### Characterization of Infi ltrati on Ra te Data to Support Grou ndw ater

M ode ling E fforts

Draft

Prepared for: U.S. Environmental Protection Agency Office of Solid Waste and Eme

rgenc y Re sponse CONTRACT NO. 68-W6-0061 Work Assignment No. 3-59

Pr ep ar ed by: Tetra Tech, I

nc. 3746 Mt. Diablo Blvd., Suite 300 Lafay ette, CA 94549

May 31, 2001i



### TABLE OF CONTE NTS

Page 1.0 Introduction 1
2.0 Literature Survey 2 2.1 Process 2 2.2 Results 2
3.0 Infiltration and Other Relevant Data 3 3.1 Geomembrane and Composite Liners 3 3.1.1 Review of Literature 5 3.1.2 Lea

k Detection Sy stem Flow Data 5 3.1.2.1 Analysis of Scop e of Data 6 3.1.2.2 Analysis of L

DS Flow Da

ta 8 3.1.3 Calculated Leakage Rates 10 3.1.4 Comparison of Actual and Calculated Le akage Rates 12 3.2 Geosynthetic Clay Liners 12 3.2.1 Review of Literature 12 3.2.2 Performance Da

ta 13 3.3 Compacted Clay L iners 13 3.3.1 Review of Literature 14 3.3.2 Infi ltration D ata 14 3.3.3 Hydraulic

Conductivity D ata 15 3.3.3.1 Analysis of Scop e of Data 15 3.3.3.2 Analysis of Hy

draulic Conductivity D ata 16
4.0 Summa ry and Rec omme ndations 17 4.1 Geomembrane and Composite Liners 17 4.2 Geosynthetic Clay Liners 18 4.3 Compacted Clay L iners 18 4.4 Recommen

dations 19
5.0 References 20
Appendix A Bibliography Appendix B Copies of Documents Containing Time-Varying Infiltration Data for

Geomembrane and Composite Linersii



### LIST OF FIGURES Figure 3.1-1. Distribution of LDS Flow Data by Geomembrane Material and Liner Type f or Geomembr

ane and Composite L

iners. Figure 3.1-2. Distribution of LDS Flow Data by Liner Ty pe and LDS Ty

pe for Geomembrane and Compos ite Li

ners. Figure 3.1-3. Distribution of LDS Flow Data by Type of Waste and Re gion for Geomembrane and Compos ite Li

ners. Figure 3.1-4. Distributi on of Waste Placeme nt Start Da

tes for G eomembr

ane and Composite Line rs. Figure 3.1-5. Distribution of LDS Flow Data by CQA Procedure and Line r Type for Geomembr

ane and Composite L

iners. Figure 3.1-6. Cumulative Distribution Functions of Average Monthly LDS Flows by

Liner Ty pe for Geomembrane and Comp osite Liners. Figure 3.1-7 Cumulative Distribution Functions of LDS Flow Measurement Period by Liner Typ e for Ge omembra

ne and Com

posite Liners. Figure 3.1-8. Cumulative Distributi on Funct

ion of L eak Den sities for

Geomembr

ane Liners. Figure 3.3-1. Number of Compacted Clay Liner Sites by

U.S. Region. Figure 3.3-2. Cumulative Distributi on Funct

ion of Fie ld Hy

draulic Conductivity Values for All Compacte d Clay

Line rs. Figure 3.3-3. Scatter Plot of Field Versus Labor atory Hy draulic Conductivity Values for Compacte d Clay

Line rs.iii



### LIST OF TABLES
Table 2.1-1. Lis t o f D at ab as es Us ed in Lit er at ur e S ur ve y. Table 3.1-1. Typ ical Def ects of G eomembr

ane Liners an

d Possible Ca

uses. Table 3.1-2. LDS F low Data base for Land fill Cells w

ith Geome

mbrane or Composite

Line rs. Table 3.1-3. Percent of Sites Reporting Parameters by Liner Ty pe for Geomembrane and Composite L

iners. Table 3.1-4. LDS Flow Database f or Landfills with Geomembrane or Composite Liners During the Post-Closure Period. Table 3.1-5. Statistics of Average Monthly LDS Flow Rates by

Liner Ty pe for Geomembrane and Compos ite Li

ners. Table 3.1-6. Statistics of Average Monthly LDS Flow Rates by

CQA Procedure for Geomembr

ane and Composite L

iners. Table 3.1-7. Statistics of LDS Flow Measurement Period by Liner Ty pe for Geomembrane and Composite L

iners. Table 3.1-8. Statistics of Average Monthly LDS Flow Rates During the Post-Closure Period for L andfills w

ith Geome

mbrane or Composite

Line rs. Table 3.1-9. Lea

k Density Data for Geomembr

ane Liners. Table 3.1-10. Leak Density Statistics by Potentially

Significant Parameter for Geomembra ne Liners. Table 3.1-11. Lea

k Density Data for Soil-Cover

ed Geome

mbrane L iners. Table 3.1-12. Ranges of Le ak Sizes found in Literature for Geome mbrane Liners. Table 3.1-13. Equations Representing Le akage Rates Through Hole s for Geomembrane and

Composite L

iners. Table 3.1-14. Calculated Leakage Rates (lphd) for Geomembrane and Composite L iners Assuming

Hole Size of

3.1 mm2

. Table 3.1-15. Calculated Leakage Rates (lphd) for Geomembrane and Composite L iners Assuming Hole Size of 1 cm 2

. Table 3.1-16. Calculated Leakage Rates (lphd) Through Holes in Geomembrane s Overlying

Geosy nthetic Cl ay

Line rs. Table 3.1-17. Comparison of Actual Versus Calculated L eakage Rates for Geome mbrane Line rs. Table 3.3-1. Infi ltration D ata for Compacte d Clay

Line rs. Table 3.3-2. Hydraulic

Conductivity D ata for

Compacte d Clay

Line rs. Table 3.3-3. Percent

of Sites Re

porting Paramet ers for Compacte d Clay

Line r Hy draulic Conductivities. Table 3.3-4. Statistics of Field Hydraulic Conductivity by Liner Material for Compacted Clay Line rs. Table 3.3-5. Statistics of Field Hydraulic Conductivity by Waste Manag ement Unit Type for Compacte d Clay

Line rs.iv



### ABBREVIATIONS
Abbreviation Definition ASH(M) Municipa l ash ASH(C) Coal ash CCL Compacted clay liner C&DW Construct ion and de

molition wa ste CSPE Chlorosulfonated polyethy lene CQA Construction quality assurance EPA U.S. Environmental Protection Agency FML Flexible membrane liner GCL Geosynthetic cla y liner GM Geomembrane GN Geonet GT Geotextile ha Hectare HDPE High density poly ethylene HW Hazardo us waste ISW Indu strial sol id waste IWEM Industrial Waste Manage ment Evaluation Model LCRS Leachate c ollection and removal system LDS Leak detection sy stem LL DPE Linear low density polyethy lene LMDPE Linear medium density polyethy lene lphd Lit ers p er he ctar

e per day (1 lph d = 9. 35 ga

llons/acr e/da y [ gpad] = 1.16 x 10 -10 cm/s) MSW Municipa l solid waste PS Paper slud ge PVC Polyviny l chloride SDRI Sealed double-ring infiltrometer TC Tire chips1



### 1.0 Introdu ction In May 1999, the U.S. Environmental Protection Agency (EPA) completed the Industrial D Tier 1 and Tier 2 groundwater tools to assist regula tors, industry, and the public in evalua ting the design o f Ind

ustrial Dwaste la

ndfills, su rface impoundme

nts, land a

pplication units, an

d waste piles. The se tools a

re described in the docume nt Guide for I

ndustrial W

aste Mana

gement (EPA 1999a). (More information on this document can be found at http://www.epa.gov/epaoswer/nonhw/industd/guidex.htm.) In June 1999, peer review on the Tier 1 a nd Tier 2 tools was completed and the tools were released for public comment. Pee r reviewers of the tools expressed concern that the me

thodolog y EPA used to e stablish the rates of leachate inf

iltration through lined waste manage ment units (

WMUs) did not conside

r expecte d variab ility

in liner pe

rforman ce. EPA is

in the process of revising the Tier 1 and Tier 2 tools and is considering incorporating distributions of infiltr ation ra tes for si ngle- a nd composi

te-lined units into the tools (some varia bility due to climate conditions is already inc orporated into EPA’s infiltration rate assumptions for single, clay-lined units).
In order to char

acterize and develop distributions for the infiltration rates through liners, an investigation was performed to: 1) assemble documents that describe the performance of nonhazardous (industrial and municipal) waste management unit liner sy stems (specifically, the

rates of leachate infiltration through liners); and 2) de scribe the magnitude and variability of infiltration through non-hazardous waste landfill, surface impoundment, and waste pile liners. The focus of this investigation was on collecting studies that descr ibe the performance of liners “as in stall ed” or “ as ope rated. ” The l iner t ypes cons idered are the follo wing:

C Single li

ners, inc luding c ompacte d clay liners (C CLs), geomem

brane ( GM) or fl exible membrane liners (

FMLs ), and g eosy

nthetic c lay

liners (G CLs)

C Composite liners, which include a geomembrane liner and a compacted clay

liner or geosy nthetic clay liner

C Double liners, whic h include two distinct liners, a

primary (top) an d second ary (bottom) liner, each of which are one of the types describe d above. Further description of these liner ty pes can be found in the Guide for I ndustrial W

aste Management

(EPA 1999a). This memorandum summarizes the investigation of infiltration rates through liners. I n Section 2, the literature survey

and results are described. Section 3 presents the infiltration ra tes and other relevant data acquired through the literature for the different liner ty pes. A summary and recommendations based on the infiltration data acquired ar e presented in Section 4.2



### 2.0 Literature Survey
2.1 Proce ss A literature survey was designed to identify and retrieve documents containing information on the performance of liners of landfills, surfac e impoundments, and waste piles. Specifically, document s on infiltr

ation ra tes throu gh liners were ta rgeted, though doc

uments we

re colle cted if they cont ained oth er infor mation re lated to th e perfo rmance of liners

. Data sources included the scientific literature, EPA re ports, and reports from other government and university sources. Electronic searc hes were conducted using the databases shown in Table 2.1-1. Additionally, the websites of the following organizations were visited and searc hed for relevant information:

C Interna

tional Ge osyntheti cs Societ

y (http://ig

s.rmc.c a/igs/inde x.html)

C Geosynthetics Institute (http://www.drexel.edu/GRI)

C Geosynth

etica (h ttp://geos ynthetic a.net)

C Tappi (http://www.tappi.org) A number of key

words and word combinations were used in the searc h to identify releva

nt literature:

C liner(s) and performance

C waste management unit and performa nce

C landfill(s) and performance

C surface impoundment(s) and performance

C waste pile(s) and performance

C liner(s) and leak

C landfill(s) and leak

C geosy

nthetic a nd liner( s)

C geosy

nthetic and leak

C geosy

nthetic and performance Additionally, once documents were obtained, the refer ence lists from those documents were reviewe d for pote ntial add itional sou rces. 2.2 Results A total of 132 documents were obtained and reviewe d for this project. A complete bibliography of all documents obtained and reviewed is contained in Appendix A. Of these documents, 65 were deemed relevant to the goal of the liter ature survey. Eighteen documents were found containing data on leak detection system (LDS) flow rates of double- lined landfills with a GM or3

composite primary liner. These are used to estimate leaka ge rates through such liners. Fourteen documents were found that contain information on calculated lea kage rates through holes and defects in geomembrane liners, including hole/defect fr equencies for landfills. One document was found containing infiltration rates through a GCL. For CCLs, 9 documents were found estimatin g infiltra tion rate s through t

he liner s using meth

ods such a

s lysimete

rs, infilt rometer s, and wate r balanc e. An add itional 19 d

ocuments were fo und conta ining info rmation on

hydrauli c conducti vity of co

mpacted clay line rs. Finally , five doc

uments we

re found that cont ain informat ion on the g

eneral perfor

mance e valuatio n of landf ills or sur face imp oundments

. These documents generally contained site and liner descriptions, and a de scription of the performance (and failure mechanism, if applicable), but no specif ic infiltration data. While gathering the literature, emphasis was placed on f inding information on infiltration rates through liners of actual, existing landfills as opposed to test plots or laboratory experiments. However, since a limited amount of information was available on infiltration through compa cted clay line rs at ac tual sites , literat ure was also colle

cted on te st plots. Mos

t of the inf

ormation i n the literature pertained to landfill liners; data on surface impoundments and waste piles was limited. Although the focus of this investigation is industrial and municipal waste, information on WMUs containing hazardous waste was also collected to provide a more comprehensive database. 

### 3.0 Infiltration and Other Relevant D ata This section presents the infiltration rates and other potentially relevant data collected from the lite ratur e, and is orga nize d by liner type. No i nform ation was fo und on infil trati on th rough double-lined landfills, therefore, this liner ty pe is not included.
3.1 Geomembrane and Composite Liners GMs (o r FMLs) ar e used to con tain o r preve nt was te con stit uents and le achate from e scapi ng a WMU. GMs are made by combining one or more plastic poly mers with ingredients such as carbon b lack, pig

ments, fil lers, pla sticizers , proces sing aids, cross- linking c hemicals , anti-degradants, and biocides. A wide ra nge of plastic resins are used for G Ms, including poly viny l chloride (PVC), hig

h density polyethy lene (HD PE), linea

r medium de

nsity polyethy lene (LMDPE), and chlorosulfona ted polyethy

lene (CSPE). Leakag e through GM liners can occur bec ause of permeation and due to defects in the liner itself. Lea kage f rom perme ation is sma

ll compar ed to lea kage f rom defe cts (Gir

oud and B onapart

e 1989a,b). There are three ty pes of defects ty

pically found in GM liners: pinholes, holes, and seam defects. Pinholes have openings significa ntly smaller than the GM thickness and a re caused by ma

nufacturing defects. Current manuf acturing processes have re sulted in pinholes being relatively

rare. Holes are openings that a re the same size or larger than the thickne ss of the GM. Seam defects are defective se ams resulting from fabrication or installation factors or se am failures caused by

excessive stresses during cover placement or facility opera

tion. Table 3.1-14

summarize s ty

pical de fects a

nd their li kely causes. For GM and composite liners, one of the best ways of estimating leakage ra tes is through LDS flow rates from double-lined systems with GM or composite top liners. The LDS collects and removes water beneath the primary liner of a double-lined landfill. The LDS flow rate can usually provide an estimate of the leakage rate through the liner. Other sources of LDS flows other than liner leakage are as follows (E PA 1998):
1. Construction water – water (mostly rainwater) that infiltrates the LD S during construction and continues to drain to the LDS sump after the start of facility operation. 2. Compression water – water that infiltrates the LDS during construction, is held in the LDS by capillary tension, and is expelled during waste placement as a r esult of LDS compression under the weight of the waste. 3. Consolidat

ion water – water e xpelled i nto the LD S from any CCL and/or

GCL components of a composite primary liner as a result of clay c onsolidation under the weight of the waste. 4. Infiltration water – water that percolates through the secondary liner and infiltrates the LDS. For all GM a

nd composi te liners

containe d in this re

port, inf iltration water is not an issu

e unless otherwise noted. All liners are either well above the w ater table or are constructed as to pre vent infiltra tion from groundwa

ter into th e LDS syste

m. For GM and GM/GCL liners, the only potential sources of water to the LDS are c onstruction water, c ompressio

n water, and leak

age thro ugh the pr

imary line

r. For ce lls with ge

onet LDSs, the construction and compression water are not applica ble since the geonet drains rapidly. For cells with sand LDSs, construction and compression water may be significant source s of LDS flows whi le the sa

nd LDS dra

ins (typic ally up to 1 year af

ter cell construc

tion). For GM/GCLs, consolida tion wate r is only a potentia l source if the GCL hydrate

s prior to w

aste fill ing, whic

h is contrary to the GCL installation procedures. For GM/CCL or GM/GCL/CCL composite liners, consolidation water can be a large contributor to LDS flows during and after waste filling, such that the contribution to the LDS flow from liner leakage cannot be determined. The portion of LDS flow attributable to leakage through the primary liner of a double-liner system would be leakage into the ground for a single liner system if the two liners have similar characteristics.5

