vvEPA
           United States
           Environmental Protection
           Agency
Office of Solid Waste
and Emergency Response
Washington DC 20460
July 1986
           Solid Watte
           Criteria for Identifying
           Areas of Vulnerable
           Hydrogeology Under the
           Resource Conservation
           and Recovery Act

           Appendix A

           Technical Methods for
           Evaluating
           Hydrogeologic
           Parameters
           Interim Final

-------
                                                  0^,;   .'LICY DIRECTIVE NO.

                                                 9472  -00-2A
                       TABLE OF CONTENTS

                           Appendix A
Table of Contents                                     i
List of Figures                                       iii
List of Tables                                        iii
1.0 Methods to Characterize Hydraulic Conductivity.... 1-1

   1.1 Well Construction Considerations	1-3

     1.1.1 Wells Requiring Screens	1-4

     1.1.2 Wells Not Requiring Screens	1-5

   1. 2 Well Development	1-6

   1.3 Data Interpretation and Test Selection
       Considerations	1-6

   1.4 Single Well Tests	1-8

     1.4.1 Methods for Moderately Permeable Formations
           Under Confined Conditions	1-8

     1.4.2 Methods for Extremely Tight Formations
           Under Confined Conditions	1-15

     1.4.3 Methods for Moderately Permeable Materials
           Under Unconfined Conditions	1-17

   1. 5 Multiple Well Tests	1-24

   1. 6 Fractured Media	1-24

2.0 Determination of- Effective Porosity	2-1

   2.1 Specific Yield in the Unconfined Aquifer	2-1

   2 . 2 Confined Aquifers	2-5

   2.3 Tabulated Values of Effective Porosity	2-5

3.0 Determination of Hydraulic Gradient	3-1

4.0 References	4-1

   4.1 References for Section 1.0	4-1

-------
                                               OSWER POLICY DIRECTIVE j:-j




                                              9472•00-2A
4.2 References  for  Section 2.0	 7. ..74-2


4. 3 References  for  Section 3.0	,.	4-2
                             ii

-------
                        LIST OF FIGURES
1.4-1  Geometry and Variable Definitions for Slug
       Tests in Confined Aquifers	1-10

1.4-2  Schematic Diagram for Pressurized Slug
       Test Method in Consolidated and
       Unconsolidated Materials	1-17

1.4-3  Variable Definitions for Slug Tests in
       Unconfined Materials	1-20

1.4-4  Curves Defining Coefficients A, B, and
       C in Equations 13 and 14 as a function
       of the Ratio L/rw	1-23

2.0-1  Concept of Specific Yield veiwed in terms of
       the Unsaturated Moisture Profile Above the
       Water Table	2-2

2.0-2  Relationship between Specific Yield and
       Grain Size	2-4

3.0-1  Diagram of How Temporal Changes in Hydraulic
       Gradient Affect the Flow Paths of Ground-Water.3-3

3.0-2  Illustration of Mounding in the Unsaturated
       Zone	3-4

3.0-3  Diagram of Mounding in the Saturated Zone	3-6
                         LIST OF TABLES
1.4-1  Values of the Function F (<<,£) for use in
       the conventional and pressurized slug tests.... 1-12
                              iii

-------
                   FIELD METHODS TO DETERMINE
                     HYDRAULIC CONDUCTIVITY
SECTION 1.0

This section discusses methods available for the determination

of fluid conductivity under field conditions.  As most of these

tests will use water as the testing fluid, either natural for-

mation water or water added to a borehole or piezometer, the

term hydraulic conductivity will be used for the remainder of

this section.  Before testing for hydraulic condu&tivity, the

first step is to characterize the geology of the site.  This

initial characterization will aid i'n the design of well locations

The investigator should consult the RCRA Ground-Water Monitoring

Technical Enforcement Guidance Document, U.S.EPA (Draft) 1985

(TEGD) for information on site characterization.


The owner/operator must identify areas of high and low hydraulic

conductivity (K) within each formation, because such variations

in K can create irregularities in ground water flow paths.

Areas of high hydraulic conductivity represent areas of greater

ground water flow and, if contaminants are present, zones of

potential migration.


Hydraulic conductivity measurements must define both vertical

and horizontal hydraulic conductivity across an owner/operator's

regulated site.  In assessing the completeness of an owner/

operator's hydraulic conductivity measurements, the reviewer
                              1-1

-------
should also consider results trom the boring program used to
characterize the site geology.  Zones of high permeability or
fractures identified from drilling logs should have been con-
sidered in the determination of hydraulic conductivity.
Additionally, information from coring logs can be used to
refine the data generated by slug or pump tests.

The location of wells, selection of screened intervals, and the
appropriate tests depend upon the specific site under invest-
igation.  The person responsible for such selections should be
a qualified hydrogeologist or geotechnical engineer experienced
in the application of established principles of contaminant
hydrogeology and ground water hydraulics.

To estimate hydraulic conductivity,  single well methods are
the preferred method since they do not average the effects
of geologic heterogeneities. In addition, the methods for
field determination of hydraulic conductivity are restricted
to well or piezometer tests applicable below existing
water tables.  Determination of travel times of leachate and
dissolved solutes above the water table usually require the
application of unsaturated flow theory.  Methods for calculating
travel times in unsaturated zones are detailed in Appendix C.

Standard reference texts on ground water hydraulics and con-
taminant hydrogeology that should be consulted include:  Bear
(1972), Bouwer (1978), Freeze and Cherry (1979), Stallman (1971),
and Walton (1970) .
                              1-2

-------
                                                          D(S£cm.
1.1    WELL-CONSTRUCTION CONSIDERATIONS

The purpose of using properly constructed wells for hydraulic

conductivity testing is to assure that test results reflect

conditions in the geologic interval being tested, rather than

the conditions caused by well construction.  In all cases,

diagrams showing all details of the actual well or borehole

constructed for the test should be made, as well as detailed

narrative description.



Detailed discussions of well installation, construction, and
                                                 r'-
development methods are given by Bouwer (1978), pages 160-180,

Acker (1974), Johnson (1975), and the TEGD, Chapter 3.



The TEGD should be consulted for information concerning well

drilling, construction,  and development considerations.  However,

the TEGD is concerned primarily with ground water quality mon-

itoring wells.  Boreholes suitable for measuring hydraulic

conductivity may not necessarily also be suitable for ground

water quality monitoring, due to considerations unique to mon-

itoring (such as the need for inert casing, possible need for

pumps to be installed, etc.).  The TEGD discusses these differ-

ences in more detail.

