Federal Register / Vol. 52. No. 74 / Friday, April 17, 1987 / Proposed Rules
4. Conclusions Based on New Data
The information collected and
included in the background document
argues strongly that the composite
bottom liner with the FML upper
component and compacted low-
permeability soil lower component will
significantly enhance the leachate
collection and removal efficiency and
the leakage detection capability of the
LOCKS. The composite liner best meets
the goals of preventing migration out of
the unit and detecting the leak at the
earlist practicable time. It is also more
effective in meeting the goal of the
liquids management strategy for
maximizing leachate collection and
removal.
Minimum Technology Guidance
The draft technical guidance
documents noticed today are second
drafts resulting from comments
submitted on the first drafts that were
sent to state agencies, environmental
groups, trade associations and the
regulated community. These second
drafts are significantly different from the
original drafts as a result of the
comments received EPA solicits
comments from the general public on
these revised drafts of technical
guidance for single and double-liner
systems.
The draft double liner guidance. EPA/
53O-SW-85-014. applies to new units
and lateral expansions and
replacements of existing units at
hazardous waste laT"}f"b and surface
impoundments. The two double liner
syserms discussed are those proposed in
the March 28,1980, preamble to th* (51
FR10707-10711) double liner and
leachate colleciton system rule. The
draft technical guidance ^TKT*HTW^
discusses each uner system with respect
to design, construction. inf^T^Tiii •*"*
operations.
The draft single Hmrjyfaftm^, EPA/
530-SW-85-013, is intended to provkk*
guidance on design in accordance_wjjfr
section 3015{a) of RGRA for interfe*
status waste piles and for certain
surface impoundments ***& ?nndf^?< (40
CFR Part 264.221 and 384301,
respectively]. The new requirements for
interim status waste piles apply to new
units, and replacements and lateral
expansions of existing units. Other
applicable hazardous waste
management units include new landfills
and surface impoundments and lateral
expansions or replacements of existing
landfills and surface impoundments that
have been permitted before November 8,
1984. In addition, the existing single liner
standards of 40 CFR 2B4~221(a) for
surface impoundments, and 40 CFR
264.301(a) for landfills, are still
applicable to portions of existing unite
that are not covered by waste et the
time of permit issuance. Therefore, the
draft single Uner guidance is intended to
provide guidance for land disposal
facility owners or operators and EPA
and State regulatory personnel on
designs that the Agency believes meet
the single liner performance standards
of 40 CFR 264.221(a), 264J51(a), and
264.301(a). This document identifies
design, construction, and operation
specifications that can be used by
owners or operators in order to comply
wth the requirements of those sections
of the EPA rules.
Dated: April 13,1917.
J.W.McGrmw,
Acting Assistant Administrator for Solid.
[FR Doc. 67-4678 Filed 4-16-67; 8:45 am]
DEPARTMENT OF COMMERCE
50 CFR Pert 652
National Oceanic end Atmospheric
Attentte Surf Ctom and Oeeen Oueheo
AODWVt National Marine Fisheries
Service (NMFS), NOAA, Commerce.
ACTION: Notice of availability of a
fishery management plan •iimiulnumt
and request tor comments. ,
BUMSMMV: NOAA issues this notice that
the Mid-Atlantic Fishery Management
Council has submitted Amendment 7 to
the Fishery Management Pian for the
Atlantic Surf d"Tn >r"^ Preen ffr
Fisheries (FMP) for review by. the
Secretary of Commerce. Comnsats are
invited from the public on the
amendment and associated documents.
DATE Comments will be accepted until
June 11,1987.
ADomtt; Send comments to Richard
Schaefer, Acting Regional Director.
Northeast Regional Office. Netionel
Marine Fisheries Service, 14 Elm Street.
Gloucester. MA 01930. Mark "Comments
on Atlantic surf clam and ocean quahog
plan" on the envelope.
Copies of the amendment and its
associated documents ere available
from John C. Bryson, Executive Director,
Mid-Atlantic Fishery Management
Council. Room 2115. Federal Building.
300 South New Street. Dover. DE19901-
6790.