3.1.1 Review o

f Literature In the literature review, two types of documents wer e collected in order to estimate leakage ra tes through G M and comp

osite line rs: 1. Those that contain data on LDS flow rates from double-lined landfills with a GM or composite primary liner.
2. Those that contain information on calculating the leakage rate s based on the frequency and size of defects in the GM liner. The primary source of data on LDS flows is EPA (1998). EPA’s repor t contains average and peak monthly LDS flow rates for 172 double-lined cells at 53 municipal solid waste (MSW), hazardous waste (HW), and industrial solid waste (I SW) landfills. It includes data for the initial period of operati on, activ

e period of opera tion, and p

ost-closure peri od. Seven other se parate document s were f ound that u

se or summa

rize some of the sa me data th

at is conta

ined in EPA (1998). T hese inc

lude: Bona

parte ( 1995), Bon

aparte and Gros s (1990), Bonapar

te and Gr oss (1993), G ross et a

l. (1990) , Othman e

t al. (199 7), EPA (1 992), an

d EPA (199

6). In ad dition to the EPA (1998) report, 9 other documents were found that c ontain LDS flow data: Bergstrom et al. (1993), Eith & Koerner (1997), Feeney & Maxson (1993), Gia rdino & Guglielmetti (1997), Maule, et al. (1993), Phaneuf (no date), Reddi & Scarlatos (1996) , Tedder (1997), and Workman (1993). The data from these documents is presented in Section 3.1.2. Fourteen documents were found pertaining to calculation of lea kage rates based on the frequenc y and size of defects in the GM liner. Four documents (Giroud & Bonapar te 1989a,b; Bonaparte et al. 1989, and Giroud et al. 1992 ) prese nt methods

for per forming th is calcu lation alo ng with some estimated leakage rates. Eight documents provided information on hole/defe ct frequencies for land fills: Darilek et al. (1989), Laine (1991), Laine & Da rilek (1993), Laine and Miklas (1989), McQuade and Needham (1999), Mosley a nd Crozier (1995), Peggs (1993), and Rollin et al. (1999). Two documents present leakage ra tes through holes in liners: Wilson-Fahmy and Koerner (1995) and Hartley (1992). The data from these documents is presented in Section 3.1.3.
3.1.2 Leak Det

ection Sy stem Flow D

ata The LDS flow rates from all documents were compiled into Table 3.1- 2. The average, minimum, and peak monthly LDS flow rates along with the characteristics of the landfill, liner, and LDS system are presented. A total of 259 landfill cells with LDS flow rates we re found from the literature. Since the focus of this report is on infiltration rates during the W MU’s active period of operation, when possible, only LDS flows during this period are reporte d in Table 3.1- 2. The ac tive per iod of ope

ration is d efined a s the per iod during

which the

cell is fi lled with waste and daily and intermediate layers of cove r soil; this period begins after construction water has substantially drained and its contribution is now minimal. For cells reported by EPA (1998), this period excludes the first few months of waste disposal until the leachate collec tion and6

removal system (LCRS) flow rates stabilize. For other data sources, the ac tive period of operation may exclude time required for dra inage of the sand LDS; these are noted in the Notes column. For

all other data sour ces, the active p eriod of operati on include

s some or a

ll of the ti me of waste filling unless otherwise noted. The duration of the excluded pe riod, called the initial operating period, is provided in the table. Additionally, one document (Phaneuf , no date) reports measured leakage rates from modern New York landfills ranging from 70 to 112 liters per hec tare per day

(lphd), but no information on specific landfills is reported. These double-lined landfills contain a primar y composite liner constructed under a comprehensive CQA prog ram. Due to the lack of specific liner information, this data is not included in Table 3.1-2. The parameters represented in Ta ble 3.1-2 were selected because they potentially

have a significant relationship with the LDS flows. Table 3.1-3 lists the parameters identified for each site and the percent of sites reporting the par ameter. Of the 26 identified parameters, 16 contained data for over 70 perce nt of the cells. For the most part, information about the cell and liner (e.g., location, liner ty pe and thickness, LDS ty

pe) was more likely

to be reported than more general site data (e.g ., rainfall, depth to groundwater, subsurfac e soil type). I nformation on the specifics of the LDS sy

stem (e.g., flow measurement method) was a lso lacking. The ty

pes of data reported were similar across a ll liner types, except the GM/GCL liner, which tended to have more dat a repor ted. This i s due to the

fact tha t most of the

GM/GCL

cells ar e from the

same dat a source. It should be noted that some documents contained time-variable infiltration during the operati onal per

iod. Since the Indus trial Wa ste Mana gement Ev

aluation Model (I WEM) (EP

A 1999b,c) for which these data are intende d, cannot handle time-varying infiltration, Table 3.1-2 contains only the average, minimum, and peak LDS flow rates over the entire active period of operation. To addre ss the time -varia bility issue, a l imited amo

unt of dat a on ave rage m onthly LDS flow rates for landfills during the post-closure period was compiled from the same source s as the LDS flows for the opera ting period. This data is provided in Table 3.1-4. The post-closure period is defined as the pe riod duri ng which a final

cover sy stem is in pl ace. The landfi ll cells for the covered landfills overlap the cells provided in Ta ble 3.1-2, and the first column of each table can be used to cross-refer ence information. When mor e compre hensive t ime-var ying data was rep orted in d ocuments , the data are pro vided in A ppendix B.
3.1.2.1 A nalysis of Scop e of Data
In order to determine w

hether the LDS flow data f ound in the literature represent the differe nt typ es of la nd fi ll s f

ou nd ac ro ss th e U .S ., th e d at a w er e a na lyz ed by:

C Liner ty

pe

C Liner/L

DS system combination

C Waste type and re gion combination

C Land

fill waste placeme nt start da te7

C Level of construction quality assurance (CQA) employ ed
The LDS flow data found in the literatur e represent 5 different liner ty pes: GM (33 percent), GM/CCL (55 percent), GM/GCL (11 percent), GM/GCL/CCL (1.5 percent), and GM/GCL /GM (0.5 percent). Generally

, the GM, GM/CCL, and GM/GCL liners are well represented, with over 30 cells each. The GM portion of the liners are primar ily HDPE (90 perce

nt), with 4 percent CSPE, 4 percent PVC, and 2 percent LMDPE. The ty pe of GM material is potentially sig nificant to the infiltration rate through the liner because of dif ferent installation techniques; CSPE liners are typica lly installed using solvent seaming while HDPE liners are ty pically installed using thermal seaming. The distribution of the LD S flow data by GM mater ial and liner type is shown in Figu re 3.1-1 . HDPE is the

only GM ty pe well r eprese nted in al l the liner

typ es. LMDPE liners (4) are only

found in GM/CCL liners, PVC liners (10) are only found in GM liners, and CSPE liners (9) are only found in GM liners except for 1 GM/CCL liner. The type of L

DS drainage material is important in determining the infiltration ra te through the liner fr om LDS flows bec ause ce lls with san d LDSs have a su bstantial ly la

rge potential to

releas e construc tion and c ompression water t o the L DS over time, espec ially

during i nitial and early active periods of cell operation. By contrast, geonet L

DSs drain rapidly. The L

DSs for the landfill cells are primarily geonet (53 percent) and sa nd (29 percent). Figure 3.1- 2 shows the distribution of LDS flow data by liner type and L

DS type. For GM liners, all the LDSs are composed

of sand, geonet, or

a combina

tion of the

two. For the GM/CCL

liners, geonets dominate the LDS ty

pes with some sand a

nd gra vel/ge onet sy

stems. Figure 3.1-3 presents the L DS flow data by ty

pe of waste and U.S. region. The re gions are based on the regions defined by EPA (1998), which were selected beca use of the climatic differences between the regions (i.e., aver age annual rainfall, potential evapotra nspiration, and days below freezing ). The re gions ar

e define d as follows:

C Northeast: All states north of and including Missouri, Kentucky , West Virginia, and Mary land and e ast of an

d includin

g Wiscons in, Il linois, and Missouri.