1.1.1    Wells Requiring Well Screens

Well screens placed opposite the interval to be tested should

be constructed of materials that are compatible with the fluids

to be encountered.  The screen slot size should be determined to

minimize the inflow of fine-grained material to the well during

development and testing. In addition,  hydraulic conductivity



                              1-3

-------
information generally provides average values for the entire area



across a well screen.  For more depth discrete information, well



screens will have to be shorter.  If the average hydraulic con-



ductivity for a formation is required, entire formations may have



to be screened.  Bouwer (1978), and Johnson (1975) give a summary of



guidelines for sizing well screens.





The annulus between the well screen and the borehole should be



filled with an artificial gravel pack or sand filter.  Guide-



lines for sizing these materials are given by Johrfson (1975).



For very coarse materials, it may be acceptable to allow the



materials from the tes'ted zone to collapse around the screen



forming a natural gravel pack.





The screened interval should be isoloated from overlying and



underlying zones by materials of low hydraulic conductivity.



Generally, a short bentonite plug is placed on top of the



material surrounding the screen, and cement grout is placed in



the borehole to the nextihigher screened interval (in the case



of multiple screen wells), or to the land surface for single



screen wells.





Although considerations for ground water quality sampling may



dictate different minimum casing and screen diameters, the



recommended guideline for hydraulic conductivity characterization



studies is that wells to be tested by pumping, bailing,  or injection



in coarse-grained materials should be at least 4 inches  inside



diameter. Wells to be used for testing materials of low  hydraulic





                              1-4

-------
conductivity by sudden removal or injection of a known volume

of fluid should be constructed with as small a casing diameter

as possible to maximize measurement resolution of fluid level

changes.  Casing sizes of 1.25 to 1.50 inches usually allow

this resolution while enabling the efficient sudden withdrawal

of water for these tests.


1.1.2  Wells Not Requiring Well Screens

If the zone to be tested is sufficiently indurated that a well

screen and casing is not required to prevent caving/ then it is
                                                 rr-   ' '  .
preferable to use a borehole open to the zone to be tested.

These materials generally are those having low to extremely

low hydraulic conductivities.  Consolidated rocks having high

conductivity because of the presence of fractures and solution

openings may also be completed without the use of a screen and

gravel pack.  Uncased wells may penetrate several zones for

which hydraulic conductivity test are to be run.  In these

cases, the zones of interest may be isolated by the use of

inflatable packers.

1.2  WELL DEVELOPMENT

For wells that are constructed with well screens and gravel

packs, and for all wells in which drilling fluids have been

used that may have penetrated the materials to be tested, ade-

quate development of the well is required to remove these

fluids and to remove the fine-grained materials from the zone

around the well screen.  Development is carried out by methods

such as intermittent pumping, jetting with water, surging, and
                              1-5

-------
bailing.  Adequate development is required to assure maximum



communication between fluids in the borehole and the zone to be



tested.  Results from test run in wells that are inadequately



developed will include an error caused by-loss of fluid poten-



tial across the undeveloped zone, and computed hydraulic con-



ductivities will be lower than the actual value.  Bouwer (1978),



Johnson (1975), and the TEGD give further details on well



development including methods to determine' when adequate



development has occurred.









1.3  DATA INTERPRETATION AND TEST SELECTION CONSIDERATIONS



Hydraulic conductivity may be determined  in wells that are



either cased or uncased as described in Section  l.l.  The tests



all involve disturbing the existing fluid potential in the



tested zone by withdrawal from or injection of fluid into a



well either as a slug over an extremely short period of time,



or by continuous withdrawal or injection of fluid.  The



hydraulic conductivity is determined by measuring the response



of the water level or pressure in the well as a function of




time since the start of the test.  Many excellent references



are available that give the derivation and use of the methods



that are outlined below, including Bouwer (1978), Walton



(1969), and Lohman (1972).
                              1-6

-------
The selection of  a  particular  test method  and data  analysis
technique requires  the  consideration  of  the  purposes  of  the
test, and the geologic  framework  in which  the test  is to be
run.  Knowledge of  the  stratigraphic  relationships  of the zone
to be tested and  both overlying and underlying materials should
always be used to select  appropriate  test  design  and  data
interpretation methods.

The equations given for' all  computational  methodsvgiven  here
and in the above  references  are based on idealized  .models
comprising layers of materials of different  hydraulic conduc-
tivities.  The water-level response caused by disturbing the
system by the addition  or removal of  water can be similar for
quite different systems.  For  example, the response of a water-
table aquifer and a leaky, .confined aquifer  to pumping can be
very similar.  Consequently, it is not considered acceptable
practice to obtain  data from a hydraulic conductivity test and
interpret the type  of hydraulic system present without sup-
porting geologic  evidence.

The well test methods are discussed under  the following  two
categories:  1) methods applicable to coarse-grained  materials
and tight to extremely*tight materials under confined conditions;
and 2) methods applicable to unconfined  materials of  moderate
                              1-7

-------
permeability.   The  single well tests integrate the effects of
heterogeneity  and anisotropy.   The effects of boundaries such
as streams  or  less  permeable materials usually are not detec-
table with  these methods  because  of the small portion of the
geologic  unit  that  is  tested.
1.4  SINGLE WELL TESTS
The tests for  determining  hydraulic conductivity with a single
well are discussed  below  based  on  methods  for confined and
unconfined conditions.  The methods are usually  called slug
tests because  the test  involves removing a slug  of water
instantaneously from a  well and measuring  the recovery of  water
in the well.   The method  was first developed  by  Hvorslev (1951),
whose analysis did  not  consider the effect of fluid stored in
the well.  Cooper and others (1967)  developed a  method that
considers well bore storage.   However,  their  method only
applies to wells that are  open  to  the  entire  zone to be tested
and that tap confined aquifers.  Because of the  rapid water-
level response in coarse materials,  the tests are generally
limited to zones with a transmissivity  of  less than about
70 cmVsec  (Lohman, 1972).  The method  has been  extended to
allow testing of extremely tight formations by Bredehoeft  and
Papadopulos (1980).  Bouwer and Rice (1976) developed a method
for analyzing slug  tests  for unconfined aquifers.
1 .4.1    Method for Moderately Permeable Formations  Under
         Confined Conditions
1.4.1.1  Applicability.  This method  is applicable  for  testing
zones to which the entire zone is open to  the well  screen  or
                            1-8

-------
open borehole.  The method  usually  is  used  in materials of
moderate hydraulic conductivity  which  allow measurement of
water-level response over a period  of  an hour to a few days.
More permeable  zones can be tested  with rapid response water-
level recording equipment.   The  method assumes that the tested
zone is uniform in all  radial  directions from the test well.
Figure 1.4-1 illustrates the test geometry for this method.