MM RMTHtN INMMMATMN CONTACT!
Bruce Nichols (plan coordinator)! 617-
281-3600, ext 232.
sjumnsjNTAiiY neKMMATMN: The FMP
and this amendment were prepared
under the Magnuson Fishery
Conservation and Management Act
This amendment proposes measures
to (1) change the quarterly quotsv. *
each quarter, (2) remove for all areas the
5.000 bushel threshold for transfer of
unharvestad quote from one quarter to
the next, (3) add the provision that any
unharvested quota la the Nantacket
Shoals and Georges Bank areas be
distributed proportionally among the
remaining quarters of the year. (4)
remove the 10% limit on carryover of
unharvested quota from one year to the
next (8) require annual renewal of
vessel permits, and (•) change the
regulations to enhance prosecution and
enforcement.
Proposed regulations for this
a^yyfm^n^ ^ffl ffS published TTJ**1*1K
day*
(13 U.aC. 18010*40?.)
Data* Apa 14. tear.
Director. Offtct ofFlihtriM Management.
PR Doc 87-8721 FBed 4-1*47; ROB pa}
susie COM SMS»CMI
-------
12588
/ Vol 52. No. 74 / Friday. A|rt 17.
York's meathly vacaoavbned leak
check pracedwM did not satisfy the
statutory criterioBof beiagin
acoardaace-witb; good aagineeriag
practices «ad was not equivalent to the
quality control procedures specified in
5 85.2217. However; New York agreed
that these error rates wen undesirable
and has changed its procedures to
include weekly probe/port <
""^p-mton
leak checks, effective June 3,I985i This
change is consistent with the procedure
specified in § 85.2217(d].
D.
The quality control procedures in
§ 85.2217 of the warranty short test
regulations have been determined by the
Administrator to meet the statutory
criteria of being readily available, in
accordance with good engineering
practice*, and resulting in the short tests
being reasonably capable of being
correlated with the FTP (see 45 PR
34802). fa me case of New York's
alternative qtwfiry control procedures,
since Aey_aro camntiy being used, ft is
clear that these procedures meet the
first criterion of being readily available.
After revisions to New York's quality
control procednres to indnde probe/port
comparison leak checks and analyzer
calibration ges checks through the
sampling probe. New York's alternative
quality control pioceihaes differ rrom
5 85.2217 procedures ia two ways. The
gas calibration check is dene neetWy,
not weekly, aad the State uses high-
scak rather them low-scale calibration
gases. Cosapeneafeng far ftese
difference* is tke fact taetaH of Tna»m (whjek fcadaates
probe/pott rmaijiariaoBi leak checks).
result ine Ufbdearw of ovenUeyeteat
realiability and accttcacy. Tkenfere. it is
EPA's preliminary detemhution that
these procedures meet the criterion of
being in accordance with goad
eagteeedngpnctiom.
Based -oei theevahHtkiBidiecassed
above, tsda notice enmnaues 9A's
prelindnary detennteafioa Art A«
altematiTe in i npiiilau
guidance dnmaannls,
BATE CO&ODBODlinQBl fX5 SQlBIlitted OB
or before JonaXtMT
and
Regulatory Plexieaity Art, W&S.C. «8t
eteby verity
a~B9J«f X UDIlt—^ ••"-^••j ••••* «««aev aaan
wiU net have a-sigBfifeent advene
impectea a suTariaMlai aimubdt vt*M&
entities. TBeeriyeBefiespotemieny
affected bye fmeldetenmnatitmof
equivetency are mrtoraobile
manufactureni
two eefsae«keaid,e
by regulatory docketfefer
code f-
through Frii
warranty tafaffity may be effected.
rfowever, tnese nxanofacnifen ere
small entities. Tins, BDregohrtory
flerftrffity analyeis is rsqmred and
has been-pieeaied.
VrHrinjii ThnpAli aiaal laatu aa
"TT"'"" i ill Is mfn ii aai t si a»>ai iaai
and -hniilil naHiMta TaaailaljMq ITO
9327 Jar eBpaaBteeats^ tte «Hte mm
Imports, Labeling, Motor vehicle
pollution. Reportinj andncond keeping
requirements. Research Wamntiea.
