OOOD82001
   TD367
   .R37
   1982y
   vol.1
                                     DRAFT
                   RCRA   GUIDANCE    DOCUMENT
                     SURFACE    IMPOUNDMENTS
          LINER   SYSTEMS,   FINAL   COVER,    AND
                        FREEBOARD    CONTROL
                         [TO BE  USED WITH RCRA REGULATIONS

             SECTIONS 264.221U)  and 
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               TABLE   OF   CONTENTS


A.   Purpose and Use

B.   Liner System Function, Components, and Life

     1.   The Regulations
     2.   Guidance
     3.   Discussion

C.   Leak Detection, Collection, and Removal Systems

     1.   The Regulations
     2.   Guidance
     3.   Discussion

D.   Liner Specifications

     1.   The Regulations
     2.   Guidance
     3.   Discussion                                                      ,
                                                                          *»
E.   Cap (Final Cover) Design

     1.   The Regulations
     2.   Guidance
     3,   Discussion

F.   Freeboard Control

     1.   The Regulations
     2.   Guidance
     3.   Discussion

Appendices

     A.   Hydraulic Conductivity Test Method
     B.   Compatibility Test Method

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A.   Purpose and Use
     This guidance document presents surface impoundment
design specifications which the Agency believes comply with
the Design and Operating Requirements of §§264.221(a) and (c),
and 264.222(a), and the Closure Requirements of §264.228(a)  of
the RCRA surface impoundment regulations (40 CFR 	).
These regulations have been formulated with the goal of elimia-
ting the escape of hazardous waste and hazardous constituents
from surface impoundments for all time to the extent practical.
Given that few things work perfectly, or work for all time,
absolute prevention of escape for all time is probably not
realistic.  However, the regulations require surface impoundments
to come as close to the containment ideal as possible.  In
actual practice, the Agency believes containment is practical
during the operating life of the impoundment in the absence of
damage to the containment system.  In the long run, however,
in the distant years after closure of disposal impoundments,
minimization of leachate formation and escape is the best
that current technology can practically achieve.
     For most impoundments, the regulations provide that liner
systems be installed that are capable of preventing release  of
hazardous wastes and their derivatives during operating life.  At
closure, the wastes and contaminated liners, equipment, and  sub-
soils must either be removed or a cap must be installed that is
designed to minimize release of pollutants into the distant
future.  To protect surface waters, a surface impoundment must
be designed, constructed, and operated so that it does not
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overflow.  The closure rules essentially eliminate the potential
for significant overflow to surface waters after closure.
     To provide flexibility, the design and operating character-
istics required are expressed in terms of performance standards
for system components as a whole.  Optimally, these standards
would contain numeric limits to the performance required of
each system component, and most, but not all of the currently
promulgated standards are expressed in numeric terms.  For
others, minimum specifications are not included.  For example,
though a final cap must be incorporated,  unless the waste is
removed at closure, the required capabilities of that system are
currently expressed in general terms, specifically "Provide
long-term minimization of the migration of liquids".   The
Agency intends to augment the general statements currently in
the regulations by applying numeric limits to the performance
required of each component.  But, there will still be substantial
flexibility in designing facilities to meet the standard and
substantial uncertainty involved in judging whether a given
design will, in fact, achieve the performance level prescribed.
     This document is designed to provide specific guidance on
designs the Agency believes accomplish the performance state-
ments in the regulations.  As a result, permit applicants
designing their facilities in accordance with the specifications
contained herein,  will be considered in compliance with §§264.221(a)
and (c), 264.222(a)(3), and 264.228(a).  This provides certainty
to the permitting  process because, if these specifications and
procedures are followed, a draft permit will be issued.  (Final
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permits cannot be issued until input from the public participa-



tion process is evaluated.)



     The Agency wishes to emphasize that the specifications



contained herein are guidance/ not regulations.  The Agency is



not requiring, and does not intend, that all facilities be built



in this way.  On the contrary, the Agency believes there are



many designs which can be acceptably used, depending on waste



characteristics and location.   Owners or operators wishing to



use a different design, but one that contains the basic design



components of §§264.221(a) and (c), 264.222(a), and 264.228(a),



i.e., liners, overtopping controls, and caps (if disposal



units),may demonstrate compliance with the performance require-



ments for the specific components, directly to the permitting



official.  An easy way to demonstrate compliance with the



performance requirements would be to show that the specific



design incorporated at a particular unit provides the same



level of performance as would the design incorporated in this



guidance under similar circumstances (waste characteristics,



location, rainfall, etc.).  For example, the specifications



for the final cover in this guidance call for a final slope of



between three and five percent to promote drainage without



causing erosion.  To demonstrate the acceptability of a greater



slope, the applicant could attempt to show that because of the



materials used, perhaps in combination with other design



features, a greater slope will result in no more erosion than



would be the case utilizing the slope specifications contained



herein.  The Agency will accept convincing demonstrations of



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equivalency of performance to the specifications in this



guidance as adequate demonstration of compliance with the



performance standards of §§264.221(a) and (c) and 264.228(a).



     This document contains only initial guidance—it will be



significantly expanded over time to include additional designs



and specifications which the Agency believes acceptably comply



with the performance requirements of the regulations.  Since



the Agency can only recommend the liner specifications contained



in this document for installation above the water table, it is



diligently working on similar specifications for location in



saturated soils.  EPA hopes to issue this additional guidance



in the near future.  This document will also be expanded by



incorporating the experience gained in implementing the



performance standards.



     The document is arranged according to the section of the



regulation to which it corresponds.  Those wishing  to send



technical information or suggestions concerning this document



should address them to:  Rod Jenkins, Chief, Land Disposal



Branch, Office of Solid Waste (WH-564), U.S.  Environmental



Protection Agency, 401 M Street,  S.W.,  Washington,  D.C. 20460.



EPA is particularly interested in information and suggestions



concerning the usefulness of the document, expansion of it,



and the effectiveness of the guidance contained in ensuring



compliance with the performance requirements in the regulations.



     EPA is also producing a series of Technical Resource



Documents (TRDs), two of which cover caps and liners, and a third



that covers surface impoundment closure.  The TRDs are designed



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to comprehensively but concisely present the sum total of  the



body of information and experience gained by the Agency over



the years on a given topic.  As such, they contain factual



summaries concerning the experiences and effectiveness of



design alternatives, covering what has been found not to work



as well as what has been found to be effective.  They contain



no policy-related direction.  The TRDs can be considered as



technical background or development documents supporting these



guidance documents and the regulations.  Based partially on



the information contained in the TRD's, the Ajency made the



policy decisions which resulted in the regulations and these



guidance documents.  TRD's corresponding to the guidance in



this document are:



     (1)  Evaluating Cover Systems for Solid and Hazardous Waste



(SW-867) NTIS Publication No. PB-81-166-340.



     (2)  Lining of Waste Impoundment and Disposal Facilities



(SW-870) NTIS Publication No. PB-81-166-365.



     (3)  Closure of Hazardous Waste Surface Impoundments



(SW-873) NTIS Publication No. PB-81-166-894.



These documents can be obtained from the National Technical



Information Service, U.S. Department of Commerce, Springfield,



Virginia 22161.  The Agency plans to publish amended versions



of these documents in the fall of 1982.



B.   Liner System Function, Components, and Life



     1.    The Regulations



     The regulations require the system to function through



scheduled closure and to consist of at least one liner designed



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and constructed to prevent transmission of liquids through  it.
In the case of disposal impoundments (i.e., where the waste will
be left in place at closure), the liner must be essentially
impermeable to liquids, allowing no more than de minimum infiltration
of liquids into the liner itself.
     2.   Guidance
     (a)  Liner systems should be constructed wholly above  the
seasonal high water table, i.e., in the unsaturated soil.
     (b)  Liner systems for storage or treatment impoundments
where the waste will be removed at closure should consist of
a single soil (clay) or synthetic liner, as a minimum.
     (c)  Liner systems for disposal impoundments where the
waste will remain at closure should consist of a single synthetic
liner, as a minimum.
     (d)  Where a synthetic liner is used  in any surface impound-
ment which will not complete closure for 30 or more years
after first placement of wastes, the underliner system should
consist of the following as a minimum:
     (i)  A primary synthetic liner; and
     (ii) A secondary soil liner (e.g., clay).
     3.   Discussion
     In developing the designs contained in this guidance,  the
Agency"has attempted to come as close as possible to complete
containment for as long as the impoundment is in operation.
However, the Agency also used, as an overriding criterion,
that the designs developed be based on conventional technology,
utilizing readily available equipment and materials, at practical
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     Essentially complete but temporal containment is practical



using the synthetic liners developed over recent years.  However,



experience with synthetic liners in contact with chemicals is



relatively recent.   As a result, EPA has no experience base



from which to predict the life of these materials.  However,



predictions based on chemistry,  and limited recent real world



experience are sufficient to convince the Agency that with proper



selection for resistance to chemicals in the waste and proper



design and installation (tight seams and no tears), containment



for at least 30 years is practical, utilizing a single synthetic



liner (some believe that such liners will last in excess of



100 years).  Therefore, a single synthetic liner system is



described for impoundments which will be closed in less than



30 years.  Some surface impoundments, however, are designed



to function almost perpetually.   While the regulations require



a prediction that the synthetic  liner will last as long as the



projected life of the impoundment, regardless of how long that



is, there is no historic proof that such liners will, in fact,



function into the distant future.  Therefore, if final closure



is not scheduled for 30 years or more, a double liner system



incorporating a top synthetic liner and a secondary clay liner



is recommended.  The secondary soil liner functions as a backup



to the synthetic primary liner,  taking over the task of minimizing



liquid transmission when and if  the primary liner deteriorates.



     Some soil materials, typically those classified as clays,



can be deposited and compacted to produce a liner system of very



low permeability.  Movement of liquids through well constructed

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clay liners is very slow as long as the structure of the liner
is not affected by the waste materials or is not otherwise
damaged.  As a result, when functioning properly, the release
of liquid-containing hazardous constituents to the ground water
and surrounding soils, is effectively minimized (but not pre-
vented) by the secondary clay liner.  Thus, absolute preven-
tion of escape of liquid wastes and pollutants through the
liner system during the life of very long lived surface impound-
ments may not be fully achievable,  in those cases where the
primary synthetic liner deteriorates, though the use of the
secondary clay liner should keep the rate of escape to very
low levels.
     Storage impoundments are a special case, however.  Storage
impoundments must be closed by removing the wastes, contaminated
liners, and equipment at closure.  Should there be any leakage
through the liner during operation of a storage impoundment,
the contaminated soil must either be removed or decontaminated
as well.  Since removing and decontaminating soil can be an
expensive process, it is important to owners and operators of
storage impoundments that liner systems not leak during the
life of the impoundment.  The Agency is convinced that synthetic
liners will readily achieve this goal, assuming the liner is
not attacked chemically or damaged physically, and assuming
that site life is 30 years or less.  The Agency also believes
that adequate protection can be achieved by use of a single
clay liner of sufficient thickness and impermeability to
ensure that no waste travels through the liner before closure
when both the waste and the saturated liner are removed.
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Thus, in the Agency's view, for storage impoundments, clay and



synthetic liners can be considered equally protective under most



circumstances.



     For disposal impoundments, where the waste and contaminated



liners will remain after closure, the Agency believes that



synthetic liners are preferable because they constitute a more



efficient barrier to escape of liquid wastes.  As long as they



are  intact, they are essentially 100 percent effective as a



barrier.  If the synthetic liner remains intact through closure,



when the cap functions to greatly reduce leachate generation,



then little, if any, pollutants should have exfiltrated to the




surrounding soil.  (The Agency realizes that very small amounts



of liquids may enter the structure of synthetic membranes



causing them to swell, but the amount is truly negligible and



leads to no future ground water contamination.)  Clay liners,



on the other hand, are somewhat permeable.  Some of the liquid



waste will infiltrate the pore structure of the liner and will



be released over time.  In the Agency's view, therefore, a



single clay liner in a disposal impoundment does not fully



prevent release of hazardous waste constituents reaching its



surface during operating life.  It simply reduces the amount



that is released, retards release, and minimizes the rate of



release.  EPA concludes, therefore, that clay liners are not



nearly so effective as synthetics in the near term (at least



30 years).  The Ayency realizes, however, that there is disagree-



ment as to the relative effectiveness of various types of

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liners.  The Agency is, therefore, seeking data and information
concerning:
     (I)  The relative efficiency of synthetic, soil,  and other
          liners in preventing and minimizing the transmission
          of liquids and the release of pollutants;
     (2)  The effective life of various liner designs;
     (3)  The causes of physical and chemical damage to various
          liners and how damage can be avoided;
     (4)  The potential for saturated soil liners to attenuate
          pollutants;
     (5)  The potential for soil liners to release pollutants
          after proper closure has removed liquids from the
          impoundment and reduced the amount of leachate formed;
          and
     (6)  The benefits to be realized and the risks posed by
          various liner designs.
     The designs suggested are specifically recommended for
installation in the unsaturated zone.  The Agency views location
in the ground water as fraught with additional risks and design
difficulties.  This does not mean, however, that the Agency frowns
on such locations; EPA is convinced that given certain hydrcgeo-
logical circumstances and accommodating designs, location in
saturated soils can be environmentally acceptable.  In addition
to the potential for leak detection systems to fill with ground
water, the problems associated with location in the saturated
zone are primarily associated with the external pressure applied
by the saturated earth against the liner system.  This can result
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in damage to the integrity of the liner system and to difficul-



ties in removing wastes at closure.  The former is of real con-



cern to the Agency; the latter would be primarily a nuisance to



the operator at closure.  Depending on the active earth pressure



and the way the surface impoundment is designed and operated,



the force exerted by the liquid contents of the impoundment




may offset the external force exerted by the saturated earth.



If so, no damage to the liner .system would be expected.  Accord-



ingly, the Agency intends to expand the designs in this guidance



to include designs which will effectively minimize the rate of



pollutant release in saturated locations.  In the interim,



those wishing to locate in the saturated zone and whose units



have the basic components specified in the regulations (i.e.,



at least one liner) may be able to readily show that the loca-



tion, design, and operating characteristics of the unit prevent



the migration of pollutants from the unit and that the surface



impoundment will function with an equivalent degree of certainty



(e.g., longevity, damage potential, etc.).  The closer the



actual design is to those in this guidance document, the easier



that demonstration may be to make.  In any event, for now, a



case-by-case demonstration of containment will be necessary



for impoundments located wholly or partially in the saturated



zone.



C.   Leak Detection Systems



     1.   The Regulations



     The regulations do not require a leak detection system.
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However, under the requirements of §264.222 (Double-lined surface



impoundments), owners or operators choosing to install a double



liner system with a leak detection system may be exempted from



the monitoring and other requirements of Subpart F unless and



until contaminated liquid is identified in the leak detection



system.



     2.   Guidance



     Leak detection systems should have:



     (a)  At least a 30 centimeter (12-inch) drainage layer



with a hydraulic conductivity not less than 1 X 10~3 cm/sec



and a minimum slope of 2 percent;



     (b)  A drainage tile system of appropriate size and



spacing and a sump pump or other means to efficiently



conduct liquids.



     3.   Discussion



     The leak detection system is the means by which one can



determine if the primary liner has failed or is leaking.  Under



the operating requirements of §264.222(b), the owner or oper-



ator must then either repair the primary liner or institute



ground-water monitoring, if he is not already doing so.



     There are, of course, many possible designs for detecting



leaks  including the use of advanced instrumentation.  The



system described here is essentially a gravity collection



system, very similar to the leachate collection system for



landfills and waste piles.



     The minimum thickness (30 centimeters or 12 inches) of



the drainage layer is designed to allow sufficient head to



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promote drainage.  The two percent minimum slope is also designed



to promote drainage.  The hydraulic conductivity of not less



than 1 X 10~3 cm/sec was chosen because materials used widely



as drainage media are typically at least that coarse.



     Drainage tile diameter and spacing are important because



they affect the removal of liquids.  The closer the tiles are



together, the more quickly a leak is likely to be detected.



Unlike leachate collection systems for landfills and piles,



however, the primary purpose here is detection of leaks, not



removal.  Thus, tile size and spacing need only be sufficient



for rapid detection of the initial leak and need not be designed



to remove some predetermined volume rate of flow.  The Agency



is therefore not specifying minimum tile spacing or size in



this guidance.  Nevertheless, a reasonably sized drainage system



coupled with an efficient means (such as a sump pump) for



removing collected liquids, will result in capacity to remove



leaking fluids except in the case of severe breaches of the



primary liner.  By so doing, the liquid head on the bottom



liner will remain low providing an extra measure of protection.



EPA believes that a design incorporating 4 in. diameter tiles



on 50 to 200 foot (15 to 60 meter) centers will provide



efficient leak detection and capacity to remove leakage from



minor breaches of the primary liner.



D.   Liner Specifications



     1.   The Regulations



     As discussed in Section B of this guidance, the liner



system must be designed and built to achieve containment of



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fluids during the life of the site thus preventing the escape



of hazardous constituents to surrounding soils and ultimately



to the ground water.  At least one liner must be installed and



the material used must be resistant to the chemicals it will



encounter in the wastes and in the leachate, and be of sufficient



strength to withstand the forces it will encounter during



installation and operation.  In this regard, a base is required



which must provide sufficient support to the liner to prevent



failure.  The liner system must, of course, cover all areas



likely to be exposed to waste and to leachate.



     2.   Guidance



     In Section B of this guidance, the Agency identified the



conditions under which it believes single and double liner



systems are appropriate and the nature of the materials recom-



mended.  Following are liner specifications which the Agency



believes will produce stable construction and which will prevent



the release of hazardous constituents.