1.4.1.2  Procedures.  The slug test is run  by utilizing some
method of removing a known  volume of water  from the well bore
in a very short time period and  measuring the recovery of the
water level in  the well.  The  procedures are the same for both
unconfined and confined aquifers.   Water is most effectively
removed by using a bailer that has  been allowed to fill and
stand in the well for a sufficiently long period of time so
that any water-level disturbance caused by  the insertion of the
bailer will have reached equilibrium,   in permeable materials,
this recovery time may  be as little as a few minutes.  An
alternate method of effecting  a  sudden change in water level  is
the withdrawal of a weighted float.  The volume of water
displaced can be computed using  the known submersed volume of
the float and Archimedes' principle (Lohman,  1972).
Water-level changes are recorded using either a pressure trans-
ducer and a strip chart recorder, a weighted steel tape, or an
electric water-level probe.  For  testing permeable materials
that approach or exceed 70  cm2/sec,  a  rapid-response transducer/
recorder system is usually  used  because essentially full reco-
very may occur  in a few minutes.  Because the rate of water-
level response decays with  time, water-level or pressure
                           1-9

-------
                               WELL CASING
                               WELL SCREEN
                                / CONFINING LAYER
Figure 1.4-1—Geometry  and variable  definition for
             slug tests  in confined aquifers.
                         1-10

-------
changes should be  taken  at  increments  that are  approximately
equally spaced in  the  logarithm  of  the time since fluid
withdrawal.  The test  should  be  continued  until the water level
in the well has recovered to  at  least  85 percent of the initial
pre-test value.

1.4.1.3  Calculations.   Calculations for determining hydraulic
conductivity for moderately permeable  formations under confined
conditions can be  made using  the following:

   a.  Determine the transmissivity of the tested zone by
       plotting the ratio h/ho on an arithmetic scale against
       time since  removal of  water  Ct)  on  a logarithmic scale.
       The observed fluid potential in the well during the test
       as measured by  water level or pressure  is h, and ho is
       the fluid potential  before the  instant of fluid
       withdrawal.  The  data  plot is superimposed on type
       curves, such as those  given  by  Lohman (1972), Plate 2
       or plotted  from Table 1.4-1 with the h/ho and time axes
       coincident.  The  data  plot is moved horizontally until
       the data fits one of the  type curves.  A value of time
       on the data plot  corresponding  to a dimensionless time
       (0) on the  type curve  plot is chosen, and the transmis-
       sivity is computed from the  following:
                          T  = 6rc2>                         (1)
                                t
       where rc  is  the  radius  of  the  casing  (Lohman,  1972,  p.  29)
                             1-11

-------
              TABLE 1.4-1
   Values of the function  F(a,6)  for use in
the conventional and pressurized  slug tests.
      Source: Papadopulos  et.al.  (1973)
rt/r,'
0.001
0.002
0.004
0.006
0.008
0.01
0.02
0.04
0.06
0.08
0.1
0.2
0.4
0.6
0.8
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
20.0
30.0
40.0
50.0
60.0
80.0
100.0
200.0
a - 10-«
0.9994
0.99S9
0.99SO
0.9972
0.9964
0.9956
0.9919 .
0.9S48
0.9782
0.9718
0 9655
0.9361
0.8828
0.8345
0.7901
0.7489
0.5800
0.4554
0.3613
0.2S93
0.2337
0.1903
0.1562
0.1292
0.1078
0.02720
0.01286
0.008337
0.006209
0.004961
0.003547
0.002763
0.001313
o - 10"
0.9996
0.9992
0.9985
0.9978
0.9971
0.9965
0.9934
0.9S75
0.9819
0.9765
0.9712
0.9459
0.8995
0.8569
0.8173
0.7801
0.6235
0.5033
0.4093
0.3351
0.2759
0.2285
0.1903
0.1594
0.1343
0.03343
0.01448
O.OOSS98
0.006470
0.005111
0.003617
0.002803
0.001322
a - 10-«
0.9996
0.9993
0.9987
0.9982
0.9976
0.9971
0.9944
,0.9894
0.9846
0.9799
0.9753
0.9532
0.9122
0.8741
0'.83S3
0.8045
0.6591
0.5442
0.4517
0.3768
0.3157
0.2655
0 2243
0.1902
0.1620
0.04129
0.01667
0.009637
0.006789
• 0.005283
0.003691
0.002845
0.001330
a - 10-»
0.9997
0.9994
0.9989
0.9984
0.9980
0.9975
0.9952
0.9908
0 9S66
0.9824
0.9784
0.9587
0.9220
0.8875
0.8550
0.8240
0.6889
0.5792
0.4891
0.4146
0.3525
0.3007
0.2573
0.2208
0.1900
0.05071
0.01956
0.01062
0.007192
0.005487
0.003773
0.002890
0.001339
a - 10-"
0.9997
0.9995
0.9991
0.9986
0.9982
0.9978
0.9958
0.9919
0.9881
0.9844
0.9807
0.9631
0.9298
0.8984
0.8686
0.8401
0.7139
0.6096
0.5222
0.4487
0.3865
0.3337
0.2888
0.2505
0.2178
0.06149
0.02320
0.01190
0.007709
0.005735
0.003S63
0.002938
0.001348
                  1-12