C Southeast: All states south of a

nd includi

ng Arka nsas, Te nnessee , and Vir

ginia, a nd east of and inc luding A

rkansas and Texas

.
C West: All states west of and including Minnesota, I owa, Kansas, Oklahoma, and New Mexico.
As demons trated in

the fig ure, the landfill c ells are

mostly MSW cells loc ated in the Northe ast. This is not unexpected since the Northeast is rather densely populated and several states in the Northea st requir

e double l iner sy

stems for MSW landfill s. The da

ta collec ted was sp arse for ISW landfills (5) and Western landfills (13), and therefore, should not be consider ed representative of these types. I

n general, however, the ty pe of waste and climate do not have much influence on the infiltration rate through a GM or composite liner; infiltration rates usually depend more on liner system construction and pe rformance.8

The L DS flow da

ta collec ted is ge nerally repres entative

of moder n landfill s (constr

ucted wit hin the last 15 years). Figure 3.1-4 shows the distribution of waste placeme nt start dates. Most of the landfills had initial waste placement between 1987 and 1992. Modern landf ills tend to be construc ted with st

ricter g uideline s than olde

r landfil ls. The use of formal CQA procedures ca n have a significant influence on a liner ’s tendency to leak due to faulty construction, and therefore, the infiltration rate through the liner . Figure 3.1-5 shows the distributi on of L

DS flow da

ta by CQA proc edure a

nd liner ty

pe. As de monstrate d in the figure, nearly

all of the cells in the database have been construc ted with a formal CQA progra m. 3.1.2.2 A nalysis of L

DS Flow Da

ta As discussed at the beginning of this section, the significa nce of LDS flows varies f or different liner types. Ther

efore, the data in Table 3.1-2 is groupe d by liner ty pe, and the LDS flow rates are anal yzed sim ilarl y. The min imum , max imum , mean , and m edian value s of th e average monthly LDS f lows are shown for

each liner ty

pe in Tab le 3.1-5. For those sites whic

h only reported weekly

or daily aver

age LDS flow (

noted in Table 3.1-2), the data were excluded from calculation of these parameters. Cumulative distribution functions of the avera ge monthly L

DS flow rates are presented by liner type in Fig

ure 3.1-6. As discussed previously, the L DS flow rates for GM, GM/GCL, and GM/GCL /GM liners can generally be considered representative of the le akage through the liner. F or landfills with a sand LDS, this is true after drainage of the sand which generally takes less than a ye ar. For most of the landfills with sand LDSs reported in Table 3.1-2, the a verage L DS flows are reported for the period after this

initial dr ainage period. F or a few

landfill c ells, it is u

nknown whether th

is period is included in the average or not; this is noted in the table.
The LDS flow rates for the GM/CCL and GM/GCL/CCL liners represent leakage thr ough the liner in a ddition to c onsolidat

ion water . When a cl ay

liner is c ompacte d during construction, it may be very nearly saturate d when compaction is complet

e. When the

clay is then sub

ject to compres sion loadi

ng, such as fillin

g with waste, the a

ir voids wi ll first be

lost and then wate

r will be expelled from the water-filled voids. The amount of and rate a t which the water is expelled due to consolidation is a function of the consolidation characteristics of the compac ted clay, the thickness, and the load placed upon it. Several papers pre sent methods for estimating volumes of consolidation water. Gross et al. (1990) present a method for c alculating the maximum rate of water expelled from a consolidating clay layer subjec

t to a constant rate of load application, and indicate that almost all the consolidation water will be expelled at the end of waste placeme nt. Feeney and Maxson (1993) present a model designed to calculate the volume of fluids expelled by t he prima ry clay liner und er simula ted waste loading condition s. The mod

el was compared t

o actual flow rate data from landfill cells and g enerally ma tched the pattern and magnitude. Bergstrom et al. (1993) use a c onventional approach to estimate volumes of consolidation water. These estimates are compared to actua l LDS flows from landfill cells, and indicate that9

co ns ol id at io n w at er ca n b e e xp el le d l on g a ft er lo ad in g o f a la nd fi ll ce ll ce as es . A dd it io na ll y, Bergstrom et al. (1993), EPA (1998), and Workman ( 1993) use chemical characteristics of the LDS f lows to ass ess whether leak age is o ccurri

ng throu gh the primary

liner; however, these methods are not used to quantify leakage rates. While these methods may provide estimates of consolidation water volumes produced by a GM/CCL or GM/GCL/CCL liner or whether or not leakage is occurring , they are not accurate enough to provide informa tion to determine actual rates of infiltration through GM/CCL or GM/GCL /CCL liners due to leakage a lone. One pote ntially important

parameter in ter

ms of the e ffect on the lea kage r ate thro ugh the liner is the CQA pr

ocedure s employ

ed. For the LDS flow da

ta, 95 per cent of t he data was repor

ted with an assessment of the CQA procedure. For the most part, a formal CQA program was employ ed. Table 3. 1-6 compa

res the statistics o f the ave rage m onthly LDS f low rate s for all c ells, ce lls constructed with formal CQA procedures, and ce lls constructed with no formal CQA procedures. Table 3.1-6 is organized by liner type; only

GM and GM/CCL liner ty pes are reported, since for all cells with other

liner ty pes, only formal CQA proce dures we re followed. As de

monstrate d in the table, the LDS flows are hig her for cells constructed with no formal CQA prog ram for GM liners. However, for GM/CCLs, the opposite is true, whic h is contrary to finding s in the literature (e.g., EPA 1998). Also, the differe nce between LD S flows for landfills constructed with good CQA and all cells is negligible. The c onflicting results are likely a result of the fact that ther e are f ew cells in the dat

abase c onstruct

ed withou t a forma l CQA prog

ram. The LDS flow measurement pe riod is important in determining whether the data are representative of a ty

pical landfill’s operational life. For some landfills, the L DS flows may have been measured for the entire oper ational life, while for others, LDS flows may have been measure d for only

a subset o f the ope

rationa l life. Th is informa

tion was g eneral ly not availa ble in the literature; only the pe riod of measurement was reported. Table 3.1- 7 presents the mean, median, minimum, and maximum of the reported LDS flow measurement per iods by liner ty

pe. Cumulative distribution functions of the LDS flow measurement periods are presented by

liner type in Fig

ure 3.1-7. In g eneral, the flow measurement periods are similar for the major liner typ es, and a

verag e about 2- 1/2 y

ears. Table 3.1-8 provides the statistics of the average monthly L

DS flow rates by liner

type for the landfills during the post-closure period. I n general, the average monthly L DS flows during the post-clo sure per

iod are s ignific antly

less than the LDS flows du

ring the operati ng per iod. This is expected , since the amount o f water reachi ng the li ner is limit

ed by the cove r. For the GM/GCL liner, however, the mean, median, and maximum LDS flow r ates during the post-closure period are slightly

larger than the L

DS flows during the operating period. This is due to a combination of two fa ctors: 1)the data

are limite d for GM/GCL line rs; and 2) the fact that for

the one la

ndfill cell (G231) with the highest flows during the post-closure period, the LDS flows are hig her during the operating period than during the post-closure period.
3.1.3 Calculated Leakage Rates10

Numerous studies have been performed to evalua te the frequency

and size of holes and other leaks in GM liners using electrical leak location surve ys (Darilek e

t al. 1989; Laine 1991; L aine and Darilek 1993; Laine a nd Miklas 1989; McQuade and Needham 1999; Mosley and Crozier 1995; Peggs 1993; Rollin et al. 1999). In an e lectrical leak location survey, an electrical power supply is connected to ele ctrodes above and below the liner. When no leaks are present, the voltage impressed across the liner produce s a very low c urrent flow and relatively uniform voltage distribution in the material above the liner. Holes in the GM are indica ted by anomalies in the potential gradient caused by the electrical current flowing throug h the hole. Table 3.1-9 presents the leak densities from the leak loca tion surveys presente d in the literature. The leak density f

or 247 sites is presented along with the range of hole size, characteristics of the leaks, and characteristics of the waste ma nagement unit, when available. Note that data f rom Darilek et al. (1 989) was

excluded f

rom the ta

ble beca use it is be lieved to

be the sa me data a s in Laine and Miklas (1989). Additional information on leak de nsities is presented in Mosley and Crozier ( 1995) whi ch is also not includ

ed in Tab le 3.1-9. This data is prese nted for 169 sites in the form o f a gra

ph of the n

umber of sites surveyed versu s the lea k density . No site- specific informat ion is provided, and

the data is not pre sented in

a form tha

t would be

easily convert ed to a table. The average

leak density from this data is re ported as 22.11 leaks/ha. The leak densities range from 0 to 774 leaks pe r hectare, with a mean of 43 leaks per hectare. Figure 3.1-8 shows the cumulative distribution of leak density values, which have a median value of 8.2. These leak densities appear to repre sent a range of site sizes (90 to 67,100 m 2 ). Of the 124 sites where the leaks were fully broken down by lea