     (a)  Synthetic liners should:



     (1)  Consist of at least a 30 mil membrane that is



chemically resistant to the waste managed at  the unit.  In



judging chemical compatibility of wastes and membranes, the



Agency will consider appropriate historical data, demonstrations



involving theoretical chemistry, and actual test data.  Testing



of chemical resistance of liners should be performed using



either the EPA test method attached or an equivalent test



method.
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     (2) Be protected from damage from below the membrane, by



at least 15 centimeters (6 inches) of bedding material no



coarser than Unified Soil Classification System (USCS) sand



(SP) and which is free of rock, fractured stone, debris, cobbles,



rubbish, roots, and sudden changes in grade.  Leak detection



systems, soil  (clay) liners, or natural, in situ soils may



serve as bedding materials when in direct contact with synthetic



liners if they meet the requirements specified herein.



     (3)  Be protected from damage when mechanical equipment



is used to remove sludge or for other reasons, by means of a



minimum of 45 centimeters (18 inches) of protective soil (or the



equivalent) above the top liner.



     (4)  Be protected from damage due to sunlight or wind, where



exposed to the elements, by means of a minimum of 15 centimeters



(6 inches)  of protective soil (or the equivalent) over exposed



surfaces, unless it is known that the liner material used is not



physically or chemically impaired by exposure.



     (b)  Soil liners should:



     (1)  Consist of at least 60 centimeters (24 inches) of



natural or recompacted emplaced soil (e.g., clay) with a sat-



urated hydraulic conductivity not more than 1 X 10""^ cm/sec.



Saturated hydraulic conductivity testing should be conducted



using either the EPA test method attached or an equivalent.
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     (2)  Have a saturated hydraulic conductivity which is

not increased beyond 1 X 10~7 cm/sec as a result of contact

with the waste or leachate generated at the facility.  Testing

of the effect of waste or leachate on soil liner hydraulic

conductivity should be performed using either the EPA test method

attached or an equivalent test method.

     (3)  Have no lenses, cracks, channels, root holes, or

other structural nonuniformities that can increase the nominal

hydraulic conductivity of the liner above 1 X 10~7 cm/sec; and

     (4)  Where recompacted emplaced soil liners are used, be

placed in lifts not exceeding 15 centimeters (6 inches) before

compaction to maximize the effectiveness of compaction.

     (c)  Single soil liners used in  storage or treatment

impoundments from which wastes will be removed at closure should:

     (1)  Have a sufficient thickness of natural or recom-

pacted emplaced soil to provide containment of the waste in

the liner system (i.e., no fluid flow moves beyond the liner)

during the operating life of the unit; the necessary thickness

of soil should be determined by use of the following:
     d = 0.5  I  	tk^  +j/(tk)2 + 4 itkh)
                   e
where:
                                              J
          d = necessary thickness of soil (feet)

          3 = total porosity

          k = hydraulic conductivity (ft/yr)

          h - maximum fluid head on the liner (feet)

          t = facility life from startup through closure (years);


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     (2)  Have a hydraulic conductivity which is not
increased beyond that used in the calculations as a result of
contact with the waste managed at the facility.  Testing of
the effect of leachate on soil liner hydraulic conductivity
should be performed using either the EPA test method attached
or an equivalent test method.
     (3)  Have no lenses, cracks, channels, root holes or other
structural nonuniformities which can act to increase the nominal
hydraulic conductivity above that used in the calculations; and
     (4)  Where recompacted emplaced soil liners are used, be
placed in lifts not exceeding 15 centimeters (6 inches) before
compaction to maximize the effectiveness of compaction.
     3.   Discussion
     EPA believes synthetic liners should be at least 30 mils
thick.   Thinner synthetic membrane liners are known to be
readily damaged.  One of the primary reasons for failure of
synthetic liners, is damage (i.e., punctures, rips, and tears).
Damage occurs during installation or during operation.  With
surface impoundments, punctures occur as a result of the pressure
applied by liquid wastes forcing the membrane against sharp
objects below (rocks, sticks, debris, etc.).  If the impoundment
is a double lined unit with a leak detection system, this is
not usually a problem because the leak detection system normally
provides protection.  However,  even leak detection systems are
sometimes constructed of coarse rock to promote drainage, but
which can damage the liner.  To protect against this, EPA
recommends that a minimum six inch bedding layer be placed
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under the liner.  The bedding layer should consist of materials
which are no coarser than sand (SP) as defined by the Uniform
Soil Classfication System (USCS).  Use of a sand layer is
common practice for protection of membranes and other delicate
materials from damage due to contact with grading equipment and
materials, sharp materials in soil, etc.  The bedding material
need not be a separate layer as natural soils or the leak detec-
tion, collection, and removal systems materials will often meet
the necessary criteria.
     Bedding material is not usually necessary above the liner,
since direct contact is normally with the liquid waste contents
or material settling out of it.  However, the liner can also be
damaged by sludge removal or other mechanical equipment used
in the impoundment.  Where such equipment is used,  EPA recommends
a minimum of 45 centimeters (18 inches) of protective soil, or
the equivalent covering the top liner.  EPA believes this will
be sufficiently protective in most cases since sludge removal
equipment is usually carefully controlled.  Additionally, some
liner materials are known to be degraded substantially by sun-
light.  In some circumstances, wind can get under the edge of
exposed liners, causing flapping and whipping, which can lead to
tears.  These problems have occurred most commonly above the
liquid level near the edge of the liner.  As a result, it has
become common practice to cover exposed liner areas with six
inches or so of earth materials to hold the liner down and
prevent degradation.  Of course, if the design is such that
wind creates no difficulties, and if it is known that the liner
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is not subject to solar degradation, then these precautions are



not necessary.



     Chemical testing is prudent because synthetic liners are



degraded by certain species which may be present in the waste.



Because wastes and liner chemical characteristics are almost



infinitely variable, it is difficult to generalize concerning



incompatibility.  The Agency therefore prefers test data as the



preferable way to demonstrate the compatibility of waste and



liner materials, but recognizes that historic data (results



elsewhere with similar wastes) or theoretical chemistry may



provide sufficient information in some cases.  Data currently



available to EPA indicate the following combinations of waste



types and liner materials are often incompatible:



     (a)  Chlorinated solvents tend to dissolve polyvinyl



          chloride (PVC)



     (b)  Chlorosulfonated polyethylene can be dissolved by



          aromatic hydrocarbons.



     (c)  Clays may exhibit high permeability when exposed to



          concentrated organics,  especially organics of high



          and low pH



     (d)  Asphaltic materials may dissolve in oily wastes



     (e)  Concrete and lime based materials are dissolved by



          acids



The Agency is currently developing a more comprehensive summary



of waste/liner compatibility information which will be included



in a later edition of this document.
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     An acceptable test method for evaluating waste/liner com-



patibility is included in the Appendix to this document.  The



test method exposes a liner sample to the waste or leachate



encountered at the unit.  After exposure, the liner sample



is tested for important characteristics—saturated hydraulic



conductivity in the case of soil liners; strength (tensile,



tear, and puncture) in the case of synthetics.  The Agency



considers any significant deterioration in any of the measured



properties to be evidence of incompatibility unless a convincing



demonstration can be made that the deterioration exhibited



will not impair the integrity of the liner over the life of



the unit.  Even though the tests may show the amount of deteri-



oration to be relatively small, the Agency is concerned about



the accumulative effects of exposure over very much longer



periods than those actually tested.



     The Agency had intended to incorporate the National Sanita-



tion Foundation's (NSF) standard specifications for flexible



membrane liners as part of this guidance.  This would have



provided  minimum recommendations with regard to physical



properties, construction practices, seaming tests, etc.  An



NSF committee has been studying the subject for some time, and



EPA believes that the specifications which are being developed



are reasonable and well thought out.  However, at this point,



the NSF has not formally adopted the draft standards.  Therefore,



given the possibility that they might still be changed, EPA



believes it prudent to wait for formal adoption by the NSF before



incorporating them into this guidance document.  The NSF



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specifications are not intended to comprehensively cover the
myriad of hazardous waste applications, however.  Therefore,
the Agency believes that some augmentation of the NSF specifica-
tions is appropriate.  A few additions have been made (e.g.,
the 30 mil thickness requirement) and more may be incorporated
if experience warrants.
     Once the NSF strength secifications have been published,
EPA plans to incorporate them in conjunction with the compatibility
test method for synthetic liners attached, in an improved method
of evaluating liner compatibility.  While the Agency does not
want to prejudge how this may be done, one possible approach
might be to extrapolate the strength curves developed by the
test method to the expected life of the unit.  The expected
strength at that'time could then be compared against minimally
acceptable strength levels, e.g., the NSF strength specifications
or some acceptable fraction of them.  The Agency is interested
in comments, suggestions, and data on the subject of evaluating
strength loss on exposure to chemical leachates.
     Soil liners will normally be of clay soils.  They should
have a saturated hydraulic conductivity of not more than 1 X 10~7
cm/sec and be at least 60 centimeters (2 feet) thick.  To
minimize the transmission of waste or leachate fluids, the
soil liner should be as tight as practical.  Many clays can
readily be recompacted to meet the specified level.  It is not
clear,  however, that recompactiny to meet a tighter specifi-
cation can be routinely accomplished.  In concert with the
philosophy of these designs,  soil liners are usually incorporated
                               21

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as backup systems and are depended upon to minimize the rate
of liquid flow through them (except in the case of storage
impoundments to be discussed later).  Thickness of the soil is
not as important as other factors in minimizing flow but a
minimum thickness is necessary to retain structural stability
(reduce cracking potential, etc.).  Two feet is generally
accepted to be a minimum stable thickness for recompacted
clay.
     When discussing the relative tightness of soils, the term
permeability is most often used.  This is a generic term, refer-
ing to the property in general.  In this guidance, EPA uses the
more specific term—"hydraulic conductivity".  An acceptable
method for soil hydraulic conductivity has been included in the
Appendix to this document.
     I_n situ soils can be considered acceptable as soil liner
material provided the specifications in this guidance are met.
Natural soil liners should be free of conduits and channels
which would convey liquids through the liner.  This includes
root holes, sand lenses, cracks, fractures, etc.
     In addition to meeting the other specifications specified for
clay liners, those wishing to use a single clay liner for storage
impoundments should be convinced that the liner system is capable of
retarding liquid flow through it to the extent that the liquid is
wholly contained within the liner through the life of the
unit.  Ideally, one would calculate containment time on an
unsaturated basis, but the unsaturated flow equations are
difficult, complex, and controversial.  As a surrogate which
                               22

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approximates the ideal and can be practically applied, the Agency



has chosen a transit time formula assuming saturated conditions.




The formula is based on the life of the facility through closure,



the porosity of the soil liner, the saturated hydraulic conducti-



vity, and the maximum fluid head in the surface impoundment.



   The determination of the effective porosity of the soil is



difficult to do in practice.  Because of the controversial nature



of the determination of effective porosity, the Agency believes



total porosity should be used in the calculation even though



in doing so the requirement is somewhat less protective.  The



Agency is evaluating  methods for determining effective porosity



and may change this guidance should confidence in a specific



method be established.



     Use of the saturated flow equation is environmentally conser-



vative, and will result in a thicker soil liner than would abso-



lutely be necessary to assure containment in the liner system.



This is partially offset however by the use of total porosity



instead of effective porosity which causes the equation to be



somewhat less protective.  Additionally, the saturated flow equa-



tion does not account for the effects of capillary tension which



will also cause the regulation to be somewhat less protective.



On balance, the use of total porosity and the lack of consi-



deration of capillary tension will somewhat offset the error



introduced by use of a saturated flow equation.  While EPA



realizes that this formula is not perfect, it is the only



performance based approach which is practically implementable.



It is somewhat environmentally conservative; erring on the




                               23

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side of added protection.  This is prudent, in the Agency's



opinion, given the uncertainties associated with prediction



of pollutant movement through soils.



     Owners and operators choosing to incorporate a leak detec-



tion system between a double liner design as a means of qualify-



ing for exemption from the ground-water protection and associ-



ated monitoring requirements of Subpart F in accordance with



§264.222, must incorporate a secondary liner,  under the leak



detection system, which meets the containment requirement for



liner systems under §264.221(a).  For most surface impoundments,



this means that a synthetic secondary liner must be used as a



minimum.  If the impoundment is being designed to operate for



more than 30 years, then the synthetic liner should be backed



up by a tertiary soil liner meeting the specifications discussed



herein.  The regulations are written to require prevention of



release by the secondary liner in surface impoundments exempted



from Subpart F because the owner or operator may choose, upon



detection of a leak, to convert his unit to the same status



as other surface impoundments installing ground-water monitoring



facilities and becoming subject to the ground-water protection



standards of Subpart F.  Most other surface impoundments must



have a liner system capable of preventing migration of liquids.



E.   Cap (Final Cover) Design



     1.   The Regulation



     The cap or final cover must be designed to minimize infil-



tration of precipitation into the surface impoundment after



closure.  It must be no more permeable than the liner system.



                               24

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It must operate with minimum maintenance and promote drainage



from its surface while minimizing erosion.  It must also be



designed so that settling and subsidence are accommodated to



minimize the potential for disruption of continuity and function



of the final cover.



     2.   Guidance



     (a)  The cap or final cover should be placed over the



surface impoundment after the waste has been solidified and



compacted enough to support it.  Solidification and fixation



processes often take days or weeks to completely stabilize.



Final cover should not be applied before stabilization is nearly



complete.



     (b)  The cap (final cover) should consist of the following



as a minimum:



     (1)  A vegetated top cover, as described in paragraph (c)



of this section;



     (2)  A middle drainage layer as described in paragraph (d)



of this section; and



     (3)  A low permeability bottom layer as described in



paragraph (e) of this section.



     (c)  The vegetated top cover should:



     (1)  Be at least 60 centimeters (24 inches) thick;



     (2)  Support vegetation that will effectively minimize



erosion without need for continuing application of fertilizers,



irrigation, or other man-applied materials to ensure viability



and persistence (Fertilizers, water, and other materials may



be applied during the closure or post-closure period if necessary



to establish vegetation or to repair damage.);



                               25

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     (3)  Be planted with persistent species that will effect-

ively minimize erosion, and that do not have a root system

that will penetrate beyond the vegetative and drainage layer;

     (4)  Have a final top slope, after allowance for settling

and subsidence, of between three and five percent, unless the

owner or operator knows that an alternate slope will effectively

promote drainage and not subject the closed facility to erosion.

For slopes exceeding five percent,  the maximum erosion rate

should not exceed 2.0 tons/acre using the USDA Universal Soil Loss

Equation (USLE); and

     (5)  Have a surface drainage system capable of conducting

run-off across the cap without forming erosion rills and gullies.

     (d)  The drainage layer should:

     (1)  Be at least 30 centimeters (12 inches) thick with a

saturated hydraulic conductivity not less than 1 X 10~3 cm/sec;

     (2)  Have a final bottom slope of at least two percent,

after allowance for settling and subsidence;

     (3)  To prevent clogging, be overlain by a graded granular

or synthetic fabric filter.  Where a granular filter is used,

the grain size ratio should meet the following criteria:

                     D15 (filter soil)       < 5
                     D85 (drainage layer)    =

                     D50 (filter soil)       < 25
                     D50 (drainage layer)    =

          and        D15 (filter soil)       = 5-20
                     D15 (drainage layer)

          where:

               D15 = grain size, in millimeters, at which 15% of

                     the filter soil used, by weight, is finer;

                               26

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               D85 = grain size, in millimeters, at which



                     85% of the drainage layer media, by



                     weight, is finer;



               D50 = grain size, in millimeters, at which



                     50% of the filter soil or drainage media,



                     by weight, is finer; and



     (4)  Be designed so that discharge flows freely in the



lateral direction to minimize head on and flow through the low



permeability layer.



     (e)  The low permeability layer should have two components:



     (1)  The upper component should:



     (A)  Consist of at least a 20 mil synthetic membrane;



     (B)  Be protected from damage below and above the membrane



by at least 15 centimeters (6 inches) of bedding material no



coarser than Unified Soil Classification System (USCS) sand (SP)



and which is free of rock, fractured stone, debris, cobbles,



rubbish, roots, and sudden changes in grade (slope).  The



drainage layer and lower soil (clay) component may serve as



bedding materials when in direct contact with synthetic caps



if they meet the specifications contained herein;



     (C)  Have a final upper slope (in contact with the bedding.



material) of at least two percent after allowance for settling;



and



     (D)  Be located wholly below the average depth of frost pene-



tration in the area;



     (2)  The lower component should:
                               27

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     (A)  Include at least  60 centimeters (24 inches) of soil



recompacted to the maximum practical extent, but capable, if



placed on a firm base, of being recompacted to a saturated



hydraulic conductivity of not more than 1 X 10""7 cm/sec;



     (B)  Have the soil emplaced in lifts not exceeding 15



centimeters (6 inches) before compaction to maximize the



effectiveness of compaction;



     (f)  In designing the final cover, owners and operators



should estimate and accommodate the amount of settling and



subsidence expected as a result of degradation and long-term



consolidation of waste.



     3.   Discussion



     The guidance calls for placing the final cover once the



waste remaining in the surface impoundment has been solidified



through sorption, fixation, or some other means and after it has



stabilized and been compacted sufficiently to support the final



cover.  Some of the fixation processes take days or weeks to



stabilize and placement of final cover should not commence until



the process is nearly complete.



     The Ajency believes that a three layer final cover  (cap)



will adequately minimize infiltration of precipitation, which



is the primary purpose of the final cover.  The final cover



acts to minimize infiltration by causing precipitation to run



off through use of slopes, drainage layers, and impermeable



and slightly permeable barriers.  By minimizing infiltration,



the generation of leachate will also be minimized, thereby



reducing long-term discharge of pollutants to the ground water



                               28

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to a bare minimum.  To prevent the "bathtub effect," i.e., to



prevent the landfill from filling with leachate after closure,



the final cover must be no more permeable than the most impermeable



component of the liner system (or of the underlying soils).  In



this way, no more precipitation is allowed to infiltrate into



the closed impoundment than can escape through the bottom liner.



Prevention of the "bathtub effect" is important to eliminate the



possibility of surface overflow or migration through porous



surface strata.  Other functions of the final cover include



prevention of contamination of surface run-off, prevention of



wind dispersal of hazardous wastes, and prevention of direct



contact with hazardous wastes by people and animals straying



onto the site.