-------
             TABLE 1.4-1, continued

Extended values  of F(ct,S) for  use  in slug tests.
    Source:  Bredehoeft and Papadooulos (1980).
p
c.oocooi
c.oocoo?
G.onc on*
c.oocoot
c.orc OOP,
O.orcoi
C.OPCO?
O.nnr o*
o.oocr*
o.opr PB
O.OOCI
c.oncr1
O.OOC*
c.ocr*
o.onrh
C.OPl
C.OCi
c.op*
c.cnt
O.cnt
C.Ol
0.02
0.0*
n.o*
C.OP
0.1
0.2
0.4
O.C
O.f>
1.
t «
«.
t.
e.
1C.
?c.
4C.
»-C.
MC.
inc.
?no.
• «C.
60C.
enc.
100C.
o = 0.1
P.°C93
P. 9990
u.sKbf
0.99«?
1.0900
O.V977
0.996S
J.'i'SSS
n.944«
0.9<)lb
.i.oq?"!
P.-J69C
O.'?0^'-
O.^PZJ
T.*79*
O.T765
n.9«,70
0.«»%3P
0.9*17
0.93??
0.9?3t
0.890*
O.fl*?l
o.en*f
n.773*
0.7*59
0.h41P
0.509?
(•..*? ?7
0.159(>
0.3117
0. 1 Tbf-
1.nP7tl
0.065?7
0.0?Q*3
n.(n065
0.01 41l*
o.oneteo
n. OP4167
O.CC3?*?
0.002J77
3.nni?7]
r.noo'-"*07
o.ooo*!-'''
C.000?l«0
n.ocn?5lo
0 = 0.2
O.s-*«in
0.99ff.
a.99tn
C.9-J7C,
0.9971
0.9966
0.99':?.
0.99if
0.99J?
0.99C9
n.9-<;o
0.98?7
0.97S7
0.97SJ
0.9713
C.9-J79
U.9S*6
0.93i7
0_9?1 1
0.90S9
O.fl9f2
O.HS42
P. 7980
0.7t»»,
0.7190
o.eeei
C.S77*
p.**;p
0.36*?
O.?h7?
0.2*,*P
0. Ibl9
0.17t9*
.C.O*S99
0.03tbe
0.0?t7C
0.013M
O.nn»c^e
C. 01*318
C.Oft}?!*
o.oo;<;E9
O.on]?t*
0.000ft?9?
O.OOC41PP
C.OOC3137
o.oocpsoe
0=0.5
0.996.
0.9977
r,.9°t.e
0.9V61
0.99*%
P. 99*9
0.99?9
a.9i-9o
0.9877
0.9BSP
n.9B»i
0.977*
0.9»>fl5
P.961S
O.-^S'
".950=
0.93P7
P. 9031
O.Sfc?^
n.86<>*
n.ssoe
0.79*7
0.721*
0.'>fr97
n.6£89
o.svm
U.*'99
0.356*
0.2Bfe*
0.2397
P.20M
0.120?
P.0b*?0
0.0*3 31
0.03?1?*
0.026"p
0.01?.cA
0.00617*
0.00*??9
0.003163
n.oo?s?ft
0.00175P
0.000*?72
0.000*177
0.0001131
0.0002SO*
(1 = 1
C.9977
0.9968
C.99SS
C.994S
C.9936
0.9979
T.9900
e.9e«,e
C.98P7
o.9nno
C.'»777
0,96P7
0.9%dO
O.o*f?>
0."3P5
0.93JS
0.904W
0.3606
O.«*19
0.8202
O.P.017
C.7336
0.6*89
0.5919
0.5*A6
O.S1?7
c.*oio
O.?902
O.J311
0.1931
0. 1663
C.0991?
0.05521
P. 03830
0.0?9^3
0.0?376
0.01719
O.OOM71
0.00*1 3?
P.00310R
0.00?*87
0.00)2*7
0.00062*2
9.000*1*2
0.00n31?3
0.n002«Q9
0=2
P.996P
0.99S5
0.^93^
0.9)
0.001Z3P
0.000*195
0.000*1* 1
0.00031 10
0.0002*90
U=5
0.99*8
0.9927
0.9P.98
0.9876
0.9857
O.VCU1
0.9776
0.9687
0.9619
0.9562
0.95 1-2
0.9321
0.9061
O.BP69
O.B71 1
0.8576
0.6075
0.7*39
0.7Q01
0.6662
0.636*
0.5*50
0,4*5*
0.3P7?
0.3*69
0.3168
0.2313
0.1612
0.1280
0.1077
0.09375
0.059*0
0.03621
0.02663 '
0.0212S
0.0177*
0.0099*3
0.005395
O.f'03726
0.002853
0.002313
0.00119*
0.0006085
0.000*087
0.0003078
0.0002*69
0=/10
0.9923
0.989*
0.9853
0.982?
0.9796
0.9773
0.9683
0.9556
0.9*6*
0.9387
0.931P
0.9059
0.8711
0.8*58
0.8253
0.8079
0.7*50
0.666*
0.6178
0.5797
0.5*92
O.»517
0.3556
0.3030
0.2682
0.2*28
0.17*0
0.1207
0.09616
0.0613*
0.07120
0.0*620
0.02908
0.02185
0.01771
0.01*99
0.006716
0.00*696
0.003**5
0.002668
0.002161
0.001 1*9
fl.0005***
0.000*016
0.0003035
0.0002**0
                     1-13

-------
       The type curves plotted  using  data in Table 1.4-1  are not
       to be confused with  those  commonly referred to as 'Theis
       Curves' which are  used for pumping tests  in confined
       aquifers (Lohman,  1972).   The  type curve  method is a
       general technique  of detemining  aquifer parameters when
       the solution to the  descriptive  flow  equation involves
       more than one unknown parameter.   Although both the
       storage coefficient  and  transmissivity  of the tested
       interval can be determined with  the type  curve method
       for slug tests, determination  of  storage  coefficients is
       beyond the scope of  this report.   See Section 1.4.1.4
       for further discussion of  the  storage coefficient.

       If the data in Table 1.4-1  are  used, a type curve for
       each value of a is prepared by plotting F(a,6) on the
       arithmetic scale and dimensionless time (B)  on the
       logarithmic scale  of semi-log  paper.

   b.  Determine the hydraulic  conductivity  by dividing the
       transmissivity by  the thickness  of the  tested zone.

1.4.1.4  Sources of Error.  The errors  that  can  arise in
conducting slug tests can be of three types:   those resulting
from the well or borehole construction,  measurement errors,
and data analysis error.
Well construction and development errors.  This  method assumes
that the entire thickness of the  zone of interest is open to
                              1-14

-------
                                                OSWfER POLICY DIRECTS ...

                                              9472-00-2A
the well screen or boreholes and that flow  is principally radial.
                                             %
If this is not the case, the computed hydraulic conductivity
may be too high.  If the well is not properly developed,  the
computed conductivity will be too low.

                        /
Measurement errors can result from determining or recording the
fluid level in the borehole and the time of measurement
incorrectly.  Water levels should be measured to at least an
accuracy of 1 percent of the initial water-level change.  For
moderately permeable materials, time should be measured with
an accuracy of fractions of minutes, and for more permeable
materials, the time should be measured in terms of seconds or
fractions of seconds.  The latter may require the use of  a
rapid-response, pressure transducer and recorder system.

Data analysis errors. The type curve procedure requires

matching the data to one of a family of type curves, described
by the parameter ex, which is a measure of the storage in  the
well bore and aquifer.  Papadopulos and others (1973) show that
an error of two orders of magnitude in the selection of oc would
result in an error of less than 30 percent in the value of
transmissivity determined.  Assuming no error in determining
the thickness of the zone tested, this is equivalent to a 30
percent error in the hydraulic conductivity.

1.4.2    Methods For Extremely Tight Formations Under
         Confined Conditions
1.4.2.1  Applicability.  This test is applicable to materials
that have low to extremely low permeability'such as silts,

                              1-15

-------
clays, shales, and  indurated  lithologic units.   The test has
been used to determine  hydraulic  conductivities of shales of as
low as 10~10 cm/sec.