k type, 78 perc ent were identified as holes, 9 percent were identified as knife c uts or tears, and 13 percent were identified as seam or weld defects. Inf

ormation that may potentially be related to the leak density (e.g., the ty

pe of waste and WMU, CQA procedures, liner ty pe) is limited. Table 3.1-10 presents the mean, minimum, maximum, and median leak densities for all cells, cells with good CQA procedures and cell s with HDPE

liners; a nalysis by other fa ctors wa s not perf

ormed due

to the limite d data available. The table demonstrates that the leak densities at ce lls constructed with a formal CQA progra m and cel ls with HDPE

liners ar e signif icantly less than the leak densities for all si tes. A small amount of data on leak densities for GMs covered with soil covers was found in the literature. Assessment of leaks after place ment of the soil cover is important since, during cover placeme nt, the line

r can be damage d by

the equipment used

to place the cove r, tools us ed to spread the material, sharp rocks in the soil, or other mecha nisms. Leak survey

s of soil-covered GMs are more difficult than uncovered liners bec ause 1) inhomogeneities in the soil cover may reduce the signal streng

th, 2) the re is a de crease d ability

of the el ectrode s to detect leak sig nals because of the dis similarity

of the soi l and wate

r medium, a

nd 3) the probe ca

nnot be use d close to the GM liner (Laine and Miklas 1989). I nformation was found on two specific sites where leak location survey s were made on soil-covered GMs (Dar ilek et al. 1989; Laine and Dar ilek 1993) and on leak densities for 17 additional sites (Mosley and Crozier 1995). Table 3.1-11 presents a distribution of leak density c ompiled from all sources.11

Significantly less data

was found in the literature on the sizes of the leaks (Table 3.1-12). A s demon strat ed in t he tab le, in general , onl y ranges of l eak si zes we re repo rted. Not en ough information was presented in the literature to develop a distribution of leak size. A method for calculating leakag e rates through defects in GM and c omposite liners is presented in Bon aparte et al. (1989 ), Gir oud an d Bonap arte (1 989a, b), an d Giro ud et a l. (19 92). Leak age through GM holes is

consider ed via the following

cases: Geomembrane Alone. If a GM with a hole is ove

rlain an d underla in by high-pe rmeabili ty materials (such as a geonet or c oarse gravel), flow throug h the hole is not significantly impede d. In this case, flow can be

considered as free flow throug h an orifice, which can be evaluate d by Bernoulli’s equation (Table 3.1-13). Geomembrane Composite Liner. If a GM with a hole is plac ed on a la ye r of low- permea bility soil to for m a compos ite liner , the low- permea bility soil sign ificantl y imp edes the

flow of li quid through the hole, provided that the GM is in close contact with the low-perme ability soil. I t has been shown that it is nearly impossible to achie ve such close contact as to prevent lateral f low betwe en the GM and under lying soi l, and that a key factor in in fluen cing th e rate o f leaka ge through a composi

te liner i s the qual ity o f contact betwee n the GM a

nd low-pe

rmeabili ty s oil (Giroud and Bonaparte 1989a). Two e mpirical equations were developed based on a me thod of interpolation of experimental and theoretical results on contact quality (Bonaparte et al. 1989); these equations are shown in Table 3.1-13.
Geomem brane Ov

erlain by Drainage

Material. If a GM wit h a hol e rest ing on a high permeability mater

ial is overlain by medium-per meability drainag e material, such as sand or fine gravel, flow through the hole may be somewhat impeded. Bonaparte et al. (1989) present an empirical equation to represent this situation (Table 3.1-13). Using the equations presented above, leaka ge rates were ca

lculated for the three ty

pes of liners discussed above. Since information in the literature on hole sizes is limited, calculations are perfor med for two hole size s, 3.1 mm 2 and 1 cm 2 . This is based on the recommendation by Giroud and Bonaparte (1989a) to use the smaller hole to size the components of the lining system and the larger hole to evaluate pe rformance. For the composite liner, the conductivity of the lowpermeability soil was assumed to be 10 -7 cm/s; for the GM overlain with a drainage mate rial, the conductivity of the dra

inage material was assumed to be 10 -2 cm/s. Calculations were performed for several liquid depths, using the mean and median hole fr equencies, 43 leaks/ha and 8.3 leaks/ha respectively , as discussed earlier in the section. The calculate d leakage rates are present ed in Tab les 3.1-1 4 and 3.1- 15 for the 3.1 mm2 and 1 cm 2 ho le si ze s, re sp ec ti ve ly. Additionally, Wilson-Fahmy and Koerner (1995) present a finite diff erence method for calculating the leakage

rate through a hole in a GM overly ing a GCL. Wilson-Fahmy and Koerner investigated the influence of factors such as the transmissivity at the contact between the GM and GCL , the hole

size, the h

ydr aulic conductivity

, and the t hickness of the be ntonite12

component of the GCL. The transmissivity was determined to have the most significant effe ct on the leak age ra tes. Tabl e 3.1-16present s the lea kage r ates by transmiss ivity

and cond uctivity calculated for a 0.8 cm 2 hole and a GCL thickness of 7 mm.
3.1.4 Comparison of Actual and Calculated Leakage Rates Table 3.1-17 compares the actual versus ca lculated leakage rates throug h GM liners as presented in th e previ ous t wo sect ions . The ac tual l eakage ra tes ar e comp ared to the cal culat ed leak age rates for the GM overlain w ith draina ge mate rial, sinc e nearl

y a ll of the G

M liners in

the data base have a L CRS compose d of sand or a sand/ grave l combina

tion. Since

the depth of the liqu

id is not known, the range of calculated le akage rates over the r ange of liquid depths analy zed is used for the comparison. For both the mean and median value s, the actual leakage rate s are on the lower end of the range ca lculated for the smaller hole size. For GM/GCL liners, an ade quate comparison between actual and ca lculated leakage rates c annot be made, because the leak density data only apply

to GM liners. However, in comparing the calculated leakage ra

tes through a single hole (7,300 to 10 -7 lphd) to the actual leakage rate s (mean of 3.9 lphd), it is clear that the calculated leaka ge rates are much larger that the actual leakage rates. Comparisons between actual and calculated lea kage rates are not made f or GM/CCL liners, since the actual leakage rate

for these liners can not be determined from L DS flows.
3.2 Geosynthetic Clay Liners A GCL is a factory

-manufactured, hy

draulic barrier ty

pically consisting of be

ntonite clay (or other ve ry low perme ability

materia ls), supported by

geotexti les and/or geome mbranes held together by

needling, stitching, or chemical adhesives. GCLs are ty pically used in are as where clay is not rea

dily available or whe

re conserving air space is a n important factor. GCLs do not have the level of long-te rm field p erforma

nce data that are availab le for GM s or CCL s becaus e GCLs were develope d recently ( 1986) and they a re typically

used with a GM in a composite liner system.
3.2.1 Review o

f Literature Only one document was found during the literature survey that discusses the performance of GCLs when installed as a single in-se rvice liner (Lichtwa

rdt and Comer 1997). Numerous other documents on the GCL technology and laboratory

experiments on different type s of GCLs are available in the literature; these were not ac quired since they are bey ond the scope of this report.13