     The top layer should have at least two feet of soil capable



of sustaining plant species which will effectively minimize



erosion.  Two feet was chosen because it will accommodate the



root systems of most nonwoody cover plantings and is typical



practice within the waste management industry today.  Species



planted should not require continuing  man-made applications of



water or fertilizers to sustain growth since such applications



cannot be guaranteed in the long term.  Application of water and



fertilizer is, of course, acceptable during the early stages of



the post-closure care period as the plant growth is being



established.  The plant species chosen should also not have



root systems which can be expected to penetrate beyond the



vegetated and drainage layers.  If they penetrate deeper, they



can damage the integrity of the low permeability layer.



                               29

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     After allowance for settling and subsidence, the final slope



should be at least three percent to prevent pooling due to



irregularities of the surface and vegetation but less than



five percent to prevent excessive erosion.  Owners and operators



using different final slopes should determine that an alternate



slope will not be beset with erosion problems and that it will



promote efficient drainage.



     The U.S. Department of Agriculture Universal Soil Loss



Equation (LISLE) is recommended as a tool for use in evaluating



erosion potential.  The USLE predicts average annual soil loss



as the product of six quantifiable factors.  The equation is:



               A = RKLSCP



     where     R = rainfall and run-off erosivity index



          K = soil erodibility factor, tons/acre



          L = slope-length factor



          S - slope-steepness factor



          C = cover/management factor



          P = practice factor



The data necessary as input to this equation are described in



Evaluating Cover Systems for Solid and Hazardous Waste  (SW-867),



September 1980, U.S. EPA.  The maximum rate of erosion for any



part of the cover should not exceed 2.0 tons/acre in order to



minimize the potential for gully development and future main-



tenance.  The agricultural data base indicates that rates as low



as 1/3 ton per acre are achievable for a silt-loam soil, sloped



four percent with a blue grass vegetative cover.  The Agency



believes that two tons per acre is more readily achieved and



                               30

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does not significantly increase cover maintenance.  The top
layer should also have some means of conducting runoff  (e.g.,
swales or conduits) to safely pass run-off  velocities and
volumes without eroding the cover.
     The second layer or drainage layer is  analogous in function
to the leachate collection system over the  liner of a landfill.
It should be at least 12 inches thick to provide capacity to
handle water from major sustained storm events, and should be
constructed of porous materials (at least 1 X 10~3 cm/sec
hydraulic conductivity).  Drainage tiles or other collection
devices are not necessary.  The Agency believes that the combin-
ation of very porous media, a final minimum two percent slope
after settling, and the impermeable nature  of the layer beneath
will effectively conduct precipitation infiltrating the vegeta-
tive layer, off of the unit.  As with the leak collection
system, the drainage layer should be overlain with a graduated
granular or synthetic fabric filter to prevent plugging of the
porous media with fine earth particles carried down from the
vegetated layer.  To prevent fluid from backing up into the
drainage layer, the discharge at the side should flow freely.
     The function of the low permeability layer is to reject
fluid transmission, thereby causing infiltrating precipitation
to exit through the drainage layer.  It should consist of at
least two components.  The upper component  should be at least
a 20 mil thick synthetic membrane.  While the regulations do
not specify that the cap prevent infiltration, the requirement
that it be no more permeable than the bottom liner, as a practical
                               31

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matter, necessitates the use of a synthetic membrane.  This is
so because the regulatory requirement for the liner system
does specify that liquids be contained, and this will be trans-
lated, in most cases, into a very nearly impermeable synthetic
membrane liner.
     The minimum thickness specified for the synthetic component
of the final cover (20 mil) is less than that recommended for
the liner (30 mil) because (1) the final cover is not expected
to come in contact with chemical wastes which will tend to
hasten failure, and (2) once placed, the potential for damage
is small as compared to the potential for underliner damage
where waste is in contact with the liner throughout the operating
life of the cell.  While intact (30 + years in the absence of
damage), the synthetic component will essentially prevent
transfer of precipitation through it and leachate production
should be very nearly zero.  As with underliners, synthetic
caps should be protected from from punture and tears by at
least six inches of bedding materials with the consistency of
sand or finer.  In most cases, the drainage layer media above
the synthetic cap, together with the soil (clay) liner under
it, can effectively function as the bedding material.
     Even with protection from damage, the synthetic cap will
not last forever.  At some point, perhaps in the far distant
future, the synthetic membrane will degrade.  At that time,
the function of minimizing infiltration will fall to the second
component, a 2-foot minimum clay soil cap with a maximum hydraulic
conductivity of 1 X 10~7 cm/sec.  Although some small amount
                               32

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of precipitation will seep through this secondary cap, the
amount of leachate generated will be quite small and escape to
the ground water should be mimimal.  Unless damaged or affected
by differential settling, the secondary soil liner should
remain intact and effective for all time.  One source of damage
is frost heaving which can disrupt the continuity of the
impermeable layers.  For this reason, the impermeable layer
should be wholly below the average depth of frost penetration
in the area.  This may necessitate a thicker cover than would
otherwise be necessary.
     One of the more difficult problems associated with de-
signing final cover is how to allow for settling and subsidence.
Settling occurs as a result of natural compaction and consoli-
dation and biological degradation of organics.  It tends to be
relatively uniformly distributed and usually occurs shortly
after closure.  Subsidence is a more difficult problem since
it tends to be unevenly distributed, resulting in differential
sinking which in turn can cause disruption in continuity of
the final cover.  It most often occurs as the result of final
release of liquids from, and collapse of drums and is, therefore,
not normally a major problem with closed surface impoundments.
Settling on the other hand, may pose a significant problem if
remaining wastes are high in organic content or if organic
sorbants (e.g., sawdust or paper) are used to solidify the
wastes.  Chemical fixation processes are usually inorganic in
nature and are not prone to significant settling once stabili-
zation is complete.
                               33

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     EPA intends to develop specific design requirements which
will ensure adequate allowance for settling and subsidence.  As
of this writing, however, the Agency lacks sufficient information
to judge the effectiveness of various design options.  Therefore,
this guidance suggests simply that owners and operators estimate
the amount of subsidence and allow for it in the final cover
design as best they can.  The final result should be a minimum
three percent final slope after settling and subsidence.  During
the postclosure period, the regulations require that the
damaging effects of settling and subsidence (e.g., disruption
of the continuity and slope of the cap) be repaired.  It thus
behooves the owner or operator to adequately allow for subsidence
and settling.  As the Agency evaluates alternative methods of
designing final cover to effectively allow for settling  and
subsidence, it will issue further guidance or perhaps even
additional regulations covering the subject.
     One suggestion which owners and operators may consider as
a means of at least partially accomodating settling and sub-
sidence, is to stage final closure and the placement of the
final cover.  Unsubstantiated information from the field leads
EPA to believe that the most severe subsidence and settling
problems occur rather soon after closure.  It may be preferable
therefore, from both an environmental and cost standpoint, to
delay placement of the relatively expensive final cover for six
months or more  in those cases where substantial subsidence or
settling are expected.  By so doing, expensive repairs to the
final cover may be avoided.  This would require an extension in
                               34

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the 180 day limit to the closure period  imposed in Subpart G.
In deciding whether to grant such an extension, in accordance
with the rules of Subpart G, the permitting official will
normally require installation of an expendable interim cover,
capable of minimizing precipitation migration  into the unit.
The Ayency solicits information on the effectiveness of this
and other approaches to dealing with the settling/subsidence
problem.
F.   Freeboard Control
     1.   The Regulations
     The regulations require simply that the owner or operator
prevent overtopping of his surface impoundment from virtually
any eventuality, including normal or abnormal  operations, over-
filling, wind and wave action, rainfall, equipment malfunctions,
and human error.
     To implement this requirement, the owner  or operator must
demonstrate in his permit application that design features and
operating procedures at his operation will prevent overtopping.
If acceptable to the permitting official, these features and
procedures will be incorporated in the permit.
     2.   Guidance
     (a)  Where possible, surface impoundments should be designed
with outfall mechanisms such as weirs or spillways which are
relatively insensitive to inflow.
     (b)  Where outfalls are sensitive to inflow,  i.e., where
adjustments must be made to maintain impoundment freeboard as
inflow increases, outfall devices (or inflow controls) should be
automaticaly controlled by signals from level-sensing instruments.
                               35

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     (c)  Except when equipped with inflow insensitive outfalls



as described in (a) above, surface impoundments should be



equipped with a high-level alarm based on a different level



sensor than that used for automatic control.



     (d)  Surface impoundments should be designed to maintain



at least 60 centimeters (two feet) of freeboard unless it is



known that normal fluctuations in level and maximum wave action



will not cause overtopping.



     (e)  A surface impoundment should be designed so that any



flow of waste into the impoundment can be immediately shut off



in the event of overtopping or liner failure.



     (f)  A surface impoundment should have a run-on control



system designed to prevent flow into the impoundment during the



peak discharge from a 100-year storm unless the impoundment is



designed to accommodate the extra flow without detrimental



effects to the impoundment or appreciable loss of freeboard.



     3.   Discussion



     Preventing overtopping of surface impoundments is not



normally a difficult engineering  problem.  Many impoundments are



operated on a flow through basis.  Typically, these are impound-



ments used for treatment of wastes; biological oxidation lagoons



are a common example, though not one normally associated with



hazardous wastes.  Frequently, these impoundments are designed



with simple spillway or weir-type discharge structures which



maintain a constant freeboard level in the impoundment.  With



this type of arrangement, the sensitivity of freeboard level is



dependent directly on the relative width of the spillway or weir,



                               36

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Normally, but not always, these structures are sufficiently wide
so that freeboard level is insensitive to normal changes in flow.
In these cases, all that is necessary is the provision of a
modest freeboard level sufficient to deal with wave action and
with the minor fluctuations which will occur as flow changes.
The Agency believes two feet will be sufficient in virtually
all cases where discharge structures of this type are used.
     Some impoundments are designed with other discharge
arrangements.  Some, such as circular weirs, operate on the same
principle as those discussed above, but because the effective
discharge width of the device is often narrow relative to
potential flow fluctuations, they may be overwhelmed by abnormal
rainfall events or malfunctions in the production equipment which
feeds wastes to the impoundment.  Other arrangements require
adjustment to the discharge structures to maintain freeboard
level.  A common design of this type incorporates underflow
pipes through a dike.  Freeboard level in these designs is
usually controlled by a valve on the pipe.   Others operate off
of a sump arrangement with the freeboard level controlled by
turning a pump on and off.  Storage impoundments are often
constructed this way.  Some other impoundments, usually those
operated as seepage or evaporation impoundments, have no dis-
charge arrangment.  Obviously, with no discharge, the freeboard
level is very sensitive to substantial changes in inflow to
the impoundment.
     Where freeboard level is sensitive to flow changes, there
are a number of design and operating alternatives which can be
                               37

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adopted to provide adequate protection against overtopping:
     (1)  Emergency spillways or overflow piping arrangements
can sometimes be provided which can be connected to holding
ponds or tanks to contain the overflow.  If these latter units
are to be used only in the unlikely event of an emergency,
they need not be permitted.  However, if they are to be used on
a statistically predictable recurring basis for surge capacity,
permitting is necessary.  This will require exercise of some
judgment on the part of the permitting official.
     (2)  Another alternative is to control the discharge
device automatically based on freeboard level.  The underflow
valve can be opened or closed automatically to maintain a set
freeboard level through signals from level-sensing instruments.
Reliable level sensing devices have been available for many
years and are usable in most situations.  Discharge pumps can be
similarly controlled (turned on and off to maintain level with-
in a range).  Where it can be accommodated from the point of
view of production or operation of the rest of the facility,
it may be possible to automatically control the amount of waste
flowing into the impoundment through valves or pumps based on
freeboard level.
     (3)  Outfall devices can also be controlled manually.  In
these cases, the owner or operator must be prepared to demon-
strate that he either maintains sufficient freeboard to accom-
modate any reasonably possible increase in influent flow or that
the combination of the rate of possible flow increases coupled
with the frequency of operator inspections to control discharge
                               38

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will eliminate potential overtopping due to sudden unnoticed



increases in level.  In these cases, the frequency of control



inspections must be specified in the inspection schedule and



thus in the permit.



     (4)  Some impoundments have no discharge devices.  In these



cases, owners or operators must be able to demonstrate either



that the rate of seepage or evaporation is such that overflow



is not possible even under maximum possible inflow rates or,



more probably, that operating procedures are in effect which



will effectively control inflow so that overtopping conditions



will not occur.  A convincing demonstration should be required



in any case.



     Of the acceptable options discussed above, the Agency



clearly favors automatic controls and/ or provision of foolproof



arrangements such as weir discharges or emergency collection



devices (tanks or ponds).  These are not as sensitive to human



error as are those arrangements requiring human inspection and



manual operation.  Automatic control devices based on level



sensors are, however, subject to malfunctions.  Because of



this, the .Agency recommends that any freeboard control arrange-



ment that is sensitive to inflow variations (i.e., all except



those using weirs, spillways, or similar devices,  or where



possible inflow variations cannot cause overflow)  be equipped



with an alarm to warn of loss of freeboard so emergency action



can be taken to prevent overtopping.  Typically, these will also



be based on a level sensor device, and the Agency recommends



that a different sensing unit and different type of device be



                               39

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used than that used for automatic control.  This will help



ensure that both do not fail at the same time.



     EPA believes that two feet of freeboard will normally pro-



vide sufficient protection against overtopping due to inflow



fluctuations or wave action.  However, where manual operation



is involved, freeboard levels substantially greater may be



necessary to assure adequate protection.  Smaller freeboard



levels may be justified if the owner or operator can demonstrate



that level variations due to possible flow changes are very



small or that the automatic level control response is such



that level variations will be very small.



     In the event overtopping does occur, in spite of the safe-



guards built into the system, or in the event of some other



catastrophic failure (e.g., dike failure), there must be some



way to quickly shut off inflow to the impoundment.  The Agency



does not care how this is accomplished so long as it can be



done quickly and without causing significant environmental or



human health problems elsewhere.  Possible options might include



provision of redundant units or immediate shutdown of production



operations feeding the impoundment.



     Many ponds and lagoons are designed, either purposefully



or circumstantially, to collect run-off from adjacent plant



areas or even sometimes from whole watersheds.  Depending on



the magnitude of rainfall events and the size of the drainage



area relative to the impoundment capacity, storm run-off can



provide an overwhelming inflow to the impoundment, causing



overtopping.  Unless it can be shown at the time of permitting




                               40

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that the impoundment is designed to handle storm water without



appreciable loss of freeboard or other detrimental effects on



the impoundment, a run-on control system should be installed.



The Agency recommends that the capacity of the run-on control



system be designed to divert the maximum flow from a 100-year



storm event.  This is the most severe storm event for which



historical meteorologic data is normally available.  Choice of



this rather stringent storm event indicates the Agency's level



of concern over potential overtopping of surface impoundments



containing hazardous wastes.  This level of concern steins not



only from the inherent threat posed by the uncontrolled escape



of hazardous wastes into the environment but also from the



potential for overtopping to threaten the very stability of the



dike itself; leading to a possible complete washout with



accompanying catastrophic results.  Nevertheless, there are



some events, including storm events with greater than a 100



year severity,  that separately or in combination can result in



overtopping, which must be ignored as a practical matter.  Many



of these border on the absurd such as the remote possibility of



an airplance crash in the impoundment.  Others are improbable



combinations of events such as the possibility that all liquid



containing storage tanks in a manufacturing operation will



break at once, releasing their contents to the sewer system



feeding the impoundment, causing it to overflow.  EPA does



intend such events to be protected against.  Judgement must be



exercised during the permit process in dealing with the more



remote possibilities.