Auuwri^r: Section 2t7.aeiM.Osa Air
Act as amended (42 U.&C. 7541 «nd 78IB(a)).
caejreiae
ofmaterieiJareair
docket Adi*
page.
A
followicg
,^
Skahn. in the Office of «oW Weete, VS.
Environmental Protsctiaa Ageecy «t tin
-------
Federal Register / Vol. 32. No. 74 / Friday. April 17, M67 / Proposed RaJos
address and telephone number listed
below:
Draft Minimum Technology Guidance
on Single Liner Systems for Landfills,
Surface Impoundments, and Waste
Piles— Design. Construction, and
Operation (EPA/530-SW-45-013);
Draft Minimum Technology Guidance
on Double Liner Systems for Landfills
and Surface Impoundments— Design,
Construction, and Operation (EPA/
530-SW-85-014);and
Background Document on Bottom liner
Performance in Double-Lined
Landfills and Surface Impoundments
(EPA/530-SW-87-013).
In addition, copies of the background
document an available far review in the
Office of Solid Waste (OS W) docket
room.
FOH njRTHOI MFOftMATMN CONTACT:
For general information, call the RCRA
Hotline, at (800) 424-8846 (tofl free) or
(202) 382-3800. For technical
information, contact Kraneta Skahn.
Office of Solid Waste (WH-666E) , U..S.
Environmental Protection Agency, 401 M
Sreeet SW, Washington, DC 204m (202)
382-4654.
issue regulations or technical gaids
Background
The Hazardous and Solid Waste
Amendments (HSWA) of 1964, require
that certain landfills and surface
impoundments must have two or more
liners aad a leachate collection system.
Specifically, section 3004(oXl)(A) of
RCRA, as amended by HSWA. requires
new tatnifiUff or surface impoundments,
each new landfill or surface
impoundment unit at existing i
and each lateral expansion or
replacement of a landfill or ear—_
impoundment unit at existing nciMtte*
(for which a perratt is received after
November 6,1964) to have at wast two
liners and a kechate collection system
above (for iaadfi&a) ae*)' "
liners (Le, dc«ble-lmari_.
technology rsqnreaaMts). I
liner and leachat*
requirements of 3084(e)ClXA) to new
units, replacement wiiwand lateral
expansion of existing ant* at interim
and surface
impoundments that are whhfa the waste
management ana identified in the permit
application with reepect to waste*
received *»&**i-s May 8. 1886.
Therefore, Tftti'ti lamMHla or surface
impoundments meat meet the doatte-
liner minimum technological
requirements of section 3004(o){lXA).
unless they qualify for an exemption
under sections 3004(o), 30060). Under
section 3004(oX5)(A). EPA is required to
by November a, 1966, implementing the
requirements of section aw(o)(l)f A).
In addition, section iDlS(a) of RCRA
requires new units, replacements and
lateral expansions of interim status
waste piles to comply with the single
liner and leachate collection and
removal system requirements with
respect to waste received beginning
May 8, 1985. Hie requirements for waste
pile units to 40 CFR 284.2Sl(a) and
265.254 and the draft technical guidance
for single liners cited above, provide
standards and guidelines for design,
construction, and operation of these
single-lined units.
Until EPA issues new regulations or
guidance on liners and laachate
collection systems in accordance with
section 3004(oX5), doable Iteer «y*teiM
may be designed, constructed, and
installed accordiag to the interim
statutory previsions of RCRA, section
3004(o)(5)(B), that wen codified on July
15.1985 (50 FR 28702). hi 40 CFR
264.221(c). 264.301(c). 285.221{a). and
265.301(a). These interim standard*
require that the top and bottom liners be
designed, operated, and contracted of
materials to prevent hazardous
constituent migration during the active
life and postctoaun can period for the
unit In the preamble to the July 15, W86,
regulation (56 FR 28702), me Agency
states that the top liner standard can be
met by a flexible membrane Uner (FML).