3.2.2 Performa nce Data In the single document on GCL performance (Lichtwardt and Comer 1997), a GCL was installed on the bottom of a salinity-gr adient solar pond in Texas in 1994. The pond has a surface are a of approxima

tely 1 acre a nd a wate r depth a veraging 3.2 me

ters. The GCL is a modifie d Gundsea

l, with a 30-mil flexible polypropy lene geomembrane backing with 0.5 cm of bentonite clay bonded to one side. The per

formanc e of the G CL is pr esented as the va riation in hyd raulic conductivity of the GCL

over time for a 9-week period. The hy draulic conductivity re

mains fairly constant a

t 2 x 10 -6 cm/s. This represents an increase over the initial conductivity, which was measured at 1 x 10 -6 cm/s. The data presented in this paper represe nts the unique environment of a salinity-g radient solar pond (which includes high temperature , high salinity and low pH), which may not be representative of GCL

use in other situations.
3.3 Compacted Clay Liners CCLs are composed of natura l mineral materials (natural soils), bentonite-soil blends, and other materia ls place d and comp acted in layers cal led lifts. CCLs c an be de signed t o work ef fective ly as hydraulic ba

rriers, assuming that selected liner materials a re suitable, liner materials are properly plac ed and compacted, and the completed liner is proper ly protected be fore, during, and after construction. For CCLs, pe

rforman ce eval uation usu

ally cons ists of mea

suring the field hyd raulic c

onductivi ty of the liner. The two most common methods used to estimate the hydraulic conductivity are collecti on lysimete

rs and inf iltromete rs. Both of

these me thods mea

sure the infiltra tion rate through the CCL and use it to calculate the conductivity. Lysimeters are collection basins installed beneath a portion of the line

r. Wate r that inf iltrates through th

e liner a bove the b

asin is collected and routed via pipes for discharge me asurement and chemical analysis. The infiltration rate through the CCL can be determined by dividing the discharge by the a rea of the lysimeter. A long period of monitoring (several weeks to several months) is require d in order for the collection lysimeter to give steady-state infiltration rates. At least one state, Wisconsin, re quires lysimeters for monitoring of landfill performance. Infiltrometers direc tly measure the infiltration rate through the portion of the liner over which they are installed. Although there are several types of infiltrometers, the sealed double-ring infiltrometer (SDRI), a sea led ring or box that measures infiltration into a relatively large area, is the most appropr iate for reliably measuring low hydraulic conductivities that are representative of the entire liner. Infiltrometers are installed and the test pad flooded and then infiltration rates through the infiltrometer are measured. SDRIs also require a long period of monitoring (several wee ks to several months) to ensure that the infiltration rate has reached steady-state. Mor e details on these methods can be found in Daniel (1989) and Sai and Anderson (1990). One additional method of determining leakage through CCLs is the water balance method. The water balance method involves using the rainfall, evapor ation, and pond filling rate to determine leakage through th

e liner. Drawba

cks to this m

ethod inc lude pote ntial prob lems with a

ccurat ely measurin g the amou nt of rain

fall and evapora tion that oc

curs.14

3.3.1 Review o

f Literature
In the literature re

view, documents were collected that contained infor mation on infiltration rates and hy draulic conducti vities of C CLs. T

here wa s often overlap of infiltra tion and c onductivi

ty data in these sour

ces, as f ield infil tration r ates ar e used to c alculate

the field hyd raulic conducti vities. The compar

ison of fie ld to lab hy

draulic conducti vity is a topic t

hat is hea vily discussed in the literature, so the documents collected often contained both fie ld and lab values of hy draulic conducti vity . Docume

nts that co

ntained only

laborat ory values of hyd raulic conductivity were

not collected and reviewed. A limited amount of data was found on infiltration rates through CCL s. Even though infiltration data is often collected during testing for hydraulic conduc

tivity, the infiltration data is often not reporte d in the lite

rature . Most of the source s with infil tration da ta also re port hy draulic conducti vity : Albrecht and Car

twright (1989), D aniel (1 984), Gor don et al. (1989), K

ing et a l. (1993), Rogowski (1985), O'Sadnick et al. (1995) , and Trautwein and Williams (1990). Two additional sources were collected that contained infiltra tion data only: Cartwrig

ht and Krapac (1990) a nd Huebne

r and Gor don (1995 ). The da

ta on infil tration r ates from these do cuments is presented in Section 3.3.2.
Data on f ield hy draulic conducti vities of C CLs ar

e much mor

e preva lent in the literatu re. This i s because conductivity

is the key perf

ormance parameter found in reg ulatory documents. The primary source o f CCL h

ydr aulic conductivity

data is EPA

(1998). T

his repor t contain s a database of 89 CCLs (8 in-servic e and 81 test pads) with hydr aulic conductivity and other propert ies of lan dfill line rs. This r eport al so contai

ns a smalle

r databa se of fie ld hy

draulic conducti vities for 11 test pa

ds that ha d bentonit

e added to the nat ural cla y so il. Six separ

ate documents were found that use or contain the same data in these databases: Benson et al. (1999), Bergstrom et al. (1995), Gordon et a l. (1989), Johnson et al. (1990), O'Sadnick et al. (1995), and Reades et al. (1990) . Benson and Daniel (1994) contains data on field hy draulic conductivity for CC Ls, s om e of

whi ch o ver lap wit h l in ers fro m EP A (1 998 ) an d ot her sou rce s co ll ect ed. In addition to the EPA (1998) report and the other refere nces listed above, 9 other sources were collected containing hy

draulic conductivity data : Albrecht and Cartwright (1989), Day and Daniel (1985), Daniel (1984), Elsbury et al. (1990), Gordon et al. (1984), L uettich et al. (1995), Rogowski (1985), Trast and Benson (1995), and T rautwein and Williams (1990). The data from these documents is presented in Section 3.3.3.
3.3.2 Infiltratio n Data
Infiltration data for CCL s is presented in Table 3.3-1. A total of 9 sites were found from the literature: 2 ponds, 3 landfills, and 4 test pads. The average infiltration rates range from 1.6 x 10 -9 cm/s to 1.2 x 10 -6 cm/s, with an average of 3.1 x 10 -7 cm/s. The period of measurement ranges from 40 day

s to 13 years. I

n general, the measurement per iod is shorter for test pads (40 days to 2 y

ears) than for the actual sites (90 day s to 13 years). The

measurement methods used are infiltrometers, ly simeters, and water balance; eac h was used at three of the sites reported. For15

the water balance and infiltrometer methods, a dire ct infiltration rate is typically reported. For the lysimeters, a volume collec ted per time period and the ly simeter area are reporte d; the infiltration rate is calculated from this data. O'Sadnick et a l. (1995) also present time-series infiltration data from 60-day infiltrometer tests at a landfill site; this data is not reported in the table because no averag e infiltration rates are given in the text. Over the 60-day testing period, infiltration rates range from 10 -9 cm/s to 2 x 10 -7 cm/s. Due to the limite d amount of

data available on infiltration rates, these data are not nec essarily re presentative of infiltration rates through CCLs across the U.S.
3.3.3 Hydraulic

Conductivity Data Hydraulic conducti vity values f rom all co llected s ources a re pres ented in T able 3.3- 2. Field hydraulic conduc

tivity values, along with site cha racteristics, liner characteristics, and lab hydraulic conduc

tivity values, where a

vailable, appear in the table. A total of 149 liner sites were found in the literature. Of the 149 liner sites, 11 are in-service waste management units, 120 are test pads , and 18 a

re not re ported a s one or the other. Of the 11 in-service units, 8 are la ndfills and 3 are ponds. The parameters appearing in Table 3.3-2 were selected beca use they potentially

have a significant relationship to the hydraulic c onductivity values. Table 3.3-3 lists the per centage of sites reporting each of the para meters. Less than 10 perc ent of the sites report construction date or monitoring period. All of the liner characteristic par ameters except for the clay fraction are reported for at least 60 percent of the sites. All of the construction parameters are repor ted for 50 to 75 perc ent of the

sites. Among the q

uality assuran ce para meters, a ll are re ported f or at lea st half of the sites wi

th the exce

ption of f requenc y of moisture d

ensity tests, whi ch is rar

ely reported. The laboratory

hydraulic conduc

tivity is reported for 72 per cent of liner sites.
3.3.3.1 Analysis of Scop e of Data
In order to determine w

hether the data found in the literature repre sent the different ty pes of CC Ls f ou nd ac ro ss th e U .S ., th e d at a w er e a na lyz ed by:

C Liner ty

pe

C Region

C Level of CQA employ ed The largest amoun

t of data was foun d for test pads, wh

ich compr

ise 120 out

of 149 line

r sites in the database. Data on in-service CCL s is limited likely due to the fact that CCL s are often used in conjunc

tion with GM

liners an d few in- service

CCLs a re usual ly c onstruct

ed with instruments allowing document

ation of their per

formanc e. Ther

e are 13 7 natura

l clay liners in t

he datab ase and 12 soil/bentonite liners. Because of the sparse data on soil/bentonite liners, the data is not necessarily

representative of this liner ty pe.16

Figure 3.3-1 presents the number of CCL sites by U.S. region. (The regions are were defined earlier in Section 3.1.2.1.) The figure shows that the da tabase contains the most data for liner sites in the

