Field Determination of Vertical Permeability to Air in the Unsaturated Zone
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Field Determination of Vertical Permeability to Air in the Unsaturated Zone GEOLOGICAL SURVEY PROFESSIONAL PAPER 1051 Field Determination of Vertical Permeability to Air in the Unsaturated Zone By EDWIN P. WEEKS GEOLOGICAL SURVEY PROFESSIONAL PAPER 1051 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1978 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Cataloging in Publication Data Weeks, Edwin P., 1936- Field determination of vertical permeability to air in the unsaturated zone. (Geological Survey Professional Paper 1051) Bibliography: p. 41 1. Sediments (Geology) Permeability. 2. Sediment (Geology) United States. I. Title. II. Series: United States Geological Survey Professional Paper 1051. QE471.2.W43 624'.1513 77-10571 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 Stock Number 024-001-03092-6 CONTENTS Page Page Abstract.............................................................................................. 1 Results Continued Introduction........................................................................................ 1 Lubbock, Texas, airport site Continued Previous work.............................................................................. 1 Comparison of results with recharge data............................ 16 Terminology................................................................................ 2 Correction for structural alteration of materials by wetting. 18 Notation...................................................................................... 2 Comparison of results with laboratory data......................... 19 Conversion of English to metric units of measurement............... 3 Discussion of results ............................................................ 20 Theory................................................................................................ 3 Long Island, New York .............................................................. 20 Sources of error in converting air permeability to hydraulic Summary and conclusions.................................................................. 22 conductivity.............................................................................. 4 AIRK-A Fortran IV program for computing hydraulic conductivity Effects of moisture content.......................................................... 5 from pneumatic head readings................................................. 24 Klinkenberg effect........................................................................ 5 Computation of pneumatic head values ...................................... 26 Absorption effects........................................................................ 5 Numerical solution of equation 3 ................................................ 26 The method......................................................................................... 6 The automatic search procedure.................................................. 26 Site inspection ............................................................................. 6 Program verification.................................................................... 27 Instrumentation........................................................................... 6 Input data requirements .............................................................. 28 Data obtained.............................................................................. 7 List of mnemonics and constants used in the AIRK program .... 30 Data analysis............................................................................... 9 AIRK program listing ................................................................. 31 Results................................................................................................ 11 TRIMAT subroutine listing......................................................... 37 Birch Creek Playa, Idaho............................................................ 11 Sample computer output............................................................. 38 Lubbock, Texas, airport site........................................................ 13 Sample output data..................................................................... 38 Comparison of results for different sites and dates.............. 15 References cited.................................................................................. 41 ILLUSTRATIONS Page FIGURE 1. Piezometer nest used to determine pneumatic head differences in the unsaturated zone...................................................................... 7 2. Photograph showing piezometers, manifold, and manometer used to determine pneumatic head...................................................... 7 3. Diagram showing manifold construction.............................................................................................................................................. 8 4. Comparison of pneumatic heads measured at four depths at Lubbock, Tex., airport site A to best-fitting analog simulation............ 9 5. Sample logs and construction diagrams of wells tested at Idaho National Engineering Laboratory, Idaho......................................... 11 6. Comparison of pneumatic heads measured at the Birch Creek Playa, Idaho, site to the best-fitting numerical simulation................. 13 7. Locations of instrumentation used in air-permeability determinations and recharge experiments near the Lubbock, Tex., Regional Airport............................................................................................................................................................................... 14 8. Sample log of test well at Lubbock, Tex., airport spreading site ..............................................................................................:.......... 14 9. Comparison of pneumatic heads measured at five depths at Lubbock, Tex., airport site B to best-fitting numerical simulation ....... 16 10. Cross-section showing unsaturated materials at Nassau County, Long Island, N. Y., Recharge Basin 306......................................... 20 11. Comparison of pneumatic heads measured at two depths at an installation inside Recharge Basin 306, Nassau County, Long Island, N. Y., to the best-fitting numerical simulation................................................................................................................................. 22 12. Sketch showing the relationship between an air-permeability installation and the nodal configurations used to solve for air permeability.. 25 in IV CONTENTS TABLES Page TABLE 1. Summary of vertical air permeability values computed from pneumatic head data obtained from installations at the Birch Creek playa, Idaho......................................,............................................._ 12 2. Depths of piezometers in three installations used to determine vertical air permeability at the Lubbock, Tex., airport spreading site... 14 3. Summary of hydraulic conductivity values computed using pneumatic head data obtained from installations at the Lubbock, Tex., airport spreading site, 1969-72.......................................................................................................................................................... 15 4. Comparison of hydraulic conductivity values estimated from recharge data, from the air-permeability determinations, and from laboratory analyses of drive cores and wireline cores....................................................................................................................... 17 5. Laboratory data for 30 cores from the Ogallala Formation in the Southern High Plains of Texas, showing comparisons of measured hydraulic conductivity to those computed from air permeability ..................................................................................... 19 6. Summary of analyses of pneumatic head data obtained from installations at the Nassau County, Long Island Recharge Basin 306. 21 FIELD DETERMINATION OF VERTICAL PERMEABILITY TO AIR IN THE UN SATURATED ZONE By EDWIN P. WEEKS ABSTRACT INTRODUCTION The vertical permeability to air of layered materials in the unsaturated This report describes application of a method proposed by zone may be determined from air pressure data obtained at depth during a Stallman (1967) to determine, in situ, the vertical permeabili period when air pressure is changing at land surface. Such data may be obtained by monitoring barometric pressure with a microbarograph or ty to air of materials in the unsaturated zone. The method is surveying altimeter and simultaneously measuring down-hole pneumatic based upon the observation that, when the atmospheric head differences in specially constructed piezometers. These data, coupled pressure changes at land surface, air moves to or from the with air-filled porosity data from other sources, may be compared with the unsaturated zone to maintain a pressure balance between air results of electric-analog or numerical solution of the one-dimensional in the soil and the atmosphere. The rate of this air movement diffusion equation to make a trial-and-error determination of the air permeability for each layer. The permeabilities to air may in turn be and the resultant rate of pressure change at depth are converted to equivalent hydraulic conductivity values if the materials are affected by both the permeability and the air-filled porosity well