ASTM_D_5126_-_D_5126M_-_902010e1.pdf

Designation:D5126/D5126M90(Reapproved 2010)1Standard Guide forComparison of Field Methods for Determining HydraulicConductivity in Vadose Zone1This standard is issued under the fixed designation D5126/D5126M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1NOTEThe units statement in 1.6 and the designation were revised editorially in August 2010.1.Scope1.1 This guide covers a review of the test methods fordetermining hydraulic conductivity in unsaturated soils andsediments.Test methods for determining both field-saturatedand unsaturated hydraulic conductivity are described.1.2 Measurement of hydraulic conductivity in the field isused for estimating the rate of water movement through clayliners to determine if they are a barrier to water flux,forcharacterizing water movement below waste disposal sites topredict contaminant movement,and to measure infiltration anddrainage in soils and sediment for a variety of applications.Test methods are needed for measuring hydraulic conductivityranging from 1 102to 1 108cm/s,for both surface andsubsurface layers,and for both field-saturated and unsaturatedflow.1.3 For these field test methods a distinction must be madebetween“saturated”(Ks)and“field-saturated”(Kfs)hydraulicconductivity.True saturated conditions seldom occur in thevadose zone except where impermeable layers result in thepresence of perched water tables.During infiltration events orin the event of a leak from a lined pond,a“field-saturated”condition develops.True saturation does not occur due toentrapped air(1).2The entrapped air prevents water frommoving in air-filled pores that,in turn,may reduce thehydraulic conductivity measured in the field by as much as afactor of two compared to conditions when trapped air is notpresent(2).Field test methods should simulate the“field-saturated”condition.1.4 Field test methods commonly used to determine field-saturated hydraulic conductivity include various double-ringinfiltrometer test methods,air-entry permeameter test methods,and borehole permeameter tests.Many empirical test methodsare used for calculating hydraulic conductivity from dataobtained with each test method.A general description of eachtest method and special characteristics affecting applicability isprovided.1.5 Field test methods used to determine unsaturated hy-draulic conductivity in the field include direct measurementtechniques and various estimation methods.Direct measure-ment techniques for determining unsaturated hydraulic conduc-tivity include the instantaneous profile(IP)test method and thegypsum crust method.Estimation techniques have been devel-oped using borehole permeameter data and using data obtainedfrom desorption curves(a curve relating water content tomatric potential).1.6 The values stated in either SI units or inch-pound unitspresented in brackets are to be regarded separately asstandard.The values stated in each system may not be exactequivalents;therefore,each system shall be used independentlyof the other.Combining values from the two systems mayresult in non-conformance with the standard.1.6.1 The gravitational system of inch-pound units is usedwhen dealing with inch-pound units.In this system,the pound(lbf)represents a unit of force(weight),while the unit for massis slugs.The rationalized slug unit is not given,unless dynamic(F=ma)calculations are involved.1.7 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.8 This guide offers an organized collection of informationor a series of options and does not recommend a specificcourse of action.This document cannot replace education orexperience and should be used in conjunction with professionaljudgment.Not all aspects of this guide may be applicable in allcircumstances.This ASTM standard is not intended to repre-sent or replace the standard of care by which the adequacy ofa given professional service must be judged,nor should thisdocument be applied without consideration of a projects manyunique aspects.The word“Standard”in the title of this1This guide is under the jurisdiction ofASTM Committee D18 on Soil and Rockand is the direct responsibility of Subcommittee D18.21 on Groundwater andVadose Zone Investigations.Current edition approved Aug.1,2010.Published September 2010.Originallyapproved in 1990.Last previous edition approved in 2004 as D512690(2004).DOI:10.1520/D5126_D5126M-90R10E01.2The boldface numbers in parentheses refer to a list of references at the end ofthe text.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-29