Southeast . The lea st number of sites oc cur in the

West (15), despite the fact that this is the largest geogr

aphic region. Note that only 56 percent of sites report location data.
The use o f formal

CQA proc edures c an have a signif icant inf luence on the line

r’s fiel d hy

draulic conductivity. Of the 149 liner sites, 69 pe rcent were constructed with a forma l CQA procedure, 5 percent were not, and this information was not reported f or 26 percent of the sites. Note, however, that the database in EPA (1998) only included liners that were constructed with CQA in gene ral acc ord with in

dustry practic es; liners constru

cted with poor CQA were spe cifical ly excluded from this report. Also note that some of the liners found in the literature were documented because of the fact that they experienced greater lea

kage than expected, in part because of insufficient CQA.
3.3.3.2 Analysis of Hy

draulic Conductivity D ata The mean, median, minimum, and maximum values of field hydra ulic conductivity are show n for natural clay , soil/ben

tonite, a nd all line rs in Tabl e 3.3-4. These sta tistics ar e shown f or landf ill sites, pond sites, test pads, and all liner sites in Table 3.3-5. Though there are limited data for landfills, the average hy

draulic conductivity for

these in-service units is an order of magnitude lower than the average hy draulic conductivity for

the test pads. The lower conductivity may be a result of several factors, including 1) the c ompressive stress on in-place liners is much higher than on test pads due to waste loading which may result in a lower conductivity; and 2) the inservice liners are gene

rally thicker tha

n the test pad liners. As discussed previously , there is not enough data to character

ize soil/bentonite liners, landfill liners, or pond liners separately . For the purpose o f develo

ping a d istribution of field

hyd raulic c onductivi

ty, it may be appro priate to use all of the data as characteristic of CCL s as a general class.
A cumulat

ive distri bution fun

ction of a ll field hy draulic conducti vity values c ollected

for this study is presented in Fig

ure 3.3-2 . The common regulatory criterion of 10 -7 cm/s is also shown on this figure. The figure illustrates that 70 per cent of liner sites reviewed for this study have a field hydraulic c onductivity value of less than or e qual to 10 -7 cm/s. Figur e 3.3-3 presents

a scatte r plot of f ield versus labor

atory hyd raulic c onductivi

ty values. Th

is plot also shows lines representing several ratios of lab to field va lues. The figure shows that most of the data lies below the 1:1 line, which means that laboratory tests usually under-pre dict field values of hydr

aulic conductivity. Additionally, most of the points lie above the 0.01:1 line (field values of conductivity 100 times greater than lab values), but the plot shows a value of field conductivity as much a s 4 orders of magnitude grea ter than the corresponding lab value. The reliability of labor

atory hy draulic conductivity tests in predicting field values is a topic that is heavily discussed in the literature (e.g., EPA 1998, Trast and Benson 1995). The observations made here concur with those found in the literature. I t is generally

believed that laboratory measure ments, whi ch occu

r on a sma

ll-scale , will y

ield the sa

me conduc

tivity as field17

measure ments, whi ch occu

r on a lar ge-sc ale, if the clay

liner is w ell-con structed

and rea sonably homogeneous; the reverse is also believed to be true

. 

### 4.0 Summary and R

ecommendations
4.1 Geomembrane and Composite Liners For GM and composite liners, infiltration rates through liners were estimated from LDS flow rates from double-lined landfills with a GM or composite primary liner. No information was found on in filt ratio n rates for su rface i mpou ndmen ts or w aste p iles. A data base o f avera ge monthly L

DS flow data was compiled which contains 259 landfill cells. The database c an be summarize d as follows:

C Generally , the GM, GM/CCL, and GM/GCL liners are well represented, with over 30 cells ea ch. HDPE i s the only

typ e of GM ma

terial w ell repr

esented in all the l iner ty

pes.

C Both san

d and ge onet L

DSs are well repr

esented for GM an

d GM/CCL

liners.

C The LDS data primarily represent MSW cells located in the Northeast. The data collected was sparse for I SW landfills and Western landfills and therefore, should not be considered representative of these ty pes.

C The LDS flow data collecte d is generally representative of modern landfills. Most of the landfills had initial waste placement between 1987 and 1992.

C Nearly

all of the cells in the database have b een con structed with a for

mal CQA pr

ogram. The information on average monthly LDS flows from the landfill database is summarized as follows:

C The LDS flow rates for G M liners range from 1 to 4,282 lphd, with an average of 258 lphd . Thes e flow rates can gene rally be co nsid ered re presen tati ve of t he leak age thro ugh the liner.

C The LDS flow rates for G M/GCL liners range f

rom 0 to 32 lphd, with an average of 4 lphd . Thes e flow rates can gene rally be co nsid ered re presen tati ve of t he leak age thro ugh the liner.

C The LDS flow rates for G M/CCL liners range from 0 to 1410 lphd, with an ave rage of 130 lphd. LDS flows for these liners ty pically repr

esent leakage through the liner plus conso lidat ion wa ter. A ctual rates of inf iltr ation throu gh GM/C CL line rs due to lea kage alone cannot be determined.

C An analysis of the da ta by CQA level showe d conflicting results, likely due to the fact that few cells in the database were constructed withou

t a forma l CQA prog

ram.

C A limited amount of data on LDS flow rates for la ndfills during the post-closure period was also compiled. In ge neral, for GM and GM/CCL liners, the a verage monthly

LDS flows during the post-closure period are sig nificantly less than the L

DS flows during the operating period.18

For GM and composite liners, infiltration rates through liners were also calcula ted based on the frequency and size of defec ts in the GM liner. The following obs ervations resulte d from this analy sis:

C The leak densities range from 0 to 774 leaks pe r hectare, with a mean of 43 leaks per hectare.

C A limited amount of data was collected on the sizes of leaks. L eak sizes range from pinholes t o a 30-cm seam def ect.

C A method f

or calc ulating leakag e rates

through defect s in GM and

composite

liners is presented for a GM alone , a GM com posi te li ner, an d a GM o verlai n by drain age material. Leakage rates were calculated f or these three liners for two hole sizes. The actual le akage

rates a re compa red to the calcula ted leak age ra tes for the GM over

lain with drainage materi al, since

nearly all of the GM liners

in the dat

abase ha ve a L CRS composed of sand or a sand/gravel c ombination. The actual leakage rate s are on the lower end of the range calcula

ted for the smaller hole size.
4.2 Geosynthetic Clay Liners
For GCL liners, only

a single document

on infiltr ation thro ugh a GC L wa s found. T

he hy draulic conductivity of the GCL

over a 9-week period was 2 x 10 -6 cm/s. The data pre sented in

this paper r eprese nts t he uni que en viron ment o f a sal init y-gradient solar pond ( which inclu des hi gh temperature, high salinity and low pH), which may not be representative of GCL use in other situations

. 4.3 Compacted Clay Liners
For CCL s, infiltration rates estimated using three methods, lysimeters, infiltrometer s, and water balance, were found in the literature. H owever, infiltration rates were only found for 9 sites. The average infiltration rates ra nge from 1.6 x 10 -9 cm/s to 1.2 x 10 -6 cm/s, with an average of 3.1 x 10 -7 cm/s. Due

to the limite d amount of

data ava ilable, these data

are not necessa

rily representative of infiltration rates through CCL s across the U.S. Hydraulic conducti vity data wa s also col lected f or CCL s. A data

base of f ield hy draulic conductivity values was c ompiled which contains 149 liners. The database can be summarized as follow s:

C The data mostly repr esent test pads (80 percent), with 7 percent in-ser vice WMUs and for the remainder, this information was not reported.

C There a

re 137 na tural cla y liners in the

databas e and 12 s oil/benton ite liners.

C Most of the

liner site s are loc ated in the Southea st and only a few sit es are i n the West. Only 56 perce

nt of sites report location data.

C Most of the liners were constructed with a formal CQA proc edure (69 percent); 5 perce nt were not and for the remainder, this information was not re ported.19

The infor mation on f

ield hy draulic conducti vities fr om the dat

abase is summarize d as follows:

C The field hydra

ulic conductivities for natural clay liners range from 1 x 10 -9 cm/s to 1 x 10 -4 cm/s, with an average of 6.5 x 10 -8 cm/s.