                               41

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           APPENDIX A
METHODS FOR DETERMINING SATURATED
HYDRAULIC CONDUCTIVITY, SATURATED
   LEACHATE CONDUCTIVITY, AND
     INTRINSIC PERMEABILITY

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                       TABLE OF CONTENTS

                                                           Page

1.0  INTRODUCTION   	    1-1

     1.1  SCOPE AND APPLICATION	    1-1

     1.2  DEFINITIONS	    1-5

          1.2.1  Units	    1-5
          1.2.2  Fluid potential or head  .	    1-6
          1.2.3  Hydraulic potential or head	    1-6
          1.2.4  Hydraulic conductivity 	    1-6
          1.2.5  Fluid conductivity 	    1-7
          1.2.6  Leachate conductivity  	    1-8
          1.2.7  Aquifer	    1-8
          1.2.8  Confining layer	    1-8
          1.2.9  Transraissivity	    1-8

     1.3  TEMPERATURE AND VISCOSITY CORRECTIONS  	    1-9

     1.4  INTRINSIC PERMEABILITY  	  1-10

     1.5  RANGE OF VALIDITY OF DARCY'S LAW	1-10

     1.6  METHOD CLASSIFICATION   	  1-12

2.0  LABORATORY METHODS 	    2-1

     2.1  SAMPLE COLLECTION FOR LABORATORY METHODS   .  .  .    2-1

     2.2  CONSTANT-HEAD METHODS 	    2-1

     2.3  FALLING-HEAD METHODS  	    2-3

     2.4  GENERAL TEST CONSIDERATIONS 	    2-5

          2.4.1  Fluid Supplies to be Used	    2-5
          2.4.2  Pressure and Fluid Potential  Measurement    2-6

     2.5  CONSTANT-HEAD TEST WITH CONVENTIONAL
          PERMEAMETER   	    2-6

          2.5.1  Applicability	    2-6
          2.5.2  Apparatus	    2-7
          2.5.3  Sample Preparation 	    2-7
          2.5.4  Test Procedure	    2-9
          2.5.5  Calculations	    2-10

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            TABLE OF CONTENTS (Continued)
2.6  FALLING-HEAD TEST WITH CONVENTIONAL
     PERMEAMETER   	2-10

     2.6.1  Applicability	2-10
     2.6.2  Apparatus	  2-10
     2.6.3  Sample Preparation 	  2-11
     2.6.4  Test Procedure	2-11
     2.6.5  Calculations	2-11

2.7  MODIFIED COMPACTION PERMEAMETER METHOD  ....  2-12

     2.7.1  Applicability	2-12
     2.7.2  Apparatus	2-12
     2.7.3  Sample Preparation	2-12
     2.7.4  Test Procedure	2-13
     2.7.5  Calculations	2-13

2.8  TRIAXIAL-CELL METHOD WITH BACK PRESSURE ....  2-13

     2.8.1  Applicability	2-13
     2.8.2  Apparatus  . '.	2-15
     2.8.3  Sample Preparation 	  2-15
     2.8.4  Test Procedure	2-15
     2.8.5  Calculations	2-19

2.9  PRESSURE-CHAMBER PERMEAMETER METHOD 	  2-19

     2.9.1  Applicability	2-19
     2.9.2  Apparatus	2-19
     2.9.3  Sample Preparation	  2-19
     2.9.4  Test Procedure	2-21
     2.9.5  Calculations	2-21

2.10 SOURCES OF ERROR FOR LABORATORY TEST FOR
     HYDRAULIC CONDUCTIVITY  	  2-21

2.11 LEACHATE CONDUCTIVITY USING LABORATORY METHODS   2-23

     2.11.1 Applicability  	  2-23
     2.11.2 Leachate Used	2-24
     2.11.3 Safety 	  2-24
     2.11.4 Procedures 	  2-25
     2.11.5 Apparatus  	  2-25
     2.11.6 Measurements 	  2-25
     2.11.7 Calculations 	  2-26
                         ii

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                 TABLE OF CONTENTS (Continued)

                                                           Page
3.0  FIELD METHODS	   3-1

     3.1  WELL-CONSTRUCTION CONSIDERATIONS  	   3-2

          3.1.1  Well Installation Methods	   3-2
          3.1.2  Wells Requiring Well Screens 	   3-3
          3.1.3  Wells Not Requiring Well Screens ....   3-5

     3.2  WELL DEVELOPMENT	   3-5

     3.3  DATA INTERPRETATION AND TEST SELECTION
          CONSIDERATIONS  	   3-6

     3.4  SINGLE WELL TESTS	   3-8

          3.4.1  Method for Moderately Permeable
                 Formations Under Confined Conditions  .  .   3-8
          3.4.2  Methods for Extremely Tight Formations
                 Under Confined Conditions	3-13
          3.4.3  Methods for Moderately Permeable
                 Materials Under Unconfined
                 Conditions	3-17

     3.5  MULTIPLE WELL TESTS   	3-22

     3.6  ESTIMATES OF HYDRAULIC CONDUCTIVITY FOR
          COARSE-GRAINED MATERIALS  	  3-22

     3.7  CONSOLIDATION TESTS 	  3-25

     3.8  FRACTURED MEDIA   	3-26

4.0  CONCLUSION	   4-1

5.0  REFERENCES	   5-1

6.0  APPENDIX A	   6-1
                              iii

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                 TABLE OF CONTENTS  (Continued)


                        LIST OF TABLES
Table No.                                                  Page

   A        HYDRAULIC AND LINER CONDUCTIVITY
            DETERMINATION REQUIREMENTS FOR SURFACE
            IMPOUNDMENTS, WASTE PILES, AND LANDFILL
            COMPONENTS, AS CITED IN RCRA GRUIDANCE
            DOCUMENTS AND DESCRIBED IN SW-846     ....     1-2

   B        SUMMARY OF PUBLISHED DATA ON POTENTIAL
            ERRORS IN USING DATA FROM LABORATORY
            PERMEABILITY TESTS ON SATURATED SOILS   .  .  .   2-22

   C        HYDRAULIC CONDUCTIVITIES ESTIMATED FROM
            GRAIN-SIZE DESCRIPTIONS  	   3-24
                        LIST OF FIGURES
Figure No.

    1       PRINCIPLE OF THE CONSTANT HEAD METHOD   .  .  .    2-3

    2       PRINCIPLE OF THE FALLING HEAD METHOD    .  .  .    2-4

    3       APPARATUS SETUP FOR THE CONSTANT HEAD
            AND FALLING HEAD METHODS	    2-8

    4       MODIFIED COMPACTION PERMEAMETER  	   2-14

    5       SCHEMATIC DIAGRAM OF TYPICAL TRIAXIAL
            COMPRESSION APPARATUS FOR
            HYDRAULIC CONDUCTIVITY TESTS WITH
            BACK PRESSURE	2-15

    6       PRESSURE CHAMBER FOR HYDRAULIC
            CONDUCTIVITY 	   2-20

    7       GEOMETRY AND VARIABLE DEFINITION FOR
            SLUG TESTS IN CONFINED AQUIFERS  	   3-10

    8       SCHEMATIC DIAGRAM FOR PRESSURIZED
            SLUG TEST METHOD   	3-15

    9       VARIABLE DEFINITIONS FOR SLUG TESTS
            IN UNCONFINED MATERIALS  	   3-18

   10       CURVES DEFINING COEFFICIENTS A, B, AND  C
            to L/rw	3-21
                              iv

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                           METHOD SW-846

               SATURATED HYDRAULIC CONDUCTIVITY,
             SATURATED LEACHATE  CONDUCTIVITY,  AND
                    INTRINSIC PERMEABILITY
                       1.0  INTRODUCTION


1.1  SCOPE AND APPLICATION

This section presents methods available to  hydrogeologists  and

geotechnical engineers for determining the  saturated  hydraulic

conductivity of earth materials  and  conductivity  of soil  liners

to leachate, as outlined by the  Part 264  permitting rules for

hazardous-waste disposal facilities.  In  addition, a  general

technique to determine intrinsic permeability  is  provided.  A

cross reference between the applicable parts of the RCRA

Guidance Documents and associated Part 264  Standards  and  these

test methods is provided by Table A.


Part 264 Subpart F establishes standards  for ground-water

quality monitoring and environmental performance.  To

demonstrate compliance with these standards, a permit applicant

must have knowledge of certain aspects of the  hydrogeology

at the disposal facility, such as hydraulic conductivity, in

order to determine the compliance point and monitoring well

locations and in order to develop remedial  action plans when

necessary.


In this report, the laboratory and field methods  that are con-

sidered the most appropriate to  meeting the requirements of

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                                                                1-2
                             TABLE A

         HYDRAULIC AND LINER CONDUCTIVITY DETERMINATION
                 METHODS FOR SURFACE IMPOUNDMENT
          WASTE PILE, AND LANDFILL COMPONENTS, AS CITED
       IN RCRA GUIDANCE DOCUMENTS    AND DESCRIBED IN SW-846
Surface Impoundments
Guidance
Associated Regulation
Corresponding
   SW-846
   Section
Soil liner hydraulic
conductivity
Guidance section D{2)(b)(1)
and D(2)(c)(1)/Section
264.221(a),(b)
      2.0
Soil liner leachate
conductivity
Guidance section D(2) (b)(2)
and D(2)(c)(2)
      -2.11
Leak detection system
Guidance section C(2)(a)/
Section 264.222
                                                               2.0
Final cover drain
layer


Final cover low
permeability layer
Guidance section E(2)(d)(I)/
Section 264.228
Guidance section E(2)(e)(2)(A)/
Section 264.228
      2.0


      2.0
General Hydrogeologic
site investigation
264 subpart F
      3.0
  RCRA Guidance Document:  Surface Impoundments, Liner Systems,
  Final Cover, and Freeboard Control.  Issued July, 1982.

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                                                              1-3
     Waste Piles
             .„
   Guidance Cite—'
   Associated Regulation
Corresponding
   SW-846
   Section
Soil liner hydraulic
conductivity
Guidance section D(2)(b)(i)
and D(2)(c) (i)/
Section 264.251(a)(1)
      2.0
Soil liner leachate
conductivity
Guidance section D(2)(b)(ii)
and D(2)(c)(ii)
      2.11
Leak Detection
System
Guidance section C{2)(a)/
Section 264.252 (a)
      2.0
Leachate collection
and renewal system
Guidance section C(2)(a)/
Section 264.251 (a) (2)
      2.0
General hydrogeologic
site investigation
264 subpart F
      3.0
-'RCRA Guidance Document:  Waste Pile Design, Liner Systems.
  Issued July»- 1982.

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                                                                 1-4
     Landfills
 Guidance Cite—
 Associated Regulation
Corresponding
   SW-846
   Section
Soil liner hydraulic
conductivity
 Guidance section D(2)(b)(I)/
 Section 264.301(a)(1)
      2.0
Soil liner leachate
conductivity
 Guidance section D(2) (b)(2)
      2.11
Leak detection
system
 Guidance section C(2) (a)/
 Section 264.302(a)(3)
      2.0
Leachate collection and   Guidance section C(2)(a)/
removal system            Section 264.301(a)(2)
                                      2.0
Final cover drain
layer
Guidance section E(2)(d)(I)/
Section 264.310(a)(b)
      2.0
Final cover low
permeability layer
Guidance section E(2)(e)(2)(A)
Section 264.310(a)(b)
      2.0
General hydrogeologic
site investigation
264 subpart F
      3.0
-/RCRA Guidance Document:  Landfill Design, Liner Systems  and
  Final Cover.  Issued July, 1982.

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                                                             1-5

Part 264 are given  in  sufficient  detail  to  provide  an
experienced hydrogeologist or geotechnical  engineer with  the
methodology required to conduct the  tests.   Additional  labora-
tory and field methods that may be applicable  under certain
conditions are included by providing reference to standard
texts and scientific journals.

Included in this report are descriptions of field methods con-
sidered appropriate for estimating saturated hydraulic  conduc-
tivity by single well  or borehole tests.  The  determination of
hydraulic conductivity by pumping or injection tests is not
included because the latter are considered  appropriate  for  well
field design purposes  but may not be appropriate for economi-
cally evaluating hydraulic conductivity  for the purposes  set
forth in part 264 Subpart F.

EPA is not including methods for  determining unsaturated
hydraulic conductivity at this time  because the Part 264  per-
mitting standards do not require  such determinations.
1.2    DEFINITIONS
This section provides definitions of terms  used in  the  remainder
of this report.  These definitions are taken from U.S.  Govern-
ment publications when possible.

1?2.1  Units;  This report uses consistent  units in all
equations.  The symbols used are:
             Length = L,
             Mass   = M, and
             Time   = T.

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                                                             1-6
1.2.2  Fluid Potential  or  head  (h)  is  a measure  of the poten-
tial energy required  to move  fluid  from a point  in the porous
medium to a reference point.  For virtually all  situations
expected to be found  in disposal sites and in ground-water
systems, h is defined by the  following equation:

          h = hp + hz                                        (1)
where
          h  is the total  fluid potential, expressed  as
             a height of fluid above a reference  datum, L;
          hp is the pressure  potential caused by  the
             weight of  fluid  above  the point in question,  L.
          hp is defined by hp = P/pg,
where
          P  is the fluid  pressure  at  the point  in question,
             ML-lT-2,
          p  is the fluid  density at the  prevailing tempera-
             ture, ML" 3,
          g  is the acceleration of gravity,  LT~2, and
          hz is the height of the point in question above
             the reference datum, L.
          By knowing hp and hz at two  points along a  flow  path
          and by knowing the  distance  between these points,
          the fluid potential gradient can be determined.

1.2.3  Hydraulic potential or head  is  the fluid potential  when
water is the fluid.
1.2.4  Hydraulic conductivity is the fluid conductivity when
water is the fluid.  The generic terra,  fluid conductity,  is
discussed below in 1.2.5.

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                                                             1-7
1.2.5  Fluid conductivity  is  defined  as  the volume of fluid at


the prevailing density  and  dynamic  viscosity that will move in


a unit time under  a  unit fluid  potential gradient through a


unit area measured at right angles  to the direction of flow.


It is a property of  both the  fluid  and the porous medium as


shown by the following  equation:
                                                             (2)
where
         K is  the  fluid conductivity,


         k  is the  intrinsic permeability,  a property of

            the porous medium  alone, L~2«


         u  is the dynamic viscosity of  the  fluid  at  the

            prevailing temperature, ML~1 T~l.



The fluid conductivity of a porous material  is  also defined by


Darcy's law, which  states that the fluid flux  (q)  through a


porous medium  is proportional  to  the first  power of the  fluid


potential across the unit area:
         q -   - KI,                                         (3)
             A


where


         q » the specific fluid  flux,  LT~1,


         Q is the volumetric  fluid  flux,  L3T-1,


         A is the cross-sectional area, L2,  and


         I is the fluid potential gradient,  L°.

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                                                             1-8

Darcy's law provides  the  basis  for  all methods  used  to  deter-
mine hydraulic conductivity discussed  in  this report.   The
range of validity of  Darcy's  law  is discussed in  Section  1.4
(Lohman, 1972).

1.2.6  Leachate conductivity  is the fluid conductivity  when
leachate is the fluid.

1.2.7  Aquifer is a geologic  formation, group of  formations, or
part of a formation capable of yielding a significant amount of
ground water to wells or  springs  (40 CFR  260.10).

1.2.8  Confining layer is a body  of impermeable material  stra-
tigraphically adjacent to one or  more aquifers.   In  nature,
however, its hydraulic conductivity may range from nearly zero
to some value distinctly  lower than that of the aquifer.  Its '
conductivity relative to  that of  the aquifer it confines  should
be specified or indicated by a suitable modifier, such  as
slightly permeable or moderately  permeable  (Lohman,  1972).

1.2.9  Transmissivity, T  [L^, T~l], is the  rate at which  water
of the prevailing kinematic viscosity is  transmitted through a
unit width of the aquifer under a unit hydraulic  gradient.
Although spoken of as a property  of the aquifer,  the term also
includes the saturated thickness  of the aquifer and  the proper-
ties of the fluid.  It is equal to an integration of the
hydraulic conductivities  across the saturated part of the
aquifer perpendicular to  the flow paths (Lohman,  1972).

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                                                             1-9
1.3    TEMPERATURE AND VISCOSITY  CORRECTIONS
By using Equation 2,  corrections  to  conditions  different from
those prevailing during  the  test  can be  made.   Two types of
corrections can commonly be  made:  a correction for a tem-
perature that varies  from the  test temperature, and a correc-
tion for fluids other than that used for the  test.  The tem-
perature correction is defined by:
         Kf
              *t "t Pf ,                                     (4)
                 Wf Pt
where
         the subscript  f  refers  to  field  conditions,  and
         t refers  to  test conditions.

Most temperature corrections  are  necessary  because  of the
viscosity dependence  on temperature.   Fluid density variations
caused by temperature changes  are usually very small  for most
liquids.  The temperature correction  for  water can  be signifi-
cant.  A temperature  decrease  from  75°C to  10°C results  in a
68 percent reduction  in viscosity and  hence hydraulic conduc-
tivity.  Equation  4 can also  be  used  to determine hydraulic
conductivity if fluids other  than water are used.   It is
assumed, however,  when using  Equation  4 that the fluids  used
do not alter the intrinsic permeability of  the porous medium
during the test.   Experimental evidence exists that shows  that
this alteration occurs with a wide  range  of organic solvents
(Anderson and Brown,  1981).  Consequently,  it is recommended

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                                                            1-10

that tests be run using fluids, such as leachates, that might
occur at each particular disposal site.  Special considerations
for using non-aqueous fluids are given in Section 3.3 of  this
report.

1.4    INTRINSIC PERMEABILITY
Rearrangement of Equation 2 results in a definition of intrin-
sic permeability.
                              .                              (5)
                          pg
Since this is a property of the medium alone, if fluid proper-
ties change, the fluid conductivity must also change to keep
the intrinsic permeability a constant.  By using measured  fluid
conductivity, and values of viscosity and density for the  fluid
at the test temperature, intrinsic permeability can be determined,

1.5    RANGE OF VALIDITY OF DARCY'S LAW
Determination of fluid conductivities using both laboratory and
field methods requires assuming the validity of Darcy's law.
Experimental evidence has shown that deviations from the linear
dependence of fluid flux on potential gradient exist for both
extremely low and extremely high gradients (Hillel, 1971;
Freeze and Cherry, 1979).  The low gradient limits are the
result of the existence of threshold gradients required to ini-
tiate flow (Swartzendruber, 1962).  The upper limits to the
validity of Darcy's law can be estimated by the requirements

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                                                            1-11
that the Reynolds number,  Re,  in most  cases  be  kept  below 10
(Bear, 1972).  The Reynolds  number  is  defined by:


            Re=^,                                       (6)
where
            d is some characteristic dimension  of  the
              system, often  represented  by  the  median  grain
              size diameter, DKQ,  (Bouwer,  1978),  and
            q is the  fluid  flux per  unit  area,  LT~1.

For most field situations,  the Reynolds number  is  less than -
one, and Darcy's law  is valid.  However,  for  laboratory tests
it may be possible to exceed  the  range of validity by the impo-
sition of high potential gradients.  A rough  check on accep-
table gradients can be made by substituting Darcy's law in
Equation 6 and using  an upper limit  of 10 for Re:
                         ,                                    (7)
                 pKDso
where
             K is the approximate value of  fluid  conductivity
               determined at gradient  I.

A more correct check on  the validity of Darcy's  law  or  the
range of gradients used  to determine fluid  conductivity would
be to measure the conductivity  at three different gradients.
If a plot of fluid flux  versus  gradient is  linear, Darcy's law
can be considered to be  valid for the  test  conditions.

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                                                            1-12





1.6    METHOD CLASSIFICATION



This report classifies methods to determine fluid conductivity



into two divisions:  laboratory and field methods.  Ideally,



compliance with the Part 264 disposal facility requirements



should be evaluated by using field methods that test  the



materials under in-situ conditions whenever possible.   In



general, field methods can usually provide more representative



values than laboratory methods because they test a larger



volume of material, thus integrating the effects of macro-



structure and heterogeneities.  However, field methods  pre-



sently available to determine the conductivity of compacted  -



fine-grained materials in reasonable times require the  tested



interval to be below a water table, to be fairly thick, or  to



require excavation of the material to be tested at some point



in the test.  The integrity of liners and covers should not be



compromised by the installation of boreholes or piezometers



required for the tests.  These restrictions generally result  in



the requirement to determine the fluid conductivity of  liner



and cover materials in the laboratory.  The transfer value  of



laboratory data to field conditions can be maximized  for liners



and covers because it is possible to reconstruct relatively



accurately the desired field conditions in the laboratory.