1.4.2.2  Procedures.  The  test  described by Bredehoeft and
Papadopulos  (1980)  and  modified by  Neuzil (1982)  is conducted
by pressurizing suddenly a packed off  zone  in a portion of a
borehole or well.   The  test is  conducted using  a system such as
Shown in Figure 1.4-2.  The  system is filled with water to a level
assumed to be equal  to  the prevailing  water level.   This step
is required if sufficiently large times have not elapsed since
the drilling of the  well to allow full recovery of water
levels.  A pressure  transducer  and  recorder are used to monitor
pressure changes  in  the system  for  a period prior to the test
to obtain pressure  trends  preceding the test.   The system is
pressurized by addition of a  known  volume of water with a
high-pressure pump.  The valve  is shut and  the  pressure decay
is monitored.  Neuzil1s modification uses two packers  with a
pressure transducer  below  the bottom packer to  measure the
pressure change in  the  cavity and one  between the two  packers
to monitor any pressure change  caused  by leakage around the
bottom packer.

1.4.2.3  Calculations.  The modified slug test  as developed by
Bredehoeft and Papadopulos (1980) considered compress'ive
storage of water  in  the borehole.  These authors considered
that the volume of  the  packed-off borehole  did  not change
                              1-16

-------
Pressure Gage Q
System Filled
with Water !
|
;
, 	 — Formation^j-- 	 [•
:- 	 -fl



System Filled
jwith Water
Open Hole
"'Packer-
3F-— —
3- 	
Interval to-
be Tested —
:_ 	 J& 	 _- :- 	
                                                       Pump
                (a)
                              (b)
Figure 1.4-2 —
Schematic diagram  for pressurized slug
test method in unconsolidated  (a)  and
consolidated  (b) materials.  Source:
Papadopulos and Bredehoeft,  1980.
                          1-17

-------
during the  test  and  that  all  compressive storage resulted in
compression of water under  the  pressure pulse.   Neuzil {1982)
demonstrated  that  under some  test conditions this is .not a
valid assumption.  The computational  procedure  is the same in
either case.  Data is plotted in  the  same manner as for the
conventional  slug  test and  type curves  are used from either
Lohman (1972, Plate  2) or plotted from  data given in Table 1.4-1
as described  in  Section 1.1.1.3.   The value of  time (t) and
dimensionless time,  (0),  are  determined in the  same manner as
for the conventional tests.   If compression of  water only is
considered, transmissivity  is computed  by replacing rc2 by the
quantity  (Vw  CwP gA) in  Equation 2.
             8(VW Cy pg/ir)2
(2)
where
       Vw  is  the volume  of  water  in  the  packed-off cavity,  L^;
       •GW  is  the compressibility  of  water,  LT2n~l,
        p  is  the density of water ML~3;  and
        g  is  the accleration  of gravity, LT~2.

If the compressive  storage  is altered  by changing the volume of
the packed-off cavity  (V),  then the  combined compressibility of
the water  and the expansion of the cavity (Co)  is used.   Co is
computed by measuring  the volume  of  water injected during
                              1-18

-------
pressurization  (AV) and  the  pressure  change AP  for  the
pressurization:
          C0  =
               VAP
(Neuzil, 1982 /  page  440).   Use of Co requires an accurate method
of metering  the  volume  of  water injected and the volume of the
cavity.

1.4.2.4  Sources of  Error.   The types of errors in this method
                           t
are the same as  those for  the  conventional slug test.  Errors
may also arise  by inaccurate determination of the cavity volume
and volume of water  injected.   An additional assumption that is
required for this method  is  that the hydraulic properties of
the interval tested  remain constant throughout the test.  This
assumption can  best  be  satisfied by limiting the initial
pressure change  to a value only sufficiently large enough to
be measured  (Bredehoeft and  Papadopulos, 1980).

1.4.3    Methods for Moderately Permeable. Materials Under
         Unconfined  Conditions
1.4.3.1  Applicability.  This  method is applicable to wells
that fully or partially penetrate the interval of interest
(Figure 1.4-3).  The hydraulic conductivity determined will be
principally  the  value in  the horizontal direction (Bouwer and
Rice, 1976).

1.4.3.2  Procedures.  A general method for testing cased wells
that partly  or  fully penetrate aquifers that have a water table
                              1-19

-------
                 WELL CASING
    WELLSEAI
       Lw
   7
    L*
L_L
*l
vei
1
     GRAVEL PACK
                                  Lw
                                  L*
                                          k
                                                       Lw
                                                                        STATIC WATER
                                                                          LEVEL
                                                    IMPENETRABLE STRATUM ''
' *Wr»\ '^        11 • (« . * *

     <•> CASED WITH SCREEN
                        (b) CASED. NO SCREEN, NO
                           CAVITY ENLARGEMENT
                                     (c) OPEN BOREHOLE
   Figure  1.4-3  —Variable definitions for  slug tests  in
                  unconfined   materials. Cased wells are
                  open at the bottom.
                                     1-20

-------
as the upper  boundary of  the zone to be tested was .developed by


Bouwer and  Rice  (1976).   The geometry and dimensions that are


required  to be known  for  the method  are shown in Figure 1.4-3.  The


test is accomplished  by effecting a  sudden change in fluid


potential in  the well by  withdrawal  of either a bailer or sub-


mersed float  as discussed in Section 1.4.1.2.  Water-level


changes can be monitored  with either a pressure transducer and


recorder, a wetted  steel  tape,  or an electric water-level


sounder.  For highly  permeable  formations, a rapid-response


transducer  and recorder system  is required.   The resolution of


the transducer should be  about  0.01  m.




1.4.3.3   Calculations.  The  hydraulic conductivity is calcu-


lated using the following equation in the notation of this


report, taken from  Bouwer and Rice (1976)
                2     ~
             rc  In  R/r    ,_  ,_
         K = 	__*  ln  ±2  ,                           (3)
                2  Let          Y
where rc, rw,  Le,  t,  Y,  and  K have been previously defined or


are defined  in Figure 1.4-2(a).  y  i« the value of Y immediately

after withdrawal of  the  slug of water.   The term R is an effec-


tive radius  that is  computed using the  following equation given


by Bouwer and  Rice (1976).
        R      1     1.1     . A  +  B  ln[(H0-Lw)/rw]   ~1
     ln «_  =   t 	  + 	 }   t       (4)

        rw      In  (Lw/rw           (Le/rw)
                              1-21

-------
for wells  that  do  not  fully penetrate the aquifer,   if the quan-
tity  (H0-Lw)/rw) is  larger  than 6,  a value of 6 should be used.