According to RCRA section
3004(oK5HB). the bottom Hner must be
constructed of at least three feet of
recompacted soil or other natural
materials with a lermeabilty of no
more than 1 x MT* cm/sec.
ta addition to double Uner and
under section SOMfeJH) of RCRA, a*
amended by HSWA. cafl for the
utilization of an approved leak detection
system (LDS) far new laadfflh. surface
impoundments, waste pfletv
veMfta^M^Mt^Mk^l eWvftiw j • • i • • • a • -
units. This IDS must be able to detect
leakage of hazardoas coaatitaent* at the
earliest practicable tarn. Section
3004(o)(4XA) require* EPA to
promulgate standards for the LDS no
later than May 6, 1067.
On March tt. 1966. EPA pripmJ
amendments to the interim statutory
provisions for double Unen under the
authority of section 3004fo)(S)(A). This
proposal sat forth alternative
performance steaxierds for double Haer
system* (51 FR 10*67-10711).
Under the first alternative, the
proposal requires a liner system to
include both top and bottom Unen
designed, operated, and constructed of
materials to prevent baordoo*
oonetituent migration daring the active
lite and post-does** can period (40 CFR
Part 284.221{c}). To meet this standard,
the top liner must be an FML (51 FR
1O70B). The proposal provides that the
bottom Hner performance standejd may
be met by a finer contnetoi of at least
a 3 foot layer of compacted sofl or other
natural material* with a i
hydreaec conductivity of no new than 1
x 10-' cm/sec (40 CFR 26*£21{e)).
Under the second alternative
proposed OK March 28,1966, the Hner
system must include a top Hner meeting
the same performance standard that is
described for the first alternative. The
bottom liner must consist of two
components that an intended to
function as one liner. The upper
component of the composite Hner must
be designed, operated, and constructed
of material* to prevent hazardous
constituent migration into the upper
component occurs before the end of the
post-closure can period. The lower
compoaent must be constructed of
compacted soil material with a
hydraulic conductiviry of no more than 1
x 10~* cm/sec. In the preamble, we note
that the composite liner should consist
of a PM^i
n) thick
(51 FR 10710).
Baaed on date available at the time of
the pnmoul EPA believed that both
the** system* could met the overall
double linac system goal of pievsntlm
hniardoos masrlhtettf mteraMea oatof
the unit dMiag the active li«* and poat-
closon cart laariodfiir dw tadlty.
However. kLthepmambU&PA
expressed some concern about the ion*>
tarmBerfQcmanceof Aeomuoar4 -i*wi
bottoai liaer (Si FR 10700), nottof Oua if
leachate HiioTatsa tawpjaa breaohki
,
trapped ia dw compacted lew
peaMabtiito *eJi «a«r casket than be
collected aad removed ia the Isachate
collection system between the Hint*.
EPA witt soon be propossnf
regulations for an approved leak
detection system (LDS) at newly
constructed units to meet the statutory
provision* in section SOMtofcHfA).
EPA's current position is that the
leachate collection aad removal system
(LCRS) proposed on March 26, 1986
-------
12568
Federal Renter / Vol 52t No. 74 / Friday. Anril 17. ion. /
!•
r
'i,
(with some technical modifications) will
serve a* the LDS for newly constructed
nn M a?d turfaca tapoundment units.
On March 28,1986. the Agency proposed
o require the LCRS between Uie liners
to be designed, constructed, maintained,
and operated to detect, collect and
remove liquids that leak through any
area of the top liner during the active
me and post-closure care period f40 CFR
Part 284.221(0)}. EPA plans to propose
LDS regulations in the near future.
These regulations will modify the
proposed LCRS by proposing additional
specific design standards requiring a
minimum bottom slope, a minimum
drainage layer hydraulic conductivity
and transmissivity, and a sump of
appropriate size to collect and remove
liquids efficiently. Additionally, under
the imminent LDS proposal the leachate
detection, collection, and removal
system (LDCRS) between the liners must
meet specified performance standards
for leak detection. It must be able to
detect a specified leakage within a
certain time period and to collect and
remove the liquids rapidly to minimize
the hydraulic head on the bottom liner.