However, field conditions that would alter the values deter-



mined in the laboratory need to be addressed in permit  applica-



tions.  These conditions include those that would increase  con-



ductivity by the formation of microcracks and channels  by



repeated wetting and drying, and by the penetration of  roots.

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                                                            1-13





Laboratory methods are categorized  in Section  2.0 by  the



methods used to apply the fluid potential gradient  across  the



sample.  The discussion of  the theory, measurement, and com-



putations for tests run under constant and  falling-head con-



ditions is followed by a detailed discussion of  tests  using



specific types of laboratory apparatus and  the applicability of



these tests to remolded compacted,  fine-grained  uncompacted,



and coarse-grained porous media.  Section 2.3  provides a



discussion of the special considerations for conducting



laboratory tests using non-aqueous  permeants.  Section 2.10



gives a discussion of the sources of error  and guidance for -



establishing the precision  of laboratory tests.





Field methods are discussed in Section 3.0  and are  limited to



those requiring a single bore hole  or piezometer.   Methods



requiring multiple bore holes or piezometers and areal methods



are included by reference.  Because of the  difficulties in



determining fluid conductivity of in-place  liner and  cap



materials under field conditions without damaging their



integrity, the use of field methods for fine-grained  materials



will be generally restricted to naturally occurring materials



that may serve as a barrier to fluid movement.  Additional



field methods are referenced that allow determination  of



saturated hydraulic conductivity of the unsaturated materials



above the shallowest water  table.   General  methods  for frac-



tured media are given in Section 3.8.

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                                                           1-14





A discussion of the important considerations in well  installa-



tion, construction, and development is included as an introduc-



tion to Section 3.0.

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                                                             2-1


                    2.0  LABORATORY METHODS


2.1  SAMPLE COLLECTION FOR LABORATORY METHODS

To assure that a reasonable assessment  is made  of  field  con-

ditions at a disposal site, a  site investigation plan  should be

developed to direct sampling and  analysis.   This plan  generally

requires the professional judgment of an experienced hydro-

geologist or geotechnical engineer.  General guidance  is pro-

vided for plan development in  the Guidance Manual  for

Preparation of a Part 264 Land  Disposal Facility Permit

Application (EPA,  in press).   The points listed below  should

be followed:

o  The hydraulic conductivity  of  a soil liner should be  deter-
   mined either from samples that are processed to simulate
   the actual liner, or from an undisturbed  sample of  the
   complete liner.

   To obtain undisturbed samples, the thin-walled  tube sampling
   method (ASTM Method f D1587-74) or a similar method may be
   used.  Samples  representative  of each lift of the liner
   should be obtained, and used in the analyses.   If actual
   undisturbed samples are not  used, the soil used in  liner
   construction must be processed to represent  accurately
   the liner's initial water content and bulk density.   The
   method described in Section  2.7.3 or ASTM Method ID698-70
   (ASTM, 1978) can be used for this purpose.

o  For purposes of the general  site investigation,  the general
   techniques presented in ASTM method ID420-69 (ASTM, 1978)
   should be followed.  This reference establishes practices
   for soil and rock investigation and sampling, and incorporates
   various detailed ASTM procedures for investigations,  sampling,
   and material classification.


2.2  CONSTANT-HEAD METHODS

The constant-head method is the simplest method to determine

hydraulic conductivity of saturated soil samples.   The concept

of the constant-head method is  schematically illustrated in

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                                                             2-2


Figure 1.  The inflow of  fluid  is maintained  at  a constant

head  (h) above a datum and outflow  (Q)  is  measured as a func-

tion  of  time  (t).  Using  Darcy's law,  the  hydraulic conduc-

tivity can be determined  using  the  following  equation after the

outflow  rate has become constant:


               K = QL/hA,                                   (8)

where
               K = hydraulic  conductivity,  LT~1

               L = length of  sample, L

               A = cross-sectional  area of  sample, L,2

               Q = outflow rate, L^T1

               h = fluid  head difference across  the sample, L


Constant-head methods should  be restricted  to tests on media

having high fluid conductivity.



2.3   FALLING-HEAD METHODS

A schematic diagram of the apparatus for the  falling-head

method is shown in Figure 2.  The head  of  inflow fluid

decreases from hj to h2 as a  function  of time (t)  in a standpipe

directly connected to the specimen.  The fluid head at the

outflow  is maintained constant.  The quantity of outflow can be

measured as well as the quantity of inflow.   For the setup shown

in Figure 2a, the hydraulic conductivity can  be  determined

using the following equation:
                   ^_

                   At       -10 hi

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                                                         2-3
                          WATER SUPPLY
                 D
OVERFLOW
TO MAINTAIN
CONSTANT HEAD
             T
               L
                   — A-
              SCR
                 EE N—'
                                      GRADUATED
                                      CYLINDER
  Figure 1.—Principle of the constant head method

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                                                      2-4
STANDPIPE — »•
rT"


~ -^— "
*s

i
«<— d
^
v. D : :

: ; •"_•'.
i
i

h0
j
--!r=^j i

hl
1
L
OVERFLOW ^
' <^


J
r


ho
P
~=_=~ •=
7


'• o'-'
•V":v


__ ^^
            (a)
                                         (b)
                                        A -
Figure 2.—Principle of  the  falling head method
           using a  small (a)  and large (b)  standpipe.

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                                                             2-5

where
          a = the cross-sectional  area  of  the  standpipe,  L2
          A = the cross-sectional  area  of  the  specimen,  L2
          L = the length of  the  specimen,  L
          t = elapsed  time from  t^ to t2/  T.

For the setup shown in Figure  2b,  the term a/A in Equation 9 is
replaced by 1.0.  Generally, falling-head  methods are  applicable
to fine-grained soils  because  the  testing  time can be  accelerated,

2.4    GENERAL TEST CONSIDERATIONS
2.4.1  Fluid Supplies  to be  Used
For determining hydraulic conductivity  and leachate conduc-
tivity, the supplies of permeant fluid  used should be  de-aired.
Air coming out of solution in  the  sample can significantly
reduce the measured fluid conductivity.  Deairing can  be
achieved by boiling the water  supply under a vacuum, bubbling
helium gas through the supply, or  both.

Significant reductions in hydraulic conductivity  can also occur
in the growth and multiplication of microorganisms present in
the sample.  If it is  desirable  to prevent such growth,  a bac-
tericide or fungicide, such  as 2000 ppm formaldehyde or  1000 ppm
phenol (Olsen and Daniel, 1981), can be added  to  the fluid supply,

Fluid used for determining hydraulic conductivity in the  labora-
tory should never be distilled water.   Native  ground water from
the aquifer underlying the sampled area or water  prepared to
simulate the native ground-water chemistry should be used.

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                                                             2-6


2.4.2  Pressure and Fluid Potential Measurement
                              ^
The equations in this report  are all dimensionally  correct;

that is, any consistent set of units may be used  for  length,

mass, and time.  Consequently, measurements of pressure  and/or

fluid potential using pressure gages and manometers must be

reduced to the consistent units used before applying  either

Equation 8 or 9.  Pressures or potentials should  be measured

to within a few tenths of one percent of the gradient applied

across the sample.



2.5    CONSTANT-HEAD TEST WITH CONVENTIONAL PERMEAMETER

2.5.1  Applicability

This method covers the determination of the hydraulic conduc-

tivity of soils by a constant-head method using a conventional

permeameter.  This method is  recommended for disturbed coarse-

grained soils.  If this method is to be used for  fine-grained

soils, the testing time may be prohibitively long.  This method

was taken from the Engineering and Design, Laboratory Soils

Testing Manual (U.S. Army, 1980).  It parallels ASTM  Method

D2434-68 (ASTM, 1978).  The ASTM method gives extensive

discussion of sample preparation and applicability  and should

be reviewed before conducting constant-head tests.  Lambe (1951)

provides additional information on sample preparation and

equipment procedures.

-------
                                                             2-7


2.5.2  Apparatus

The apparatus is shown schematically  in  Figure  3.   It  consists

of the following:


   a.   A permeameter cylinder  having  a  diameter  at least
        8 times the diameter of the largest  particle of  the
        material to be tested,

   b.   Constant-head filter tank,

   c.   Perforated metal disks  and circular  wire  to support
        the sample,

   d.   Filter materials such as Ottawa  sand, coarse sand, and
        gravel of various gradations,

   e.   Manometers connected to the top  and  bottom  of  the sample,

   f.   Graduated cylinder, 100 ml capacity,

   g.   Thermometer,

   h.   Stop watch,

   i.   Deaired water,

   j.   Balance sensitive to 0.1 gram, and

   k.   Drying oven.



2.5.3  Sample Preparation

1.  Oven-dry the specimen.  Allow it to  cool, and weigh  to the
    nearest 0.1 g.  Record the  oven-dry  weight  of material on  a
    data sheet as Ws.  The amount of material should be  sufficient
    to provide a specimen in the permeameter having a  minimum
    length of about one to two  times the diameter of the  specimen.

2.  Place a wire screen, with openings small enough to retain
    the specimen, over a perforated disk near the bottom  of  the
    permeameter above the inlet.  The  screen openings  should be
    approximately equal to the  10 percent size  of the  specimen.

3.  Allow deaired water to enter the water inlet of the
    permeameter to a height of  about 1/2 in. above  the bottom
    of the screen, taking care  that no air bubbles  are trapped
    under the screen.

-------
                                                                        2-8
                    Conttant
                   Heed Tenk
     Screen
 Perforated
O Ite & Screen
                    -=• Cylinder
1
ted
r
;••-


1
•
V alve
A|-
=?>
Standplpe
C.^,
I1
If
e ]
.
^
S
•«
V
H
-
Fl
M t
creen.
live
B
                                                     De - Aired
                                                     Water Supply
                                                         Therm o- '
                                                   F liter [\ m eter

                                                                 D Iteherge
                                                              A  Level
                                                              Witt*
                          Perforated
                          O lie & Scraar
            Ca)
      constant head
Watte
      (b)
falling head
   Figure  3.— Apparatus setup for the  constant head (a)
                 and falling  head  (b)  methods.

-------
                                                             2-9

4.  Mix the material thoroughly and place  in  the permeameter to
    avoid segregation.  The material should be dropped  just  at
    the water surface/ keeping the water surface about  1/2  in.
    above the top of the soil during placement.  A  funnel or a
    spoon is convenient for this purpose.

5.  The placement procedure outlined above will result  in a
    saturated specimen of uniform density  although  in a rela-
    tively loose condition.  To produce a  higher density in  the
    specimen, the sides of the permeameter containing the soil
    sample are tapped uniformly along  its  circumference and
    length with a rubber mallet to produce an increase  in
    density; however, extreme caution  should  be exercised so
    that fines are not put into suspension and segregated
    within the sample.  As an alternative  to  this procedure,
    the specimen may be placed using an appropriate  sized
    funnel or spoon.  Compacting the specimen in layers is
    not recommended as a film of dust  may  be  formed  at  the
    surface of the compacted layer which might affect the
    permeability results.  After placement, apply a  vacuum
    to the top of the specimen and permit  water to  enter the
    evacuated specimen through the base of the permeameter.

6.  After the specimen has been placed, weigh the excess
    material, if any, and the container.   The specimen  weight
    is the difference between the original weight of sample  and
    the weight of the excess material.  Care must be taken so
    that no material is lost during placement of the specimen.
    If there is evidence that material has been lost, oven-dry
    the specimen and weigh after the test  as  a check.

7. -Level the top of the specimen, cover with a wire screen
    similar to that used at the base,  and  fill the  remainder of
    the permeameter with a filter material.

8.  Measure the length of the specimen, inside diameter of the
    permeameter, and distance between  the  centers of the
    manometer tubes (L) where they enter the permeameter.


2.5.4  Test Procedure

1.  Adjust the height of the constant-head tank to obtain the
    desired hydraulic gradient.  The hydraulic gradient should
    be selected so that the flow through the specimen is lami-
    nar.   Hydraulic gradients ranging  from 0.2 to 0.5 are recom-
    mended.  Too high a hydraulic gradient may cause turbulent
    flow and also result in piping of  soils.  In general,
    coarser soils require lower hydraulic gradients.  See
    Section 1.5 for further discussion of excessive  gradients.

2.  Open valve A (see Figure 3a) and record the initial
    piezometer readings after the flow has become stable.
    Exercise care in building up heads in  the permeameter
    so that the specimen is not disturbed.

-------
                                                            2-10
3.  After allowing a few minutes  for equilibrium conditions to
    be reached, measure by means  of a graduated cylinder  the
    quantity of discharge corresponding  to a given  time  inter-
    val.  Measure the piezometric heads  (hi and h2)  and  the
    water temperature in the permeameter.
4.  Record the quantity of flow,  piezometer readings, water
    temperature, and the time  interval during which  the quan-
    tity of flow was measured.

2.5.5  Calculations
By plotting the accumulated quantity of  outflow versus time on
rectangular coordinate paper,  the slope  of the linear portion
of the curve can be determined, and the  hydraulic conductivity
can be calculated using Equation  (8).  The value of  h in
Equation 8 is the difference between hj  and h2«

2.6    FALLING-HEAD TEST WITH  CONVENTIONAL PERMEAMETER
2.6.1  Applicability
The falling-head test can be used for all soil types, but is
usually most widely applicable to materials having low per-
meability.  Compacted, remolded,  fine-grained soils  can be  tested
with this method.  The method  presented  is taken from the
Engineering and Design, Laboratory Soils Testing Manual  (U.S.
Army, 1980).

2.6.2  Apparatus
The schematic diagram of falling-head permeameter is shown  in
Figure 3b.  The permeameter consists of  the following equipment:
   (1)  Permeameter cylinder - a  transparent acrylic cylinder
        having a diameter at least 8 times the diameter of  the
        largest particles,
   (2)  Porous disk,

-------
                                                            2-11
   (3)  Wire screen,

   (4)  Filter materials,

   (5)  Manometer,

   (6)  Timing device,  and

   (7)  Thermometer.


2.6.3  Sample Preparation

Sample preparation  for  coarse-grained  soils  is  similar to that

described previously  in Section  2.4.3.   For  fine-grained

soils, samples are  compacted  to  the  desired  density using

methods described in  ASTM Method D698-70.


2.6.4  Test Procedure

1.  Measure and record  the height of the specimen,  L,  and the
    cross-sectional area of the  specimen,  A.

2.  With valve B open  (see Figure 3b),  crack valve  A,  and slowly
    bring the water level up  to  the  discharge level of the
    permeameter.

3.  Raise the head of water in the standpipe above  the
    discharge level of  the permeameter.   The difference in head
    should not result in an excessively high hydraulic gradient
    during the test.  Close valves A and B.

4.  Begin the test by opening valve  B.   Start the  timer.  As
    the water flows through the  specimen,  measure  and  record
    the height of water in the standpipe above  the  discharge
    level, h]_, at time  ti, and the height  of water  above the
    discharge level,  h£ at time  t£.

5.  Observe and record  the temperature  of  the water in the
    permeameter.


2.6.5  Calculations
From the test data, plot the logarithm of  head  versus  time,  on

rectangular coordinate paper or use semi-log  paper.  The  slope

of the linear part of the- curve is used  to determine

-------
                                                            2-12

                 Calculate the hydraulic conductivity  using
Equation  (9) .
2.7    MODIFIED COMPACTION PERMEAMETER METHOD
2.7.1  Applicability
This method can be used to determine  the hydraulic  conductivity
of a wide range of materials.  The method  is generally  used  for
remolded fine-grained soils.  The method is generally used under
constant-head conditions.  The method was  taken  from Anderson
and Brown, 1981, and EPA  (1980).

2.7.2  Apparatus
The apparatus is shown in Figure 4 and consists  of  the  equip-
ment and accessories as follows:
   a.   Soil Chamber - A compaction mold having a diameter
        8 times larger than the diameter of the largest
        particles.  Typically, ASTM standard mold (Number CN405)
        is used,
   b.   Fluid Chamber - A compaction mold sleeve having  the
        same diameter as the soil chamber,
   c.   2 kg hammer,
   d.   Rubber rings used for sealing purposes,
   e.   A coarse porous stone having higher permeability than
        the tested sample,
   f.   Regulated source of compressed air, and
   g.   Pressure gage or manometer to determine the pressure
        on the fluid chamber.
2.7.3  Sample preparation
1.  Obtain sufficient representative soil sample.  Air  dry  the
    sample at room temperature.  Do not oven dry.

-------
                                                            2-13
(2).  Thoroughly mix  the  selected  representative  sample with
      water to obtain a desired moisture  content.
(3).  Compact the sample  to  the desired density within the
      mold using the method  described  as  part  of  ASTM Method
      D698-70.
(4).  Level the surface of the compacted  sample with  straight
      edge, weigh and determine the  density  of the  sample.
(5).  Measure the length  and diameter  of  the sample.
(6).  Assemble the apparatus, make sure that there  are no
      leaks, then connect the pressure line  to the  apparatus.
2.7.4  Test Procedure
(1).  Place sufficient volume of water in the  fluid chamber
      above the soil chamber.
(2).  Air pressure must be applied gradually to flush water  ,
      through the sample  until no  air  bubbles  in  the  outflow
      are observed.  For  fine-grained  soils, the  saturation
      may take several hours to several days,  depending on
      the applied pressure.
(3).  After the sample is saturated, measure and  record the
      quantity of outflow versus time.
(4).  Record the pressure reading  (h)  on  the top  of the fluid
      chamber when each reading is made.
(5).  Plot the accumulated quantity  of outflow versus time on
      rectangular coordinate paper.
(6).  Stop taking readings as soon as  the linear  portion of
      the curve is defined.
2.7.5  Calculations
The hydraulic conductivity can be calculated  using  Equation  8.