For wells  that  completely penetrate the aquifer, the .following
equation is  used:
                                       _1
      In —  »  ( 	i^i	  + —£— )   ,                  (5)
         rw      In  (Lw/rw)     Le/rw

(Bouwer, 1976).  The values of the  constants A, B,  and C are
given by Figure 1.4-4 (Bouwer and Rice,  1976).
For both cases, straight-line portions  of plots of  the
logarithm  of Y  or  YO/Y against time- should be used  to determine
the slope, In Yo/Y
              t
Additional methods for tests under  unconfined conditions are
summarized by Bower  (1976)  on pages 117-122.  These methods are
modifications of the cased-well method  described above that
apply either to an uncased  borehole or  to a well or piezometer
in which the diameter  of  the casing and the borehole are the
same  (Figures i.4-3(b) and  (c).
1.4.3.4  Sources of  Error.   The method  assumes that flow of
water from above is  negligible.   If this assumption cannot be
met,  the conductivities may be in error.  Sufficient flow from
the unsaturated zone by drainage would  result in a  high conduc-
tivity value.   Errors  caused by measuring water levels and
recording  time  are similar  to those discussed in Sections
1.4.1.4 and  1.4.2.4.
                              1-22

-------
   14
 A
and
 C
   12
   10
   6
         X I , I . I I .1 I J_l
                        .t.l UP
                                                       B
                10
90  100
500  1000
5000
  Figure 1.4-4 —Curves defining  coefficients A,  B,
               and C in equations 13 and 14 as
               a function of the ratio L/rw.
               Source: Bower and Rice, 1976.
                        1-23

-------
1.5   MULTIPLE WELL TESTS






Hydraulic conductivity can also be determined by conventional



pumping tests in which water is continuously withdrawn or



injected using one well, and the water-level response is



measured over time in or near more observation wells.  These



methods generally test larger portions of aquifers than the



single well test discussed in Section 1.4.  For some cir-



cumstances these tests may be appropriate in obtaining data to



use in satisfying requirements of Part 264 Subpart F.  However,



the large possibility for non-uniqueness in interpretation,



problems involved in pumping contaminated fluids, and the



expense of conducting such tests generally preclude their use



in problems of contaminant hydrogeology.  The following



references give excellent discussions of the design and



interpretation of these tests:  Lohman (1972),  Stallman (1971),



and Walton (1970)..





1.6   FRACTURED MEDIA





Determining the hydraulic properties of fractured media is a



difficult process.  Darcy's Law is not strictly applicable



to flow through fractures.  However, it can be applied empirically



to large bodies of fractured rock if the fractures are spaced



closely enough so that the rock acts hydraulically in a manner



similar to granular porous media.  For rocks with low fracture



density, analyzing flow in individual fissures may be necessary.



If these fissures are wide, flow may not be laminar and Darcy's
                              1-24

-------
Law does not apply.
The upper limit of Darcy's Law can be determined with the help

of the Reynold's number, Re, defined for porous media as


                       Re =  /?vd
where  j& ~ density

       JU- - viscosity

        v = specific discharge

        d = a representative length dimension for the porous
            medium (e.g., mean pore dimension, mean grain
            diameter,' etc. )


It is widely used to distinguish between laminar flow occuring

at low velocities and turbulent flow at higher velocities.

Darcy's Law generally remains valid for Re values between 1 and

10.  In wide fractures, Re can exceed this limit, making flow

analysis very difficult.


Furthermore, since fractured rock has low porosity, expansion

and contraction due to hydraulic and pressure head stress

affects the size of the fractures.  Thus K becomes a function

of this stress, and is no longer constant.


Finally,  determining fractured flow is difficult because the

orientation of fractures and density of their spacings in

different directions can cause anisotropy and trending heterogeneity

for K values.   With all of these difficulties, a methodology

for estimating K in fractured media is beyond the scope of this

document.  The investigator should consult Sowers (1981) for

guidance in analyzing flow through fractured media.


                              1-25

-------
               DETERMINATION OF EFFECTIVE POROSITY





SECTION 2.0



     Calculation of time of travel (TOT) of ground water to



evaluate the vulnerability of the saturated zone requires data



on effective porosity, ne/ with respect to flow through the



porous media.  Effective porosity is usually less than total



porosity in that only the interconnected pore space through



which fluid flow occurs is of interest.  Effective porosity



does not take into consideration the pore space in which fluid



is practically immobile.  Effective 'porosity is less than total



porosity in fine textured medium where adhesion (i.e., the



attraction of molecules of fluid to adjacent solid surfaces of



the porous matrix) is important or when the porous matrix includes



a large portion of dead-end pores.  (Bear, 1979)





2.1  Specific Yield in the Unconfined Aquifer



     Ground-watereand drainage engineers often equate the term



effective porosity with the specific yield,  Sy,  when referring to



an unconfined aquifer where the water table is at depth equal to



several times the height of the capillary fringe.   In these cases,



the term drainable porosity is also used.



     Specific yield, Sy, is defined as the volume of water that



an unconfined aquifer releases from storage per unit decline in



the water table.  As discussed by Freeze & Cherry (1979), the



idea of specific yield is best visualized with reference to the



saturated-unsaturated interaction it represents.  Figure 2.0-1
                               2-1

-------
to
I
                           XT7I
    Moisture content, Q

                       n
                      /77/////////////'
///////////////////////////////////////
                Figure 2.0-1  concept of specific yield viewed  in terms of the unsaturated moisture profiles

                            above the water table.  (Freeze & Cherry, 1979)

-------
                                                    OSIVER POLICY DIRECTIVE KQ,
shows the water-table position and  the  vertical  profile  of  moisture
                                                fc
content vs. depth in the unsaturated  zone  at  two times, ~ti~a~nd

t2-  The cross hatched area represents  the volume of water  released

from storage in a volume of unit cross  section.   If the  water-table

drop represents a unit decline, the cross  hatched area represents

the specific yield, Sy.

     The volume of water retained in  an aquifer  per unit area and

unit decline of the water table is  called  specific retention, Sr.

In a homogeneous isotropic soil with  a  sufficiently deep water

table, Sy + Sr = n when rt is the total  porosity  and specific

retention is identical to the field capacity  of  the soil.   Under

such conditions, Figure 2.0-2 shows the relationship between

specific yield and specific retention for  various soils.  (Bear,

1979)

     Laboratory values of specific  yield   usually differ from

those taken in the field due to the effects of

     0 aquifer stratification,

     0 slow drainage of materials above the water table,

     0 air entrapment in the zone below the water table,

     0 water table positions,

     * the rate of change of the water  table  elevation.

Actual yields from field tests are  reduced up to one-third  of

laboratory values of Sy. Therefore, McWhorter and Sunada (1977)

differentiate between laboratory and  field values by defining a

bulk parameter, apparent specific yield, Sya, that incorporates

these field influences. Because apparent specific yield  depends
                               2-3

-------
                             Well-sorted material	
                                 Average material
   60%

   50%

   40%


   30%

   20%

   10%


    0%
            10~3
            Clay
io-2
  Silt
io-1    10°
   Sand
  IO1
Gravel
                        Median grain size (mm)
IO2
Cobbles
Figure 2.0-2 Relationship between specific yi$ld and grain size (from Conkllng et, al., 193f,
         as modified by Davis and DeWiest, 1966)  Bear,  1979

-------
on more than just the physical properties of porous solids,



values of apparent specific yield may bear little or no relation



to the specific yield.  Field determination of apparent specific



yield as defined above can be made from analysis of aquifer test



data using the Theis solution or the Jacob method (when applicable)



as described by McWhorter & Sunada.  Field determined values of



apparent specific yields are preferred over laboratory values



for determining the TOTiQO since they provide a more accurate



representation of the drainage porosity of the water-table aquifer.