In the course of developing these
proposed regulations we have collected
new data. As discussed more fully
below, this data indicates that
compacted soil bottom liners will not
detect and collect leaks as efficiently as
composite bottom liners.
EPA continues to believe that liners
are best used to facilitate the collection
and removal of leachate. This view of
liners is consistent with one of the
fundamental elements of the liquids
management strategy—to maximize the
collection and removal of leachate from
landfills, surface impoundments, and
waste piles. The overall objective of
pA's liquids management strategy is
for hazardous waste management unit*
to be designed both to minimi™ th.
amount of leachate generated and to
maximize the amount of leachate
collected and removed from the unit As
landfills and surface impoundment*
cannot currently be designed, •
constructed, or operated to completely
prevent leachate generation, emphasis
must be placed on "*»«frrrfring the
collection and removal of the leachate
from the unit Therefore; the extent to
which the proposed botton liner systems
enhance or detract from the leachate
detection, collection, and removal
capabilities of the LDCRS was studied
by EPA.
New Data
The Agency is reviewing data that are
currently available from modeling
efforts, actual performance and
technical engineering analyses that
compare the performance of these two
bottom liners with respect to the
following parameters:
• Leachate collection efficiency;
• Leak detection capability; and
• Leakage, both into and out of, the
bottom liner.
EPA believes that any one of these
factors will significantly influence the
performance of the bottom liner and,
therefore, may influence EPA's final
decision concerning the composition of
the bottom liner.
Today, EPA is making this
information available for public
comment The data are presented and
discussed in detail in a background
document for this notice and will be
considered along with other relevant
information provided by the public in
the development of the final double liner
rule. The background document is
entitled, "Background Document on
Bottom Liner Performance in Double-
Lined Landfills and Surface
Impoundments."
1. Background
Compacted soil liners have long been
used as barriers and foundations in
traditional civil engineering structures.
such as dams, canals, and highways.
They, therefore, have a long record of
strength and durability that allows them
to be used in these ways. However, as
porous and disaggregated materials,
soils an not impervious. In the case of
double-lined waste management units,
gravitational and capillary forces
present in an unsaturated. low
permeability soil liner will allow some
leakage through the top liner to be
absorbed into the bottom liner before it
can be detected, collected, and removed
by the LDCRS between the liners. Once
trapped in the liner, the hazardous
waste leachate will most likely migrate
through the liner and into the ^^
environment
Filed compacted, low permeability
soils are subject to nonuniform
hydraulic properties across and through
the linter, even with extensive
compactive and mixing effort and
moisture monitoring. Accordingly, a
compacted soil liner may contain
defects that increase the local effective
hydraulic conductivity and, hence,
detrimentally affect the liner's
performance.
In a compacted soil liner the thickness
conductivity of the liner system.
Therefore, while thicker liners may be
able to satisfy the "prevent migration"
clause through the post-closure care
period, they will not perform as
effectively as a more impervious liner
system, such as a FML, with respect to
the three factors cited above.
The use of a flexible membrane as a
liner significantly improves the leachate
collection efficiency and leak detection
sensitivity of the system. FML's consist
of interlocking synthetic polymers and
thus are significantly more watertight
than granular materials, such as soils.
There is still an element of vapor
diffusion, or permeation, that allows
liquid to migrate though a perfectly
intact FML. Nevertheless, the amount of
fluid migration through the liner is
extremely small and is estimated to be
comparable to that produced by a
porous materials with a hydraulic
conductivity in the range of 1 x 10~ u
cm/sec. This factor alone implies a far
greater performance capability of FML's
with respect to leachate collection
efficiency, as well as leak detection
sensitivity.
However, even with good construction
quality assurance, a FML may contain
defects that increase the local effective
hydraulic conductivity and, hence, have
a detrimental affect on the liner's
performance. Even under a good
construction quality assurance i
•u a-bvuiptuiuia sou uner ine minn^
will affect the time that liquids will
break through the bottom of the Uner
and enter the surrounding environment;
but it will not affect leachate collection
and removal efficiency, leak detection
sensitivity, and total leakage out of the
unit. These parameters are mainly
controlled by the effective hydraulic
per acre of Uner, based on i
analysis of the current technology.