2.8    TRIAXIAL-CELL METHOD WITH BACK  PRESSURE
2.8.1  Applicability
This method is applicable for all soil types, but especially
for fine-grained, compacted, cohesive  soils in which  full  fluid
saturation of the sample is difficult  to achieve.   Normally,
the test is run under, constant-head conditions.

-------
                                                               2-14
                         TO REGULATED PRESSURE SOURCE AND
                         PRESSURE GAGE OR MANOMETER USED TO
                         MEASURE H .
                                PRESSURE RELEASE VALVE

                                        £*	TOP PLATE
                                              RUBBER "0" RING SEALS
                                              BASE PLATE
                              OUTFLOW TO VOLUMETRIC MEASURING DEVICE.

                              PRESSURE SHOULD BE ATMOSPHERIC OR ZERO
                              GAGE PRESSURE
Figure  4.—Modified compaction permeameter.
            Note: h in  Equation 8 is  the difference
            between the regulated inflow pressure
            and the outflow pressure.   Source:
            Anderson and Brown, 1981.

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                                                           2-15


2.8.2  Apparatus

The apparatus is similar to conventional  triaxial  apparatus.

The schematic diagram of this apparatus is  shown in  Figure  5.



2.8.3  Sample Preparation

Disturbed or undisturbed samples can be tested.  Undisturbed

samples must be trimmed to the diameter of  the  top cap  and

base of the triaxial cell.  Disturbed samples should  be prepared

in the mold using either kneading compaction for fine-grained

soils, or by the pouring and vibrating method for  coarse-grained

soils, as discussed in Section 2.5.3.



2.8.4  Test Procedure


(1).  Measure the dimensions and weight of  the  prepared sample.


(2).  Place one of the prepared specimens on the base.


(3).  Place a rubber membrane in a membrane stretcher,  turn
      both ends of the membrane over the ends of the  stretcher,
      and apply a vacuum to the stretcher.  Carefully lower the
      stretcher and membrane over the specimen  as  shown in
      Figure 9.  Place the specimen cap on  the  top of the
      specimen and release the vacuum on the membrane stretcher.
      Turn the ends of the membrane down around the  base and
      up around the specimen cap and fasten the ends  with O-rings,

(4).  Assemble the triaxial chamber and place it in  position in
      the loading device.  Connect the tube from the  pressure
      reservoir to the base of the triaxial chamber.  With
      valve C (see Figure 5) on the pressure reservoir  closed
      and valves A and B open, increase the pressure  inside the
      reservoir, and allow the pressure fluid to fill the
      triaxial chamber.  Allow a few drops of the  pressure  fluid
      to escape through the vent valve (valve B) to  insure
      complete filling of the chamber with  fluid.  Close valve A
      and the vent valve.

-------
                                                         2-16
Figure 5.-
-Schematic diagram of typical triaxial compression
 apparatus for hydraulic conductivity tests with
 back pressure.
 Source: U.S. Army Corps of Engineers, 1970

-------
                                                           2-17

(5).  Place saturated filter paper disks having the same
      diameter as that of the specimen between the specimen and
      the base and cap; these disks will also facilitate remo-
      val of the specimen after the test.  The drainage lines
      and the porous inserts should be completely saturated
      with deaired water.  The drainage lines should be as
      short as possible and made of thick-walled, small-bore
      tubing to insure minimum elastic changes in volume due to
      changes in pressure.  Valves in the drainage lines
      (valves E, F, and G in Figure 5) should preferably be of
      a type which will cause no discernible change of internal
      volume when operated.  While mounting the specimen in the
      compression chamber, care should be exercised to avoid
      entrapping any air beneath the membrane or between the
      specimen and the base and cap.

(6).  Specimens should be completely saturated before any
      appreciable consolidation is permitted, for ease and
      uniformity of saturation, as well as to allow volume
      changes during consolidation to be measured with the
      burette; therefore, the difference between the chamber
      pressure and the back pressure should not exceed 5 psi -
      during the saturation phase.  To insure that a specimen
      is not prestressed during the saturation phase, the back
      pressure must be applied in small increments, with ade-
      quate time between increments to permit equalization of
      pore water pressure throughout the specimen.

(7).  With all valves closed, adjust the pressure regulators to
      a chamber pressure of about 7 psi and a back pressure of
      about 2 psi.  Now open valve A to apply the preset
      pressure to the chamber fluid and simultaneously open
      valve F to apply the back pressure through the specimen
      cap.  Immediately open valve G and read and record the
      pore pressure at the specimen base.  When the measured
      pore pressure becomes essentially constant, close valves
      F and G and record the burette reading.

(8).  Using the technique described in step (3), increase the
      chamber pressure and the back pressure in increments,
      maintaining the back pressure at about 5 psi less than
      the chamber pressure.  The size of each increment might
      be 5, 10, or even 20 psi, depending on the compressibi-
      lity of the soil specimen and the magnitude of the
      desired consolidation pressure.  Open valve G and measure
      the pore pressure at the base immediately upon applica-
      tion of each increment of back pressure and observe the
      pore pressure until it becomes essentially constant.  The
      time required for stabilization of the pore pressure may
      range from a few minutes to several hours depending on
      the permeability of the soil.  Continue adding increments
      of chamber pressure and back pressure until, under any
      increment, the pore pressure reading equals the applied
      back pressure immediately upon opening valve G.

-------
                                                            2-18


 (9).   Verify the completeness of saturation by closing valve
        F and increasing the chamber pressure by about 5 psi.
        The specimen shall not be considered completely
        saturated unless the increase in pore pressure imme-
        diately equals the increase in chamber pressure.


(10).   When the specimen is completely saturated, increase the
        chamber pressure with the drainage valves closed to
        attain the desired effective consolidation pressure
        (chamber pressure minus back pressure).  At zero
        elapsed time, open valves E and F.


(11).   Record time, dial indicator reading, and burette
        reading at elapsed times of 0, 15, and 30 sec, 1, 2, 4,
        8, and 15 rain, and 1, 2, 4, and 8 hr, etc.  Plot the
        dial indicator readings and burette readings on an
        arithmetic scale versus elapsed time on a log scale.
        When the consolidation curves indicate that primary
        consolidation is complete, close valves E and F.


(12).   Apply a pressure to burette B greater than that in
        burette A.  The difference between the pressures in
        burettes B and A is equal to the head loss (h); h divided
        by the height of the specimen after consolidation (L)
        is the hydraulic gradient.  The difference between  the
        two pressures should be kept as small as practicable,
        consistent with the requirement that the rate of flow
        be large enough to make accurate measurements of the
        quantity of flow within a reasonable period of time.
        Because the difference in the two pressures may be very
        small in comparison to the pressures at the ends of the
        specimen, and because the head loss must be maintained
        constant throughout the test, the difference between
        the pressures within the burettes must be measured
        accurately; a differential pressure gage is very useful
        for this purpose.  The difference between the eleva-
        tions of the water within the burettes should also be
        considered (1 in. of water = 0.036 psi of pressure).


(13).   Open valves D and F.  Record the burette readings at
        any zero elapsed time.  Make readings of burettes A and
        B and of temperature at various elapsed times (the
        interval between successive readings depends upon the
        permeability of the soil and the dimensions of the
        specimen).  Plot arithmetically the change in readings
        of both burettes versus time.  Continue making readings
        until the two curves become parallel and straight over
        a sufficient length of time to determine accurately the
        rate of flow as indicated by the slope of the curves.

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                                                            2-19

2.8.5  Calculations
The hydraulic conductivity  can  be  calculated  using  Equation 8.


2.9    PRESSURE-CHAMBER  PERMEAMETER METHOD
2.9.1  Applicability
This method can be used  to  determine hydraulic  conductivity of
a wide range of soils.   Undisturbed and  disturbed  samples  can
be tested under falling-head  conditions  using this  method.
This method is also applicable  to  both coarse-  and  fine-grained
soils, including remolded,  fine-grained  materials.

2.9.2  Apparatus
The apparatus, as shown  in  Figure  6,  consists of
       a.  pressure chamber,
       b.  standpipe,
       c.  specimen cap  and base,  and
       d.  coarse porous plates.
The apparatus is capable of applying confining  pressure  to
simulate field stress conditions.

2.9.3  Sample Preparation
The sample preparation of disturbed and  undisturbed conditions
can be prepared in the chamber  and  enclosed within  the rubber
membrane, as discussed in Section  2.8.4.

-------
                                                    2-20
     -HVtLIMC »ULi
             mint*
  NOTCCOWMCMIO AM U»€0
     MICMtH LATIMAt
     M M.ACI 0^ LCVtLINC «Uk»
Figure 6.-
-Pressure chamber for  hydraulic
 conductivity.
 Source: U.S.  Army Corps of Engineers,
 1980.

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                                                            2-21


2.9.4  Test Procedure

(1).   By adjusting  the  leveling bulb,  a  confining  pressure is
       applied to the sample  such  that  the  stress conditions
       represent field conditions.   For higher  confining
       pressure, compressed air may  be  used.

(2).   Allow the sample  to consolidate  under  the applied  stress
       until the end of  primary consolidation.

(3).   Flush water through the sample until no  indication of
       air bubbles is observed.  For higher head of water,
       compressed air may be  used.

(4).   Adjust the head of water to attain a desired hydraulic
       gradient.

(5).   Measure and record the head drop in  the  standpipe  along
       with elapsed  time until the plot of  logarithm of head
       versus time is linear  for more than  three consecutive
       readings.



2.9.5  Calculations

The hydraulic conductivity can be determined  using  Equation 9.




2.10   SOURCES OF ERROR  FOR LABORATORY  TEST FOR HYDRAULIC
       CONDUCTIVITY

There are numerous potential  sources of error in laboratory

tests for hydraulic  conductivity.  Table  B  summarizes some

potential errors that can occur.  Olson and Daniel  (1981)  pro-

vide a more detailed explanation of  sources of  these errors and

methods to minimize  them.  If the hydraulic conductivity  does

not fall within the expected  range for  the  soil type, as  given

in Table C, the measurement should be repeated  after checking

the source of error  in Table  B.

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                                                           2-22
                            TABLE B

         SUMMARY OF PUBLISHED DATA ON POTENTIAL ERRORS
                      IN USING DATA FROM
       LABORATORY PERMEABILITY TESTS ON SATURATED SOILS
     Source of Error and References
     Measured K
Too Low or Too High?
 1.  Voids Formed in Sample Preparation
     (Olson and Daniel, 1981).

 2.  Smear Zone Formed During Trimming
     (Olson and Daniel, 1981).

 3.  Use of Distilled Water as a
     Permeant (Fireman, 1944; and
     Wilkinson, 1969).

 4.  Air in Sample (Johnson, 1954).

 5.  Growth of Micro-organisms
     (Allison, 1947).

 6.  Use of Excessive Hydraulic
     Gradient (Schwartzendruber, 1968;
     and Mitchell and Younger, 1967).

 7.  Use of temperature other than the
     test temperature.

 8.  Ignoring Volume Change Due to
     Stress Change.  (No confining
     pressure used).

 9.  Performing Laboratory Rather
     than In-Situ Tests (Olson and
     Daniel, 1981).

10.  Impedance caused by the test
     apparatus, including the
     resistance of the screen or
     porous stone used to support
     the sample.
        High


        Low



        Low

        Low


        Low



     Low or High


       Varies



       High



     Usually low
       Low

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                                                            2-23
2.11  LEACHATE CONDUCTIVITY USING LABORATORY METHODS



Many primary and secondary leachates  found  at disposal  sites



may be nonaqueous liquids or aqueous  fluids of  high  ionic



strength.  These fluids may significantly alter the  intrinsic



permeability of the porous medium.  For example, Anderson  and



Brown (1981) have demonstrated  increases in hydraulic conduc-



tivity of compacted clays of as much  as two orders of magnitude



after the passage of a few pore volumes of  a wide range of



organic liquids.  Consequently, the effects of  leachate on these



materials should be evaluated by laboratory testing.  The  pre-



ceding laboratory methods can all be  used to determine  leachate



conductivity by using the following guidelines.








2.11.1  Applicability



The determination of leachate conductivity  may  be required for



both fine-grained and coarse-grained  materials.  Leachates may



either increase or decrease the hydraulic conductivity.



Increases are of concern for compacted clay liners,  and



decreases are of concern for drain materials.   The applicability



sections of the preceding methods should be used for selecting



an appropriate test for leachate conductivity.   The  use of the



modified compaction method (Section 2.7) for determining leachate



conductivity is discussed extensively in EPA Publication SW870



(EPA 1980).

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                                                              2-24


2.11.2  Leachate Used


A supply of leachate must be ootained that is as close in chemi-


cal and physical properties to the anticipated leachate at the


disposal site as possible.  Methods for obtaining such leachate


are beyond the scope of this report.   However, recent publications


by EPA (1980, SW-87U; 1982, SW-846) and Conway and Malloy (1981)


discuss methodologies for simulating the leaching environment


to obtain such leachate.  Procedures for deairing the leachate


supply are given in Section 2.4.  The importance of preventing


bacterial growth in leachate tests will depend on the expected


conditions at the disposal site.  The chemical and physical


properties that may result in corrosion, dissolution, or


encrustation of laboratory hydraulic conductivity apparatus


should be determined prior to conducting a leachate conductivity
                                                           *-  ~

test.   Properties of particular importance are the pH and the


vapor pressure of the leachate.  Both extremely acidic and


basic leachates may corrode materials.   In general, apparatus


for leachate conductivity tests should be constructed of inert


materials, such as acrylic plastic, nylon, or teflon.  Metal


parts that might come in contact with the leachate should be


avoided.   Leachates with high vapor pressures may require


special treatment.  Closed systems for fluid supply and pressure


measurement, such as those in the modified triaxial cell methods,


should be used.




2.11.3  Safety


Tests involving the use of leachates should be conducted under


a vented hood, and persons conducting the tests should wear

-------
                                                            2-25
appropriate protective clothing and eye protection.   Standard
laboratory safety procedures such as  those  as given  by
Manufacturing Chemists Association  (1971) should be  followed.

2.11.4  Procedures
The determination of leachate conductivity  should  be  conducted
immediately following the determination of  hydraulic  conduc-
tivity (Anderson and Brown, 1981).  This procedure maintains
fluid saturation of the sample, and allows  a comparison  of  the
leachate and hydraulic conductivities under the same  test
conditions.  This procedure requires modifications of test
operations as described below.

2.11.5  Apparatus
In addition to a supply reservoir for water as shown  in  Figures
3 through 6, a supply reservoir for leachate is required.
Changing the inflow to the test cell from water to leachate can
be accomplished by providing a three-way valve in  the inflow
line that is connected to each of the reservoirs.

2.11.6  Measurements
Measurements of fluid potential and outflow rates  are the same
for leachate conductivity and hydraulic conductivity.  If the
leachate does not alter the intrinsic permeability of the
sample, the criteria for the time required  to take measurements
is the same for leachate conductivity tests as for hydraulic
conductivity tests.  However, if significant changes  occur  in
the sample by the passage of leachate, measurements should be

-------
                                                            2-26
taken until either the shape of a conductivity versus pore
volume curve can be defined, or until the leachate conductivity
exceeds the applicable design value for hydraulic conductivity.
2.11.7  Calculations
If the leachate conductivity approaches a constant value,
Equations 8 and 9 can be used. If the conductivity changes  con-
tinuously because of the action of the leachate, the following
modifications should be made.  For constant-head tests,  the
conductivity should be determined by continuing a plot of
outflow volume versus time for the constant rate part of the
test conducted with water.  For falling-head tests/ the  slope
of the logarithm of head versus time should be continued.

If the slope of either curve continues to change after the  flow
of leachate begins, the leachate is altering the intrinsic  per-
meability of the sample.  The leachate conductivity in this
case is not a constant.  In this case, values of the slope  of
the outflow curve to use in Equation 8 or 9 must be taken as
the tangent to the appropriate outflow curve at the times of
measurement.

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                                                            3-1
                       3.0  FIELD METHODS



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.  However, if field tests are run with leachate or

other fluids, the methods are equally applicable.


The location of wells, selection of screened intervals,  and the

appropriate tests that are to be conducted depend upon the spe-

cific site under investigation.  The person responsible  for

such selections should be a qualified hydrogeologist or

geotechnical engineer who is experienced in the application of

established principles of contaminant hydrogeology and ground

water hydraulics.  The following are given as general guidelines.


(1).   The bottom of the screened interval should be below the
       lowest expected water level.

(2).   Wells should be screened in the lithologic units  that
       have the highest probability of either receiving
       contaminants or conveying them down gradient.

(3).   Wells up gradient and down gradient of sites should be
       screened in the same lithologic unit.


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).

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                                                             3-2

The success of field methods in determining hydraulic conduc-
tivity is often determined by the design, construction,  and
development of the well or borehole used for the tests.
Details of these methods are beyond the scope of this report;
however, important considerations are given in Sections  3.1
and 3.2.  Detailed discussions of well installation, construc-
tion, and development methods are given by Bouwer  (1978),
pages 160-180, Acker (1974), and Johnson (1972).

The methods for field determination of hydraulic conductivity
are restricted to well or piezometer type 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 and methods
which are beyond the scope of this report.

3.1    WELL-CONSTRUCTION CONSIDERATIONS
The purpose of using properly constructed wells .for hydraulic
conductivity testing is to assure that test results reflect
conditions in the materials being tested, rather than the con-
ditions caused by well construction.  In all cases, diagrams
showing all details of the actual well or borehole constructed
for the test should be made.

3.1.1  Well Installation Methods
Well installation methods are listed below in order of pre-
ference for ground-water testing and monitoring.  The order  was
determined by the need to minimize side-wall plugging by

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                                                             3-3
drilling fluids and  to maximize  the  accurate  detection  of
saturated zones.  This order  should  be  used as  a  guide,  com-
bined with the judgment of  an experienced  hydrogeologist in
selecting a drilling method.   The  combined uses of  wells for
hydraulic conductivity testing,  water-level monitoring,  and
water-quality sampling for  organic contaminants were  considered
in arriving at the ranking.

    a.  Hollow-stem  auger,
    b.  Cable tool,
    c.  Air rotary,
    d.  Rotary drilling with  non-organic drilling fluids,
    e.  Air foam rotary, and
    f.  Rotary with  organic based  drilling fluids.