2.2  Confined Aquifers



     Time of travel calculations as discussed in this document



concern ground-water flow along a 100 foot flow line originating



at the base of the hazardous waste unit where ground-water move-



ment through saturated zones usually occurs under phreatic



(unconfined) conditions.  However some flow lines may originate



or travel through a confined aquifer.  Determination of



effective porosity for confined aquifers is rather different



than for an unconfined aquifer.



     First, the capacity of confined aquifers to release water



from storage is markedly different from that of unconfined aquifers



The storage capacity of water-table aquifers, termed specific



yield, is representative of the effective porosity of the porous



media under homogeneous, isotropic conditions (Section 2.1).



As discussed by Freeze & Cherry, water released from storage in a



confined aquifer, termed storativity, is not derived from drainage
                               2-5

-------
of the voids as is the case in unconfirmed aquifers.  Rather, it



is a function of the porosity of the aquifer material, the



secondary effects of water expansion and overburden stress, and



aquifer geometry.  Therefore, storativity values for confined



aquifers should not be used as default values for effective



porosity.



     Effective porosity for a confined aquifer may be best



approximated by laboratory tests run on samples taken from



the site, in order to bypass the secondary effects incorporated



into storativity values, yet still yield an effective porosity



that is as site-specific as possible.





2.3  Tabulated Values of Effective Porosity



     Selection of tabulated values of effective porosity based on



soil texture classification (Table 3.2-2 in Guidance Criteria



for Identifying Areas of Vulnerable Hydrogeology :  RCRA Statutory



Interpretive Guidance, June 1986) must consider site-specific



conditions when evaluating the vulnerability of the ground water



to waste constituents.  The tabulated values are valid approximations



of effective porosity only in homogeneous geologic units composed



of relatively coarse materials in which the water table is at a



sufficient depth so as to eliminate any influence from the



capillary fringe.  For example,  recent studies indicate that the
water in some unweathered glacial tills in connate water



from the time of deposition (Barari and Hedges, 1985; Bradbury



et al., 1985).  This suggests that ground-water flow in some



materials may be very slow or nonexistent.  The tabulated
                               2-6

-------
values should be reduced up to one-third to incorporate the



influence of factors such as air entrapped near the water table,



stratification of materials above the water table, water table



position and the rate of change of the water table elevation



(McWhorter and Sunada, 1977).



     For confined aquifers where storativity values are inaccurate,



and for tight formations where specific yield values are unobtain-



able from field tests, tabulated values may be used as guidelines



for estimating effective porosity.
                               2-7

-------
                  FACTORS AFFECTING CHANGES IN
                       HYDRAULIC GRADIENT
SECTION 3.0

     Accurate determination of vertical and horizontal hydraulic

gradients is very important in characterizing a site's flow

regime.  Overall characterization of hydraulic gradient (i) should

be done by using nested piezometers that are screened in the same

geologic unit, as discussed in Section 3.0 of the main text, in

Appendix B, and in the RCRA Technical Enforcement Guidance Document

U.S.EPA (Draft) 1985, (TEGD).  Because methods for determining

hydraulic gradient are well-documented, this section will only

discuss factors that influence variations in (i) over time.

     Seasonal, temporal, and artificially-induced variations in

ground-water flow and in corresponding hydraulic gradients

should be evaluated with respect to the resultant effect on TOT

calculation.  The direction and rate of ground-water flow and

the hydraulic gradient,  can be influenced by one or more of the

following external factors:

     -  well pumping

        tidal processes and fluctuation

        intermittent natural variation in river stage (e.g., bank
        storage)

     -  artificial recharge

        natural seasonal variations

        construction activities or change in land use

     Off-site or on-site well pumping may effect both the rate

and direction of ground-water flow in time-continuous or
                              3-1

-------
discontinuous patterns.  Well water-level measurements must be



frequent enough to detect such water use patterns.



     As discussed in the TEGD, natural processes such as



riverine, estuarine, or marine tidal movement may result in



variations of well water levels and/or ground-water quality.



Ground-water/stream flow interactions often influence the



hydraulic gradient of the ground water in the area adjacent to



the stream.  An increase in river stage may induce flow into



stream banks creating a temporary reversal of ground-water flow



as shown in Figure 3.0-1.  As the river stage declines, the



flow is reversed.  Transitional patterns that may shift ground-



water flow directions must be evaluated with respect to the



effect on the vulnerability of the aquifer.



     Short-term recharge patterns may affect ground-water flow



patterns that are markedly different from ground-water flow



patterns from seasonal averages.  Selection of the hydraulic



gradient term in the time of travel calculation should incorporate



any variation in ground-water flow that may result from seasonal



fluctuations.  Short-term fluctuations in the ground-water flow



pattern that result from dewatering due to construction, changes



in land use, or artificial recharge should also be evaluated in



the determination of the hydraulic gradient (see Figure 3.0-2).



     The frequency of well water-level measurements from which



hydraulic gradients are determined will depend upon the nature



of the particular processes influencing ground-water flow at



the site.  Well water-level measurements taken on a monthly



basis may be adequate to characterize natural seasonal variations.





                              3-2

-------
U)
I
                                 TEMPORARY REVERSAL OF GROUND-WATER FLOW DUE TO
                                             FLOODING OF A RIVER OR STREAM
Tempo>»ry
leveiial ol
9>ound«vaiei How  .
                                                                                                      m
                   Figure 3.0-1  Diagram of how temporal changes in hydraulic gradient affect  the
                               flow paths of groundwater.

-------
u>
               Zone of aeration
                and treatment
                                 Infiltration
                                                      Refuse)

                                                      Percolation through
                                                       unsaturated zone
                   Recharge mound
^^^
                                                                                       Original water table
                 Figure 3.0-2.
              Illustration of how artificial recharge through an unsaturated zone from
              a waste unit causes a recharge mound which changes the  initial head in
              the saturated zone.

-------
However, some daily water-level measurements may be required to



evaluate the influence of external factors such as well pumping,



dewatering due to construction, or artificial recharge.  Riverine,



estuarine, or marine tidal influences may affect ground-water



flow patterns over a shorter time period making hourly or



continuous water level monitoring desirable.  Continuous water



level monitoring should be performed until a pattern of general



water level fluctuation is determined for the site.  Minimum



and maximum fluctuations of water level dependent upon site



conditions (i.e., external factors affecting water level and/or



natural factors such as tidal influences) should be carefully



considered.