On the other hand, a composite Uner
consisting of a FML upper component
and compacted low permeability soil
lower component has several
advantages and combines the strengths
and capabilities of both materials to
maximize leachate detection, collection.
and removal from the unit The FML
upper component greatly improves
leachate collection and removal
efficiency and leak detection sensitivity
of the LDCRS. In addition, the soil
component minimizes the migration of
liquids that leak through holes in i«
FML and provide some attenuation of
leakage. As discussed more specifically
below. EPA's analysis shows that the
composite bottom Uner system would
provide better leak detection sensitivity
and leachate collection and removal
efficiency than a compacted low
permeability soil It would also
significantly reduce the amount of
leakage into the bottom Uner and out of
the unit over time as a result of
increased leachate collection and
removal efficiency. Therefore, a well
constructed, installed, and operated
composite liner is expected to minimize
-------
Fedafti RagMUr / Vol 52, No. 74 / Friday. April 17. 1967 / Proposed Rules
hazardous constituent migration out of
the unit by maximizing leachate
collection and removal.
2. Engineering Analysis at Performance
Data
In order to analyze the performance
capabilities of the two bottom liner
systems, the Agency reviewed available
performance data for compacted soil
and flexible membrane liners from
actual landfills and surface
impoundments. (Actual performance
data on composite bottom lines does not
exist at this time.) The review of such
data indicates that as a general matter,
compacted soil liners do not have
uniform hydraulic properties across and
through the liner. FMLs, on the other
hand, possess mniform hydraulic
properties. The range of actual
performance data for compacted soil
and flexible membrane liners was used
in the Agency's modeling analysis to
provide an understanding of the leak
detection sensitivity and leachate
collection efficiency of the bottom liners.
(See section 3 below.) The background
document more fatty addresses the
performance capabilities of the two
bottom liner systems.
In addition, EPA recently conducted a
review of applications submitted for
RCRA hazardous waste facility permits
since November 8,1984, to determine
the type bottom liner selected for
installation at new landfills and surface
impoundments. Of some 183 units for
which permit applications were
submitted as of February 1987, only
sevau unite wan to be conriUKtad with
compacted low permeability soil bottom
liners. The vast majority of owners or
operators selected the composite bottom
liner rather than a compacted low-
permeauiiity soil liner. Many owners or
operators'have also indicated that they
plan to use a composite liner for the top
liner as well.
3. Analytical Data
Because only limited field data exist,
analytical and numerical modeling
approaches have been developed and
used by EPA to evaluate the
performance capabilities of the two
bottom liners at a typical landfill or
surface impoundment unit
Three modeling approaches were used
to evaluate leachate collection
efficiency, leak detection sensitivity.
and leakage into and out of the bottom
linen .
• steady-state, saturated, 1-
dimensional flow,
• transient unsaturated, 1-
dimensional flow; and
• transient unsaturated, 2-
dimensional flow.
These approaches reflect three .
different levels of analysis for
evaluating the performance of the
bottom liner. The results from each
analysis were compared and to tome
cases aggregated in order to determine
the representative values for leachate
collection efficiency, leak detection
sensitivity and migration into and out of
the bottom liner. A detailed dii
the background document Figures .
presented in this notice are derived from
the modeling efforts described in the
background document Today's notice
does not contain a complete discussion
of the applications of each approach to -
each performance parameter, such
discussion is, however, set forth in the
background document
The detection sensitivity is the
smallest leakage rate through the top
FML that can be detected hi the LDCRS
sump. For the compacted low
permeability soil liner at 1 x NT7 cm/
sec, the smallest leakage rate detected is
about 80-100 gallons per acre per day
(gpad) with a uniformly leaking FML top
liner, based on the 1-dimensional
saturated flow calculations (Figure 1).