Although the hollow  stem-auger method is usually  preferred  for
the installation of  most shallow wells  (less  than 100 feet),
care must be taken if the tested zone is very fine.   Smearing
of the borehole walls by drilling  action can  effectively seal
off the borehole from the adjacent formation.   Scarification
can be used to remedy this.
3.1.2  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.  Generally an inert  plastic  such as  PVC  is
preferred for ground-water  contamination studies.   The  screen
slot size should be determined to  minimize the  inflow of fine-

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                                                             3-4
grained material  to  the well  during  development  and  testing.
Bouwer (1978),  and Johnson  (1972) 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.
Guidelines for  sizing  these materials are given  by Johnson
(1972).  For very coarse materials,  it  may be  acceptable  to
allow the materials  from the  tested  zone  to  collapse around
the screen forming a natural  gravel  pack.

The screened interval  should  be isolated  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  next higher screened  interval (in  the  case
of multiple screen wells), or to the land surface for  single
screen wells.
Although considerations for sampling may dictate minimum casing
and screen diameters,  the recommended guideline  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 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

-------
                                                             3-5
while enabling  the  efficient  sudden withdrawal of water for
these tests.
3.1.3  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
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  tests are to be run.  In these
cases, the zones  of interest  can be isolated by the use of
inflatable packers.

3.2  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
bailing.   Adequate  development is  required to assure maximum
communication between fluids  in  the borehole and the zone to be
tested.   Results  from tests run  in wells that are inadequately

-------
                                                             3-6
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)
and Johnson (1975) give further details on well development
including methods to determine when adequate development  has
occurred.

3.3  DATA INTERPRETATION AND TEST SELECTION CONSIDERATIONS
Hydraulic conductivity may be determined in wells  that are
either cased or uncased as described in Section 3.1.  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).

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.

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                                                            3-7
The equations given  for all computational methods  given 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 primary use of hydraulic conductivity data from  tests
described subsequently will usually  be  to aid  in siting moni-
toring wells for facility design as  well  as  for compliance with
Subpart F of Part 264.  As such, the methods are abbreviated to
provide guidance in determining  hydraulic conductivity only.
Additional analyses  that may be  possible with  some methods to
define the storage properties of the aquifer are not included.
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
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.

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                                                             3-8
3.4  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 cm2/sec (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.
3.4.1    Method for Moderately Permeable Formations  Under
         Confined Conditions
3.4.1.1  Applicability.  This method  is applicable  for  testing
zones to which the entire zone  is open to  the well  screen or
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.

-------
                                                             3-9
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 7 illustrates  the  test  geometry for  this method.

3.4.1.2  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 (Lehman, 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

-------
                                                        3-10
Figure 7.—Geometry and variable definition for
           slug tests in confined aquifers.

-------
                                                            3-11

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.

3.1.1.3  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  (t)  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 Appendix A 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:
                                                            (10)
       where rc is the radius of the casing  (Lohman,  1972,  p.  29)

-------
                                                            3-12





       The type curves plotted using data in Appendix A  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 3.4.1.4 -



       for further discussion of the storage coefficient.





       If the data in Appendix A are used, a type curve  for



       each value of a is prepared by plotting F(a,6)  on the



       arithmetic scale and dimensionless time (3)  on the



       logarithmic scale of semi-log paper.





   b.  Determine the hydraulic conductivity by dividing  the



       transmissivity by the thickness of the tested zone.







3.4.1.4  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

-------
                                                            3-13


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 an  accuracy  of

at least 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 a, 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 o  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.


3.4.2    Methods For Extremely Tight Formations  Under
         Confined Conditions

3.4.2.1  Applicability.  This  test is  applicable to  materials

that have low to extremely low permeability such as  silts,

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                                                            3-14





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.







3.4.2.2  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 8.  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.  Neuzil's 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.





3.4.2.3  Calculations.  The modified slug test as developed by



Bredehoeft and Papadopulos (1980) considered compressive



storage of water in the borehole.  These authors  considered



that the volume of the packed-off borehole did not change

-------
                                                             3-15
  Pressure Gage
                   Valve

                    5=
                                                    V alve
     System Filled
     with Water -*.
                      - Pump


                      •Land Surface-
                              Initial Head
                    	?	 ?-jn Testec
                    Casing     Interval
                            _: Tight
                ?•*
r_-Well PointT
— ---___-—-]
                      T    -
                      Tested -^-_
•ssure Gage(/)=
ad
	 ? 	 ? -

on._^. 	
	

	


System Filled
_with Water
_ -p _____ p 	
Open Hole
-"Packer-
	
._ 	 .
. Interval to- —
"be Tested —
.J-. 	
Pump
                (a)
                                        (b)
Figure 8.—Schematic diagram for  pressurized slug
             test method in  unconsolidated  (a) and
             consolidated  (b)  materials.  Source:
             Papadopulos and Bredehoeft, 1980.

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                                                            3-16
during the test and that all compressive storage  resulted  in
compression of water under the pressure pulse.  Neuzil  (1980)
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  Appendix  A
as described in Section 3.1.1.3.  The value of  time (t) and
dimensionless time, (3), are determined in the same manner as
for the conventional tests.  If compression of water  only  is
considered, transmissivity is computed by replacing rc^ by the
quantity (Vy Crf> gA)  in Equation 10:
          =  3(VW Cw
where

       Vw is the volume of water in the packed-off  cavity,  L3;
       Cw is the compressibility of water, LT^M"!,
        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

-------
                                                            3-17
pressurization  (Av) and the pressure change AP for the

press urizat ion:

(Neuzil, 1982, page 440).  Use of  Co  requires  an  accurate  method

of metering the volume of water  injected  and  the  volume  of the

cavity.


3.4.2.4  Sources of Error.  The  types of  errors in  this  method

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).



3.4.3    Methods for Moderately  Permeable Materials Under
         Unconfined Conditions

3.4.3.1  Applicability.  This method  is applicable  to  wells

that fully or partially penetrate  the interval of interest

(Figure 9).  The hydraulic conductivity determined  will  be

principally the value in the horizontal direction (Bouwer  and

Rice, 1976.).


3.4.3.2  Procedures.  A general  method for  testing  cased wells

that partly or fully penetrate aquifers that  have a water  table

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                                                                   3-18
              WELL CASING
WELL SEAL
   Lw
        L«
                    -^
51  "iV
l>-1      ft!
                     i::--3
 GRAVEL PACK
                               Lw




                               V
                               L«

                                                    Lw
                                                                      STATIC WATER
                                                                         LEVEL
                                                  IMPENETRABLE STRATUM ^'
 (a) CASED WITH SCREEN
              (b) CASED, NO SCREEN, NO

                 CAVITY ENLARGEMENT
(c) OPEN BOREHOLE
  Figure 9.—Variable definitions for  slug tests in

              unconfined  materials. Cased wells are

              open at the bottom.

-------
                                                            3-19

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  9.  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 4.4.1.2.  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.

3.4.3.3  Calculations.  The hydraulic conductivity is calcu-
lated using the following equation in the notation of this
report, taken from Bouwer and Rice (1976)

             rc  In R/r   ,   y
               2 Let~Y

where rc, rw, Le, t, Y, and K have been  previously defined  or
are defined in Figure 8a.  Yo is 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).
     ln
        rw      In (Lw/rw

-------
                                                            3-20





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:
      in*-  =(_	I-*    .  + —-£_)   ,                   (14)
          •w
In (Lw/rw)    Le/rw
(Bouwer, 1976).  The values of  the constants A, B,  and  C are



given by Figure 10  (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 9b and 9c.)





3.4.3.4  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



3.4.1.4 and 3.4.2.4.

-------
                                                       3-21
   14
A
and
C
  12
  10
   2-
                10
           50  100
500  IOOO
                                                      B
                                            L/r.
                                                5OOO
 Figure 10.
—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.

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                                                           3-22


3.5    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 tests discussed in Section 4.4.  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).
3.6  ESTIMATES OF HYDRAULIC CONDUCTIVITY FOR COARSE-GRAINED
     MATERIALS

To characterize the ground-water flow system to satisfy  the

intent of Part 264 Subpart F, estimates of  the hydraulic con-

ductivity based on grain-size analyses or visual grain-size

classification may be appropriate.  However, hydraulic conduc-

tivities determined by these methods are not to be  used  in per-

mit applications.  Several theoretical models are available  to

provide these estimates, with one of most widely used being

-------
                                                            3-23
Kozeny-Carmen equation which defines the intrinsic permeability,
as adapted from Bear  (1972):
          k . _!»L_  I^L.  ,                                (15)
              (l-n)2  180
where n is the effective porosity, and all other terms are as
previously defined.

An empirical approach that has been used by the U.S. Geological
Survey (Lappala, 1978) in several studies relates conductivity
determined by aquifer testing to grain-size, degree of sorting,
and silt content.  Table C provides the estimates of hydraulic
conductivity.

-------
                                                                          3-24
                                  TABLE C
      HYDRAULIC CONDUCTIVITIES ESTIMATED PROM GRAIN-SIZE DESCRIPTIONS
                             (In Feet Per Day)
Grain-Size Class or Range
Prom Sample Description
I Degree of Sorting
f Poor
| Moderate
Well
Silt Content
Slight |
Moderate
High
Pine-Grained Materials
Clay
Silt, clayey
Silt, slightly sandy
Silt, moderately sandy
Silt, very sandy
Sandy silt
Silty sand
1. 1
Sands and Gravels

Very fine sand
Very fine to fine sand
Very fine to medium sand
Very fine to coarse sand
Very fine to very coarse sand
Very fine sand to fine gravel
Very fine sand to medium gravel
Very fine sand to coarse gravel
Fine sand
Fine to medium sand
Fine to coarse sand
Fine to very coarse sand
Fine sand to fine gravel
Fine sand to medium gravel
Fine sand to coarse gravel
Medium sand
Medium to coarse sand
Medium to very coarse sand
Medium sand to fine gravel
Medium sand to medium gravel
Medium sand to coarse gravel
Coarse sand
Coarse to very coarse sand
Coarse sand to fine gravel
Coarse sand to medium gravel
Coarse sand to coarse gravel
Very coarse sand
Very' coarse sand to fine gravel
Very coarse sand to medium gravel
Very coarse sand to coarse gravel
Pine gravel
Fine to medium gravel
Pine to coarse gravel
Medium gravel
Medium to coarse gravel
Coarse gravel










13
27
36
48
59
76
99
128
27
53
57
70
88
114
145
67
74
84
103
131
164
80
94
116
147
184
107
134
1270
207
160
201
245
241
294
334
I
I
Les








20
27
41-47
-
-
-
-
-
40
67
65-72
-
-
-
-
80
94
98-111
-
-
-
107
134
136-156
-
-
147
214
199-227
-
214
334
289-334
231
468
468

s than
1 - 4
5
7-8
9 - 1
11
13


27
-
-
-
-
-
-
-
53

-
-
-
-
-
94
-
-
-
-
-
134
-
-
-
-
187
-
-
-
267
-
-
401
-
602

.001



1




23
24
32
40
51
67
80
107
33
48
53
60
74
94
107
64
72
71
84
114
134
94
94
107
114
134
114
120
147
160
227
201
234
241
294
334










19
20
27 -
31
40
52
66
86
27
39
43
47
59
75
87
51
57
61
68
82
108
74
75
88
94
100
94
104
123
132
140
167
189
201
243
284










13
13
21
24
29
38
49
64
20
30
32
35
44
57
72
40
42
49
52
66
82
53
57
68
74
92
74
87
99
104
107
134
144
160
191
234
)Reduce by 10 percent if grains are subangular

-------
                                                            3-25

3.7    CONSOLIDATION TESTS
As originally defined by Terzagi  (Terzaghi  and  Peck,  1967)  the
coefficient of consolidation  (Cv) of a saturated,  compressible,
porous medium is related to the hydraulic conductivity  by:
                                                            (16)
           -v    pga

where
           K is the hydraulic conductivity, LT~1,
           p is the fluid density, ML~3,
           g is the gravitational constant, LT~2,  and
           a is the soil's compressibility, LM~lT2.

The compressibility can be determined  in  the  laboratory  with
several types of consolidometers, and  is  a function of the
applied stress and the previous  loading history.   Lambe  (1951)
describes the testing procedure.

The transfer value of results from this testing procedure is
influenced by the extent to which the  laboratory loading simu-
lates field conditions and by the consolidation rate.  The
laboratory loadings will probably be less than the stress that
remolded clay liner will experience; therefore, the use  of  an
already remolded sample in the consolidometer will probably
produce no measurable results.   This suggests that the test is
of little utility in determining the hydraulic conductivity of
remolded or compacted, fine-grained soils.  Second, the  con-
solidation rate determines the length  of  the  testing period.

-------
                                                           3-26





For granular soils, this rate is fairly rapid.  For fine-grained



soils, the rate may be sufficiently slow, so that the pre-



viously described methods will provide faster results.



Cohesive soils (clays) must be trimmed from undisturbed samples



to fit the mold, while cohesionless sands can be tested using



disturbed, repacked samples (Freeze and Cherry, 1979).





In general, EPA believes that consolidation tests can provide



useful information for some situations, but prefers the pre-



viously described methods because they are direct measurements



of hydraulic conductivity.  Hydraulic conductivity values



determined using consolidation tests are not to be used in per-



mit applications.







3.8   FRACTURED MEDIA



Determining the hydraulic properties of fractured media is



always a difficult process.  Unlike porous media, Darcy's Law



is not strictly applicable to flow through fractures, although



it often can be applied empirically to large bodies of frac-



tured rock that incorporate many fractures.  Describing local



flow conditions in fractured rock often poses considerable dif-



ficulty.  Sowers (1981) discusses determinations of hydraulic



conductivity in rock.  This reference should be consulted for



guidance in analyzing flow through fractured media.





Fine-grained sediments, such as glacial tills, are commonly



fractured in both saturated and unsaturated settings.  These



fractures may be sufficiently interconnected to have a significant

-------
                                                           3-27





influence on ground-water flow, or they may be of very limited



connection and be of little practical significance.





Frequently, a laboratory test of a small sample of clay will



determine hydraulic conductivity to be on the order of



10~8 cm/sec.  A piezometer test of the same geologic unit over



an interval containing fractures may determine a hydraulic con-



ductivity on the order of perhaps 10~5 or 10~6 cm/sec.  To



assess the extent of fracture interconnection, and hence the



overall hydraulic conductivity of the unit, several procedures



can be used.  Closely spaced piezometers can be installed; one



can be used as an observation well while water is added to or



withdrawn from the other.  Alternately, a tracer might be added



to one piezometer, and the second could be monitored.   These,



and other techniques are discussed by Sowers (1981).





For situations that may involve flow through fractured media,



it is important to note in permit applications that an apparent



hydraulic conductivity determined by tests on wells that inter-



sect a small number of fractures may be several orders others



of magnitude lower or higher than the value required to



describe flow through parts of the ground-water system that



involve different fractures and different stress conditions



from those used during the test.

-------
                                                            4-1





                         4.0  CONCLUSION







By following laboratory and field methods discussed or



referenced in this report, the user should be able to determine



the fluid conductivity of materials used for liners, caps,



and drains at waste-disposal facilities, as well as materials



composing the local ground-water flow system.  If fluid-



conductivity tests are conducted and interpreted properly,  the



results obtained should provide the level of information



necessary to satisfy applicable requirements under Part 264.

-------
                                                            5-1


                       5.0  REFERENCES
Acker, W. L. , III, Basic procedures  for  soil  sampling  and  core
     drilling, Acker Drill Co.,  246  p.,  1974.

Allison, L.  E., Soil Science, vol. 63, pp.  439-450,  1947.

American Society for Testing and Materials  (ASTM), Annual  Book
     of ASTM Standards, part 19, 1978.

Anderson, D., and K. W. Brown, Organic leachate  effects  on the
     permeability of clay liners, in Proceedings of  Solid  Waste
     Symposium, U.S. EPA, p. 119-130, 1981.

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. 233-238,  1980.

Conway, R. A., and B.  C. Malloy  (eds.),  Hazardous Solid  Waste
     Testing:  first conference, ASTM Special Technical
     Publication 760,  1981.

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.

Fireman, M., Soil Science, vol.  58,  pp.  337-355, 1944.

Freeze, R. A., and J. A. Cherry, Groundwater, Prentice Hall,
     604 p., 1979.

Gordon, B. B., and M. Forrest, Permeability of soil  using  con-
     taminated permeant, jLn Permeability and Groundwater
     Contaminant Transport, ed.  T. F. Zimmie and C.  0. Riggs,
     ASTM Special Technical Publication  746, p.  101-120, 1981.

Hillel, D.,  Soil and Water, Academic Press, 288  p.,  1971.

Hvorslev,  M. J., Time lag and soil permeability  in groundwater
     observations, U.S. Army Corps of Engineers  Waterways
     Experiment Station Bull. 36, 1951.

-------
                                                            5-2


Johnson, A. I., Symposium on soil permeability, ASTM STP 163,
     American Society of Testing and Materials, Philadelphia,
     pp. 98-114, 1954.

Johnson, E. E., Inc., Groundwater and wells, Johnson Division,
     UOP, 440 p., 1975.

Lappala, E. G., Quantitative hydrogeology of the Upper
     Republican Natural Resources District, Southwest Nebraska,
     U.S. Geological Survey Water Resources Investigations 78-38.

Lambe, T. W., Soil testing for engineers, John Wiley, N.Y.,
     1951.

Lohman, S. W. , Groundwater hydraulics, U.S. Geological Survey
     Professional Paper 708, 70 p., 1972.