     Variations in hydraulic gradient determined from ground-



water level monitoring will result in a range of ground-water



flow velocities and possible variaton of flow direction.  Flow



nets should be updated to reflect hydraulic gradient fluctuations



in order to evaluate a 'worst-case' 100-foot flow line.  Time



of travel calculations should be made over the range of ground-



water velocities to account for the effect of seasonal and temporal



factors on the ground-water flow system. For example,  Figure



3.0-3 illustrates that during a low water table, the 'worst-case'



100 foot flow line would travel down into the aquifer.  However,



during a season with high precipitation, another principal flow



line would appear, moving horizontally out along a near surface



'basement-seepage' pathway. Further evaluation would be necessary



in this case to calculate which flow path would represent the



fastest TOT.






                              3-5

-------
                                                    Precipitation

                                             \y      Y     Y     Y     Y
                      SEASONAL HIGH
                      WATER.TABLE
CO
            SEASONAL LOW
             WATER TABLE
                                                                  ^Groundwater zone
                                                                      contaminated by  leachate
           Figure 3.0-3  Diagram of mounding  in the saturated zone.  Mounding within the waste unit causes
                        an increase in hydraulic gradient, providing a greater driving force for the
                        contaminant plume.   Also note that changes in the seasonal precipitation chance  '
                        the water table elevation, opening a new shallow migration path alone the more
                        permeable upper soil level.

-------
     The initial head as a result of infiltration through a



landfill cover and the build up of leachate on the bottom liner



must be determined.  The Hydrologic Evaluation of Land Performance



(HELP) Model can be used to estimate water movement across, into,



through, and out of landfills for a wide variety of landfill



designs.  In the context of evaluating vulnerability as a



function of hydraulic gradient, the build up of leachate on or



beneath the landfill liner and its related impact on flow



velocity is of concern.  Section 5 of the U.S. EPA Draft Background



Document entitled, Technical Support for Development and Analysis



of Hazardous Waste Disposal Regulations, March 1986, addresses



the use of the HELP model in estimating head at a landfill



liner.  The HELP model expresses leachate head on the liner in



inches at designated time intervals.  The calculation techniques



and inherent assumptions associated with the HELP model are



discussed in the referenced Draft Background document.  The



major assumption impacting the accuracy of leachate head is that



of fully saturated conditions within the liner.  This assumption



must be considered in determining hydraulic gradient for



calculating flow velocity.
                              3-7

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                          REFERENCES
SECTION 4.0
4.1 References for Section 1.0

Acker, W. L., Ill, Basic Procedures for Soil Sampling and Core
     Drilling, Acker Drill Co., 246 p., 1974.


Bear, J., Dynamics of Fluids in Porous Media, American Elsevier,
     764 p., 1972.


Bouwer, H., Groundwater Hydrology, McGraw Hill, 480 p., 1978.


Bouwer, H., and R. C. Rice, "A slug test for determining hydraulic
     conductivity of unconfined aquifers with completely or
     partially penetrating wells", Water Resources Research,
     12, p. 423-428, 1976.


Bredehoeft, J. D., and S. S. Papadopulos, "A method for deter-
     mining the hydraulic properties of tight formations",
     Water Resources Research, 16, p.233-233, 1980.


Cooper, H. H., J. D. Bredehoeft, and I. S. Papadopulos,
     "Response of a finite diameter well to an instantaneous
     charge of water", Water Resources Research, 3, p. 263-269,
     1967.
Freeze, R.A., and J.A. Cherry, Groundwater, Prentice Hall,
     604 p.,  1979.


Johnson, E. E., Inc., Groundwater and Wells, Johnson Division,
     UOP, 440 P., 1975.
Lohman, S.W., Groundwater Hydraulics, U.S. Geological Survey
     Professional Paper 708,70 p., 1972.


Neuzil, C.E., "On conducting the modified  'slug' test in tight
     formations", Water Resources Research, vol. 18, no.2,
     pp. 439-441, 1982.
                              4-1

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Papadopulos, S. S., J. D. Bredehoeft, and H. H. Cooper, Jr.,  "On
     the analysis of  'slug test' data", Water Resources Research,
     9, p. 1087-1089, 1973.


Sowers, G.F., "Rock permeability or hydraulic conductivity -  an
     overview", ir\ Permeability and Groundwater Transport, ed.
     T.F. Zinunie and Co., O. Riggs, ASTM Special Technical
     Publication 746, 1981.
Stallman, R. W., Aquifer-Test Design, Observation and Data
     Analysis, TWRI, Chap. Bl, Book 3, U.S. Geological Survey,
     U.S. Govt. Printing Office, Washington, D.C., 1971.


U.S. EPA, Test Methods for Evaluating Solid Waste;  Physical/
     Chemical Methods? Test Method 9100:  Methods for Determining
     Saturated Hydraulic Conductivity and Saturated Leachate
     Conductivity; OSW, SW-846.


Walton, W. C., Groundwater Resource Evaluation, McGraw Hill,
     664 p., 1970.


4.2 References for Section 2.0
Barari, A. and L.S. Hedges, "Movement of water glacial till",
     Proceedings of the 17th International Congress of the
     International Association of Hydrogeologists, pp.129-134,1985,


Bear, Jacob; Hydraulics of Groundwater, McGraw-Hill, Inc.., 1979


Bear, Jacob; Dynamics of Fluids in Porous Media, American Elsevier
     Publishing Company, Inc., 1972


Bradbury, K.R., D.S. desaulniers, D.E. Connell, and R.G. Hennings,
     "Groundwater movement through clayey till: Northwestern
     Wisconsin, U.S.A.", Proceedings of the 17th International
     Congress of the International Association of Hydrogeologists,
     pp. 405-416, 1985.


Freeze, R. Alen and Cherry, John A., Groundwater, Prentice-Hall,
Inc., 1979


McWhorter, David B. and Sunada, Daniel K., Ground-Water Hydrology
and Hydraulics, Water Resource Publications, 1977
                              4-2

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                                                Q5WEH POLICY DlRECTWt
                                              9472 • 00
4.3 References for Section 3.0
GCA Technology Division, Inc., Technical  Support  for  Development
and Analysis of Hazardous Waste Disposal  Regulations,  Draft
Background Document, March 1986.
U.S.EPA, RCRA Ground-Water Technical Enforcement Guidance  Document
(Draft), 1985.  Contact OWPE of the Office of Solid Waste  and
Emergency for information on final publication date and availability


U.S.EPA, The Hydrologic Evaluation of Landfill Peformance  (HELP)
Model, Volume 1.User's Guide for Version 1,Technical Resource
Document for Public Comment.
                              4-3

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