones, parallel joint zones, and silicified brittle faults show consistent strikes to the northeast. Gently east-dipping to subhorizontal fractures, sub-parallel to gneissosity, strike northeast.

The impermeable cap, barrier wall, and bedrock surface topography affect ground-water flow in the overburden. There is relatively little ground-water flow in the overburden in the capped area and a poor hydraulic connection between the overburden and the underlying bedrock over most of the site. The overburden beneath the cap may receive inflow through or beneath the barrier wall, or by flow through vertical fractures in the underlying bedrock beneath the barrier wall.

The bedrock aquifer near the river is well connected to the river and head difference in the bedrock across the site are large (greater than 13 ft). Horizontal hydraulic conductivities of 0.2 to 20 ft/d were estimated for the bedrock. Individual fractures or fracture zones likely have hydraulic conductivities greater than the bulk rock. Subhorizontal fractures occur at pegmatite contacts or along chlorite schist lenses and may serve as ground-water conduits to the steeply dipping fractures in gneiss. The effective hydraulic conductivity across the site is likely to be in the low range of the estimated values (0.2 ft/d). Ground water discharges to the river from the bedrock aquifer and is greatest during periods of large river stage fluctuations.

TABLE OF CONTENTS

Abstract
Introduction
      Site Description and History
      Purpose and Scope
      Geologic Setting
      Methods
            Geologic Mapping and Analysis
            Hydrogeologic Analysis
                  Surface Water
                  Ground Water
                   Hydraulic Analysis
                  Geophysical Surveys
                        Ground-Penetrating Radar                        
                        Two-Dimensional Resistivity
                        Borehole Geophysical Logs
Geologic Characterization
       Berlin Area
              Ductile Structures
              Brittle Structures
       Cell-House Site
              Ductile Structures
              Brittle Structures
                   Fracture Zones
                   Faults
                   Fracture Trends
              Geologic Summary
Results of Hydrogeologic Analyses
       Analysis of Surface and Ground-Water Levels
              Head Surfaces and Hydraulic Connections
              Hydraulic Properties
       Geophysical Surveys
              Ground-Penetrating Radar
              Two-Dimensional Resistivity
               Borehole-Geophysical Logs
Preliminary Hydrogeologic Characterization
Summary
Acknowledgments
References
Appendix 1 - Core Logs from Boreholes

Plate

Plate 1 Geologic map of exposed bedrock at the cell-house site, Berlin, N.H.


For more information concerning the research in this report, contact:

Brian Mrazik,
District Chief
USGS
361 Commerce Way
Pembroke, NH 03275

Web site: http://nh.water.usgs.gov
Phone: (603) 226-7807
Email: dc_nh@usgs.gov


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