Lohman, S. W., and others, Definitions of selected ground
     water terms - revisions and conceptual refinements,
     U.S. Geological Survey Water Supply Paper 1988, 1972.

Manufacturing Chemists Association, Guide for safety in the
     chemical laboratory, Van Nostrand, Reinhold Co., N.Y.,
     1971.

Mitchell, A. K., and J. S. Younger, Permeability and capillarity
     of soils, ASTM STP 417, American Society for Testing and
     Materials, Philadelphia,, pp. 106-139, 1967.

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

Olsen, R. E., and D. E. Daniel, Measurement of the hydraulic
     conductivity of fine-grained soils, in Permeability and
     Groundwater Transport, ed. T. F. ZimmTe and C. 0. Riggs,
     ASTM Special Publication 746, p. 18-64, 1981.

Papadopulos, S. S., J. D. Bredehoeft, and H. H. Cooper, Jr., On
     the analysis of "slug test1 data, Water Resources Research,
     9, p. 1087-1089, 1973.

Schwartzendruber, D., Soil Science Society of America Proceed-
     ings, vol. 32, no. 1, pp. 11-18, 1968.

Sowers, G. P., Rock permeability or hydraulic conductivity - an
     overview, in Permeability and Groundwater Transport, ed.
     T. P. ZimroTe and Co. 0. 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.

-------
                                                              5-3
Terzaghi, K.. ,  and R. B. Peck, Soil riechani.es in Engineering
     Practice, 2nd Ed., John Wiley & Sons, N.Y., 729 p., 1967.

Walton, W. C. , Groundwater resource evaluation, McGraw Hill,
     664 p., 1970.

Wilkinson, W.  B., In situ investigation in soils and rocks,
     British and Geotechnical Society, Institution of Civil
     Engineers, London, pp.  311-313, 1969.

U.S. Army Corps of Engineers, Laboratory Soil Testing, Water-
     ways Experiment Station Publication EMlllO-2-1906, 1970.

U.S. Environmental Protection Agency, Lining of waste impound-
     ment and disposal facilities, Office of Solid Waste Report
     SW-870, 1980.

U.S. Environmental Protection Agency, Hazardous waste guide-
     lines  and regulations (proposed), Federal Register,
     Part IV,  Dec. 18, 1978.

U.S. Environmental Protection Agency, Test Methods for Evaluating
     Solid Waste, 2nd Edition, SW-846, Superintendent of Documents,
     Government Printing Office, Washington, D.C., 1982.

-------
                                                    6-1
              6.0 Appendix A

   Values of the function F(a,B) for use in
the conventional and pressurized slug tests.
      Source: Papadopulos et.al. (1973)
7Vr«»
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
0.9989
0.9980
0.9972
0.9984
0.9956
0.9919
0.9848
0.9782
0.9718
0.9655
0.9361
0.8828
0.8345
0.7901
0.7489
0.5800
0.4554
0.3613
0.2893
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
a - 10-'
0.9996
0.9992
0.9985
0.9978
0.9971
0.9965
0.9934
0.9875
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
0.008898
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
0.8383
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
0.9866
0.9824
0.9784
0.&587
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
o - 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
0.003863
0.002938
0.001348

-------
            6.0 Appendix A  (continued)
 Extended values of F(a,6) for use  in  slug tests.
     Source:  Bredehoeft and Papadopulos (1980)
                                                      6-2
as 0.1
acO.2
a«0.5
a»2
                                     a* 5
                  a* 10
C.OOC001
e.oocoo?
o.ontoo*
O.OOC006
O.OOC008
O.QBCO)
o.ooco?
O.AOCO*
o.ooco*
O.OPCOB
o.ooci
fl.Ont?
O.OOC*
o.ooc*
o.oncs
O.OPl
0.102
0.00*
o.ont
O.onf
0.01
O.OJ
0.04
o.oe
t .OP
0.1
e.2
0.4
O.f
0.8
u
2.
*•
e.
e.
10.
20.
40.
*0.
HC.
inc.
?no.
*nfl.
60C.
SAO.
1000.
0.9993
0.9990
0.94B6
0.99«2
1.99«0
0.9977
0.9966
3.9955
0.99*4
0.9936
0.9924
0.989H
0.9««55
0.9*22
1.9794
n.9769
0.9670
O.V52H
0.9417
0.93?2
0.9238
0.8904
1.8*?1
0.8t)4«>
n.773*
0.7459
0.641P
0.5095
0.4J27
0..159P
0.3117
0.17ftf
O.OP761
0.0?5?7
0.039*3
0.03065
0.01*0*
0,0<16680
0.00*167
0.003?*2
O.OC2577
0.001271
e.noo*307
0.0004141
P. 00031*0
0.0002510
0.99«0
0.99Cfi
0.99tO
0.947S
0.9971
0.99C6
0.99S5
0.993A
0.99Z2
0.9909
0.9»59
0.96S7
0.97S7
0.9752
O.S713
0.9«79
0.9S46
0.93S7
0.9211
0.9089
0.89*2
0.8S<2
0.7980
0.75*6
0.71SO
0.6865
C.577*
0.445*
0.36*?
0.307?
0.2%* e
0.1519
0.67*96
G.04f9C
0.03tS6
0.02670
O.OI3fl
o.nntsts
0.00*310
0.003214
0.00?5*9
o.oni?6'<
0.0006295
O.OOC41H«
C. 0003137
0.0002506
0.9964
0.9977
0.9968
0.9961
0.9955
0.9949
fl.<»92?
0.9^99
0.9877
0.98SA
0.9b<»l
0.977f
0.9685
0.9615
0.95S7
«.9505
0.9307
0.9031
0.8025
0.8654
0.8SQB
0.7947
0.7214
0.6697
A. 6289
O.SVS1
0.4799
0.3566
0.2«64
0.2397
0.206)
0.1202
0.06*20
0.0*331
0.0325*
fl.026no
0.012afl
0.006774
0.00*229
0.003163
0.002S2f>
O.OOl?5A
0.000*372
0.0004177
0.0003131
0.000250*
0.9977
0.9968
0.9955
0.9945
0.9936
0.9929
0.9900
0.9858
0.9827
0.9ROO
0.9777
0.9687
0.9560
0.9*65
0."3«5
0.9315
0.904A
0.66R6
O.«419
0.4202
C.8017
0.7336
0.6*89
0.5919
0.54H6
0.5137
0.4010
0.7902
0.2311
0.1931
0.1663
0.09912
0.05521
0.03830
0.02933
0.02376
0.01219
O.OOM71
0.00413?
0.00310*
0.00?*87
0.001247
0.00062*2
0.000*1*3
0.00031?3
o«noo?4«s
0.9968
0.9955
A. 9936
0.99?2
0.9910
0.9900
0.9H58
n.9»oi
0.*757
0.9720
0.9<,86
0.'S62
0.9389
O.V?5«
0.9151
fl.9057
0.0702
o.e?32
0.7896
0.7626
O.?*00
0.6595
0.5*5*
0.5055
0.4618
0.*276
0.3J3*
0.2?9Z
0.1P17
0.1521
0.1315
O.OaO**
0.0*660
0.0?32»i
0.0?S9«
0.02l3n
0.0]133
0.005*97
0.003994
0.0030??
0.002*^1
0.001230
O.OQ06195
0.000*1*1
0.00031 10
0.0002*90
0.9948
0.9927
0.9698
0.9876
0.9857
0.98*1
0.9776
0.9687
0.9619
0.9562
0.9512
0.9321
0.9061
0.0869
0.8711
0.8576
0.8075
0.7*39
0.7001
0.6662
0.638*
0.5*50
0.**S*
0.3872
0.3*69
0.3168
0.2313
0.1612
0.1280
0.1077
0.09375
0.05940
0.03621
0.02663
0.0212S
0.0177*
0.0099*3
0.005395
0.&03726
0.002853
0.002313
0.0(1119*
0.0006085
0.000*087
0.0003078
0.0002*69
0.9923
0.9894
0.9853
0.9822
0.9796
0.9773
0.9683
0.9SS8
0.9*6*
0.9387
0.9318
0.9059
0.8711
0.8*58
0.8253
Or8079
0.7*50
0.668*
0.6178
0.5797
0.5*92 "
0.4517
0.3556
0.3030
0.2682
0.2*28
0.17*0
0.1207
0.09616
0.0813*
0.07120
0.0*620
0.02908
0.02185
0.01771
0.01*99
0.008716
0.00*898
0.003«*5
0.002668
0.002181
0.0011*9
0.00059**
0.000*016
0.0003035
0.00024*0

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        APPENDIX B
IMMERSION TEST  OF MEMBRAWE




   LINER MATERIALS FOR




COMPATIBILITY WITH WASTES

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                             DRAFT


                          Method  9082


          '  IMMERSION TEST OF MEMBRANE  LINER MATERIALS
                  FOR COMPATIBILITY  WITH  WASTES



1.0  Scope and Application


     1.1  This'test  method  is  for use  in determining  the  effects


          upon the physical properties  of flexible  ner.brane liner


          materials  intended  to  contain  chemicals   in  a  pit,


          pond, lagoon  or  landfill-type  installation,   of  the


          chemical environment  expected to  be encountered.   Data
                                                           s

          from these  tests  will  assist  in  deciding  whether  a


          given liner  material  is   acceptable  for  the  intended


          application.


     1..2' This method is based on material  resulting  from  wor>; by


          the National  Sanitation Foundation, Dr. Henry E.  Haxo,


          Dr. Robert Landrerh, ^acreccr.,  Inc. and Z?A:s  .;ur.^c«ral


          •Environmental Research  Laboratory  in   Cincinnati,   On.


2.0  Summary of Method


     2.1  In  order  to  estimate  long  term compatability,   the


          liner material  is  exposed  to  the expected  chemical


          environment for  a  period  of 120  days  at  an elevated


          temperature.  A  comparison of  the membrane's physical


          properties before  and  after  this contact period  is


          used to estimate  the properties  of  the  liner  at  the


          time of site closure.


3.0  Interferences


4.0  Apparatus and Materials


     4.1  Exposure tank - A size sufficient  to contain  the  sanoles

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          they do not touch bottom  or  sides  of the tank, or each



          other; for stirring  the  liquid  in  the  tank;  and  for



          holding the specimens  in  such a manner  that the liner



          material contacts the test solution only on the surface



          that would face  the  waste in an actual  disposal site.



          The tank shall be equipped with  a  means  of maintaining



          the solution at a temperature of 5CHh2°C and for prevent-



          ing evaporation  of the  solution (e.g.,  cover equipped



          with a reflux  condenser).  The Agency understands that



          one such device  is  manufactured  by  A.ssociat.ec Design



          and Manufacturing  Company,   814  North  Henry  Street,



          Alexandria, VA 22314,  (703)549-5999.



    4.2  Stress-strain machine  suitable for measuring elongation,



          tensile strength, tear and puncture resistance.



     4.3  Jig for testing puncture resistance.



     4.4  Labels and holders for specimens, of materials known to be



          resistant to the specific wastes.   Holders of stainless



          steel, and tags  made  of 50 mil  polypropylene, embossed



          with machinist's numbering dies and  fastened with stain-
                                  *


          less steel wire,  are  resistant to most wastes.



5.0  Reagents



6.0  Sample Collection Preservation and Handling



     6.1  For  information  on  what  constitutes a  representative



          sample of  the waste  fluid  to  employ,   refer  to  the



          appropriate guidance  document listed below:



          1. RCRA Guidance Document: Surface  Impoundments, Liner

             Systems, Final Cover,  and Freeboard  Control. Issued

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             July 1982 and  used  with 40 CFR  254. 221 (a)  and (c),
             and 264. 228 (a) .

          2. RCRA  Guidance  Document:  Waste  Pile  Design,  Liner
             Systems. Issued  July  1982  and  used  with  40  CFR
             264.251(a),  264.252, and 264.253.

          3. RCRA Guidance Document: Landfill Design, Liner Systems
             and Final Cover.  Issued Julv  1982  and used with 40
             CFR 264.301(a)  and 264.310(a)~.
7 . 0 Procedure
     7.1  Obtain  a  representative  sample  of.  the waste  fluid.

     7.2  Perform the ^following tests on unexposed samples of the

          polymeric  membrane liner material:

          7.2.2  Puncture resistance, three specimens

          7.2.3  Tensile strength in two directions,  three speci-

                 mens in each direction

          7.2.4  Elongation at  Break,  (This  test  is only  to be

                 performed on  membrane material  which  does  not

                 have a  fabric  or other  non-elasrcmeric  support

                 on  its 'reverse [away from waste] i'uce.)

          Tests are  to  be  performed  according  to the  protocols

          referenced in Table  9082-1.   See  Figure 9082-1  for  a
                                  *
          suggested  cutting pattern.

     7.3  Cut pieces of the lining material, "of a size  to  fit sample

          holder,  and of  a  sufficient number to permit at  least

          three samples  for  each  test   at  each   test  period.

     7.4  Label the  test  specimens with  a plastic  identification

          tag and  suspend in sample  of the waste .fluid.

     7.5  Expose the  sample to the  stirred  waste  fluid held at

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     7.6  At  the  end  of  30,  60,  90  and  120 days  of exposure,



          remove sufficient  specimen  from  the   waste fluid   to



          determine the membrane's physical properties  (see  7.2).



          Place wet  specimen  in  a labelled  container of  fresh



          waste fluid  at  room temperature for at' least one hour



          to effect cooling prior to testing.



     7.7  Tha sample  should  te tasted  within 24  hours of  removal



          from the bath.  Tc'test the immersed! sample,  wipe  off any



          waste fluid,  rinse with  deioriizsd  water,  blot specimen



          dry, and  measure  the physical  properties  listed   in



          7.2.



7.8  Results and Reporting



     7.8.1  Plot  the  curve "for   each property  over the  time



            period 0 to 120 days.



     7.8.2  Report all raw, tabulated,  and plotted  data. Evaluation



            of the  results  is described  "in the RCRA  guidance



            documents listed under 6.1.



8.0  Quality Control



     8.1  Determine the mechanical  properties of identical  non-



          immersed and"immersed specimens  in  accordance with the



          standard methods for  the specific physical property test.



          Conduct mechanical property  tests   on   nonimmersed  and



          immersed specimens prepared  from  the   same sample  or



          lot of material in the same manner and run under identical



          conditions.   Test immersed  specimens immediately after



          they are removed from the  room temperature test solution.

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               DATE DUE
 PVC(
  .etic  thermoplastic  polymer made
                                   Family of  polymers   produced  by
                                   on polyethylene.   The  resulting
                                   tin 25 to 45% chlorine by weight
                                    sed on isobuf/lene  and a small
                                    ites for vulcanization.

                                     e for a synthetic  rubber based
 CM (Crosslinr.ed chlorinated polyethylene):
     ethylene.
                                     A polymer  prepared by  the  low
                                     •ylene  as   the   sole  monomer.

                                     nsr):   A  synthetic  elastomer
                                     id a  small  amount of nonconju-
                                      vulcaniz~tion.

                                        Synthetic  rubber including
                                      ers  which  ar :•  saturated, high
                              	       ers  with  :hloromethyl side
                              ,»,*•*•»!»«•»•*• nopolymer (C" )  and a copolymer
                                     oxide(SCO).
             S3=  cniorir.atea
PE.-EP-A (Polyethylene ethylene/propylene-alloy!:   A blend of poly-
     ethylene  and "poly(ethylene/propylene).

HDPE-A  (High  density  polyethylene / rubber alloy):    A blend  of
     high density polyethylene and rubber.

CSPE (Chlorosulfonated polyethylene):   Family of  polymers that are
     produced  by polyethylene  reacting with   chlorine   and  sulfur
     dioxide and usually containing  25  to 43% chlorine  and 1.0  to
     1.4% sulfur.

TN-PVC (Thermoplastic nitrile-polyvinyl chloride):  An   alloy  of
     thermoplastic   unvulcanized  nitrile  rubber  and    polyvinyl
     chloride.

T-EPDM (Thermoplastic EPDM):  An ethylene-pro'-ylene diene monomer
     blend resulting in a thermoplastic elastoncr.

EIA  (Ethylene interpolymer alloy):    A blend ^-f  polyethylene  and
     polyvinyl  chloride  resulting   in  a thermoplastic  elastomer.

.PVC-CPE  (Polyyinvl  chloride - Chlorosulfonated v-lvethvlene  allov):
 U L Env;rofimental Protection Agencv
 f^ygJon V, Library
 230 South Dearborn Street
6

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                           TABLE 9082-1




             PHYSICAL PROPERTY TESTING PROCEDURES




           [Appropriate ASTM or FTMS(*) Testing Method]
Polymer
FVC
CPE
Butyl rubber
CP
KDPE
E?DM
CO, ECO
CM
PE-EP-A
HDPE-A
CSPE


TN-PVC


T-EPDM
-

EIA


PVC-CPE
Tensile Strength
& Elongation at Break
D832
D882
D412
D.412
D63S
D412
D412
D412
D412
,
Do 38 Type IV Dunbeli
at 2 inches/second
,
D751 Method A


D751 Method A

•
•
D751 Method A


D751 Method A


D882 Method A
Tear
Resistance
D1C04 Dia C
D1004 Die C
C624 Die C
D624 Die C
-
D10C4 Die €
D624 Die C
D624 Die C
D624 Die C
D1004 Die C
DIOC4 Die C
D751 as
modified in
Appendix A
D751 as
modified in
Appendix A
D751 as
modified in
Appendix A
•
D751 as
modified in"
Appendix A
D1104 Die C
! Puncture
Resistance
"
1 *2065
*2065
.
.
*2065
•
*2065
'
*2065
*2065
*2C65
*2065
*2065
"2055
*206S


*2065


*2065


*2065


-*2065
Abbreviations:



ASTM:  American Society for Testina and Materials

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          •I***;
   TEAR RESISTANCE.
   TEST SPECIMENS

                                                 PUNCTURE RESISTANCE
                                                        SPECIMEN-"
                                                 ^ -^ "^1,
Figure 9082-1.   Suggested  pattern for  cutting test  specimens

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