The actual capability of a,compacted
soil liner is site-specific and will depend
on many factors (e.g., location of the
leak, effective hydraulic conductivity of
the liner, and the design of the LDCRS
between the liners). However, as a
general matter a bottom liner of
compacted soil with a hydraulic.
conductivity value of 1 x 10~* off/see
will perform significantly worsfcFor a
composite liner, the LDCRS can detect
leakage rates several orders ot >
magnitude smaller tins 80 gpidt i.en 1
gpad. Even with a few hole* in the FML
component the composite liner still
performs much better than compacted
soil liners with respect to leak detection
senstitivity.
of each modeling effort is presented in
-------
12570
Fede«i Regfcter./ Vol. 52. No. 74 / Fttdav. Anril 17.1987 / Proposed Rule.
LEAK DETECTION SENSITIVITY
r.ooo
600
Minimum Detectable
Leakage Rat*
Through Top Uner
(GalJAcre/Day)
Compacted Soil
K » IxNHcm/sec
400
200
TYPE OF BOTTOM UNER
Figure 1. Comparison of leak detection sensitivity for compacted soil and composite bottom liners.
KUMOCOOKI
-------
VoL 52. No. 74 / Friday. April 17. 1987 / Proposed Rulea
Federal Register /
The leachate collection efficiency is
the maximum possible leakage that can
be collected to the LDCRS sump divided
by the total leakage entering the LDCRS
through the liner. Figure 2 illustrates the
relative collection efficiencies of the
composite and compacted low
permeability soil liner systems assuming
uniform top liner leakage and steady-
state, 1-dimensional flow. Both systems
have greater than 90 percent collection
efficiency at very large leakage rates
(greater than 1000 gpad); at smaller
leakage rates that EPA believes are
more representative of current
technology and operating practices at efficiencies over 10 yean at « constant
dMmm^e
.,raet
"; " c°mPacte ow ««» be expected to EM observed to
an increase in hydraulic conductivity for £« W?omefn±mpactel
the compacted low permeability soil S h2m vK f W f°P
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12372
LEACHATE COLLECTION EFFICIENCY
Composite {intact)
100 r
LEACHATE
COLLECTION
EFFICIENCY
<*)
50 _
Composite with
Small FML holt
Compacted Soil
K • 1x10-7 cm/sac
Compacted Soil
K « 1 x 10* cm/sac
1 10 100 1,000 10,000
.TOP UNER LEAKAGE RATE (GaL/Acre/Day)
Figure 2. Comparison of laachata collaction afficiancias for compactad soil and composHa
bottom linars.
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*.-
Federal Register / Vol. 52. No. 74 / Friday. April 17. 1987 / Proposed Rules
12572
Leakage out of the unit refers to
leakage that passes into and through the
bottom liner. As illustrated in Figure 3.
composite liners have a much lower
potential to allow leachate to migrate
into the bottom liner. On a cumulative
basis over 10 years, leakage into the
bottom liner is higher for compacted
soils with a hydraulic conductivity of
1 x 10"' cm/sec, as opposed to
composite liners as shown in Figure 3.
Calculated results from the computer
simulations indicate that the composite
bottom liner performs conistently better
than compacted low permeability soils
with respect to maximizing leachate
detection, collection, and removal and
minimizing migration out of the unit
Based on these data, die difference in
performance is significant The other
important trend noted in evaluating the
data is that compacted low permeability
soil lines with effective hydraulic
conductivities greater than 1 x 10"*
cm/sec perform significantly worse.
KUmO COM «MO «0 M
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Paihaai HuJUn j Vol 52. «•, 74 j Prictey. April 17,1987 /
CUMULATIVE LEAKAGE INTO THE BOTTOM UNER
OVER TEN YEARS
200,000
150,000 —
CUMULATIVE
1EAKAGE INTO THE
BOTTOM UNER 100,000
(GalJAcrt)
Com pacttd Soil
K» 1x10-7 cm/sac
Composite
largataar(IOft)
50.000
TYPE OF BOTTOM UNER
Figure 3. Cumulativa laakaga into tha bottom linar ovar 10 yaars for a sida wall top linar laak at 50
galJacra/day.
BILLING COOC fMO-SO-C
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