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Scientific Investigations Report 2014–5228

Prepared in cooperation with the U.S. Environmental Protection Agency

Geophysical Log Analysis of Selected Test and Residential Wells at the Shenandoah Road National Superfund Site, East Fishkill, Dutchess County, New York

By Richard J. Reynolds, J. Alton Anderson, and John H. Williams

Thumbnail of and link to report PDF (2.38 MB)Abstract

The U.S. Geological Survey collected and analyzed geophysical logs from 20 test wells and 23 residential wells at the Shenandoah Road National Superfund Site in East Fishkill, New York, from 2006 through 2010 as part of an Interagency Agreement to provide hydrogeologic technical support to the U.S. Environmental Protection Agency, Region 2. The geophysical logs collected include caliper, gamma, acoustic and optical televiewer, deviation, electromagnetic-induction, magnetic-susceptibility, fluid-property, and flow under ambient and pumped conditions. The geophysical logs were analyzed along with single-well aquifer test data and drilling logs to characterize the lithology, fabric, fractures, and flow zones penetrated by the wells. The results of the geophysical log analysis were used as part of the hydrogeologic characterization of the site and in the design of discrete-zone monitoring installations in the test wells and selected residential wells.

Most of the logged test and residential wells penetrated gneiss of the Hudson Highlands Complex or dolostones in the Wappinger Group, and some wells penetrated both the dolostone and gneiss. The bedrock fabric reflects the regional northeast-southwest structural trend, as well as localized folding, and includes foliation in the gneiss and bedding in the dolostone. Many fractures were oriented along the bedrock fabric, whereas others were orthogonal to the fabric.

Total wellbore transmissivity of the wells was estimated from short-term, single-well aquifer test data through the use of the Cooper-Jacob analytical solution. An empirical relation was established to estimate total wellbore transmissivity from specific-capacity data for wells with insufficient transient drawdown measurements. Wellbore transmissivity estimates ranged from 0.36 to 370 feet squared per day (ft2/d), whereas specific capacities ranged from 0.03 to 2.1 gallons per minute per foot ((gal/min)/ft).

Transmissivity and hydraulic heads of individual fracture zones were estimated from the total wellbore transmissivity and flow logs through use of an analytical model based on the Thiem equation. The model-estimated transmissivity of 95 fracture zones delineated in the 43 wells ranged from 0.25 to 340 ft2/d, with a median value of 6.7 ft2/d. The difference between model-estimated fracture-zone heads and the composite heads in each well ranged from less 0.01 to more than 10 feet (ft). Flow-log analysis generally provided an order of magnitude estimate for the fracture-zone hydraulic-head difference on the basis of a comparison of estimated and measured values.

The geophysical logs and their analyses are available for display and download from the U.S. Geological Survey, New York Water Science Center, online geophysical log archive (http://ny.water.usgs.gov/maps/geologs/) in LAS (Log ASCII Standard), PDF, and WellCad formats.

First posted March 20, 2015

  • Geophysical Log Archive
     The USGS New York Water Science Center has developed an online geophysical log archive where the logs and log analysis of the Shenandoah Road Superfund site wells, as well as many others throughout the State, can be viewed or downloaded.
  • WellCad reader download
    The locations of the Shenandoah Road National Superfund Site wells are shown on the index map. The user can zoom-in to the well cluster located just east of Fishkill, N.Y., to expand the view of the wells logged.  Clicking on an individual well will bring up a menu of the available log formats, which are LAS, PDF, and WellCad Reader. WellCad Reader is available online free of charge.

For additional information, contact:
Director, New York Water Science Center
U.S. Geological Survey
425 Jordan Road
Troy, NY 12180
(518) 285-5600
http://ny.water.usgs.gov

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Suggested citation:

Reynolds, R.J., Anderson, J.A., and Williams, J.H., 2015, Geophysical log analysis of selected test and residential wells at the Shenandoah Road National Superfund Site, East Fishkill, Dutchess County, New York: U.S. Geological Survey Scientific Investigations Report 2014–5228, 30 p., http://dx.doi.org/10.3133/sir20145228.

ISSN 2328-0328 (online)



Contents

Abstract

Introduction

Bedrock Geology

Structural Geology

Surficial Geology

Description of Wells

Data Collection

Geophysical Log Analysis

Online Geophysical Log Archive

Summary

Selected References

Appendix 1. Geophysical Log Analysis of Three Selected Wells at the Shenandoah Road National Superfund Site, Dutchess County, N.Y

Explanation Of Geophysical Log Column Headings

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