C The field hydra

ulic conductivities for soil/bentonite liners range from 2 x 10 -9 cm/s to 3 x 10 -6 cm/s, with an average of 3.3 x 10 -8 cm/s. These numbers only r epresent 12 liners, and cannot be consider ed repr esentat ive of soi l/bentonit

e liners i n gene ral.

C No t e no ug h d at a w as av ai la bl e t o c ha ra ct er iz e W MU s ( e. g. , l an df il ls , p on ds ) s ep ar at el y.

C Seventy perc ent of liner sites in the database have a field hy draulic conductivity value of less than or equal to 10 -7 cm/s, the common regulatory criterion.

C A comparison of field hy draulic conductivities to laboratory hydraulic conduc

tivities demonstr ates tha t labora tory tests ty pically under-predict f

ield values of hy

draulic conductivity. This concurs with obser vations reported in the literature.
4.4 Recom mendat

ions Based on the findings in this report, the following ar e recommended:

C For GM and composite liners, the ty pe of LDS drainag e material, the level of CQA performed, and the ty

pe of GM material have a potentially significant influence on L DS flow rates. Further investigation of the re lationship between these parameters and the LDS flow rates should be perfor med. If a signific ant relationship is determined, and sufficient data are available, diffe rent distributions could be created for different categories based on these par ameters. For example, a distribution could be created for HDPE liners with good CQA and a geonet dra inage sy stem.

C For GM/CCL liners, leakag e rates are difficult to determine beca use of the presence of consolidation water in the LDS sy stem. Several studies present methods for addressing this issue, though not for isol ating L DS flows du

e to leak age a lone. The se method s could be investigated further to determine if a distribution of leaka ge rates could be developed for GM/CCL

liners.

C For CCL s, not enou gh infor mation wa s availa

ble on inf iltration rates to a dequate ly develop a distribution. However, information on field hy draulic conductivities was plentiful. The relationship between the liner characteristics and construction information is potentia

lly r elated to the field hyd raulic c onductivi

ty values. If a distri

bution of f

ield hyd raulic c onductivi

ties is des ired, the

relation ship betwe en the conductivity and these parameters should be investigated. This could be done by creating scatter plots relating the condu ctivity to each p aramete

r individually , and using

regre ssion techniques, including multiple regression, to determine the significa nce of the relationship. Once the relation ships have

been determined , the cond uctivitie s can be c ategor

ized by the most signific ant para

meters, a nd distribu

tions of c onductivi

ties can be generated

for those categories. Some investigation into the relationship between hy draulic conductivity and the liner characteristics and construction data has been performed in EPA (1998).20

C The time-variabi lity of leaka ge rat es should b e investigated fur ther. I n this rep ort, average leaka

ge rat es are provided f

or GM and

composite

liners for two time p eriods, during o peration and post- closure ; signifi cantly less leak age is o bserved during the postclosure period. Several literature source s present time-variable infiltration rates (contained in Appendix B), which could be analy zed for a potential relationship. The current LDS flow database can also potentially pr ovide useful information related to a time-series analy sis, such as a distribution of landfill operating life. No information was found in the litera

ture on the time-va

riability of infiltr ation ra tes or hy draulic conductivities of CCLs. This is potentially importa nt, as the long-term performance of a CCL cannot be addressed without this information. 

### 5.0 References Albrecht, K.A. and K. Cartwright. 1989. I nfiltration and hydraulic c onductivity of a compacted earthen liner. Ground Water, vol. 27, no. 1, pp. 14-19. Benson, C.H. and D .E. Danie l. 1994. Min imum thickness of compacted soil liners: II . Analy

sis and case histories. Journal of Geotechnical Enginee ring, vol. 120, no. 1, January, pp. 153- 172. Benson, C.H., D.E. Daniel, and G.P. Boutwell. 1999. Field perf ormance of compacted clay liners. Journal of Geotechnical and Geoenvironmental Engineering, vol. 125, no. 5, pp.390-403. Bergstrom, W.R., P.D. Creamer, H. Petrusha, and C.H. Be nson. 1995. Field performance of a double liner test pad. Geoenvironment 2000: Characterization, Containment, Remediation, and Performance in Environmental Geotechnics. Geote chnical Special Publication No. 46, ASCE, New York. Bergstrom, W.R., M.J. Takacs, and M.A. Olson. 1993. Behavior of five ope rating landfill leak detection systems. Procee dings, Waste Tech '93, Marina Del Rey , California. Bonaparte, R. 1995. Long -term performance of landfills. Geoenvironme nt 2000: Characterization, Containment, Remediation, and Performance in Environmental Geotec hnics. Geotechnical Special Publication No. 46, ASCE, New York. Bonaparte, R. and B.A. Gross. 1990. Field be havior of double-liner sy stems. Waste Containment Systems: Construction, Regulation, and Performa nce, Geotechnical Special Publication No. 26, ASCE, New York. Bonaparte, R. and B.A. Gross. 1993. L DCRS Flow from Double Lined L andfills and Surface Impoundments. EPA/600/R-93/070. NTIS Publication PB93-179885. Risk Reduction Engineering L aboratory , Office of Research and De velopment, U.S. EPA, Cincinnati, OH. Bonaparte, R., J.P. Giroud, and B.A. Gross. 1989. Rates of leakag e through landfill liners.21

Geosynthetics 1989 Confer ence, San Diego, California. Cartwright, K. and I .G. Krapac. 1990. Construction and performance of a long-term earthen liner experiment. Waste Containment Systems: Construction, Regulation, and Performanc e, Geotechnical Special Publication No. 26, ASCE, New York. Daniel, D.E. 1984. Predicting hy draulic conductivity of c lay liners. Journal of Geotec hnical Engineering, vol. 110, no. 2, pp. 285-300. Daniel, D.E. 1989. In-situ hy draulic conductivity tests for c ompacted clay s. Journal of Geotechnical Engineering , vol. 115, no. 9, September, pp. 1205-1226. Darilek, G.T., D.L. Laine and J.O. Parra. 1989. The electrical leak loca tion method for geomembrane liners: development and applica tions. Proceedings of the Geosy nthetics '89 Conference, San Diego, pp. 456-466. Day, S.R. and D.E. Da

niel. 1985. Hydraulic c onductivity of two prototy pe clay liners. Journal of Geotechnical Engineering , vol. 111, no. 8, pp. 957-970. Eith, A.W. and G.R. Koerner. 1997. Assessment of HDPE geomembrane performance in a municipal waste landfill double liner system a fter eight y

ears of service. Geotextiles and Geomembranes, vol. 15, pp. 277-287. Elsbury, B.R., D.E. Da

niel, G.A. Sraders, and D.C. Anderson. 1990. L essons learned from compacted clay

liner. Journal of Geotechnical Engineering , vol. 116, no. 11, pp. 1641-1660. Feeney , M.T. and A.E. Maxson. 1993. Field performance of double-liner sy stems in landfills. Geosy nthetics ‘ 93 Confer

ence Pro ceeding s. Industrial F abrics A ssociation Inte rnationa l, St. Paul, MN.
Giardino , V.G. an

d J.L. G uglielme tti. 1997. L

ong-te rm perfo rmance of a haza rdous wa ste landfill. Geotextiles and Geomembranes, vol. 15, pp. 255-267. Giroud, J.P., K. Badu-Tweneboah, and R. Bonaparte. 1992. Rate of leakage through a composite liner due to geomembrane defe cts". Geotextiles and Geomembranes, vol. 11, pp. 1-28. Giroud, J.P. and R. Bonaparte . 1989a. L eakag e throug

h liners c onstruct

ed with geomembranes-Part I . Geomembrane liners. Geotextiles and Geomembranes, vol. 8, pp. 27-67. Giroud, J.P. and R. Bonaparte . 1989b. Leakag e throug h liners c onstruct

ed with geomembranes-Part I

I. Composite liners. Geotextiles and Geomembranes, vol. 8, pp. 71-111.22

Gordon, M.E., P.M. Huebner, and P. Kmet. 1984. An evaluation of the performa nce of four clay-lined landf

ills in Wisconsin. Seventh Annual Madison Waste Conference: Municipal and Industrial Waste, September 11-12, 1984, pp. 399-460. University of Wisconsin. Gordon, M .E., P.M. H

uebner, and T.J. Mia

zga. 198 9. Hy

draulic conducti vity of three landfill clay liners. Journal of Geote chnical Engineering, vol. 115, no. 8, pp. 1148-1160.
Gross , B.A., R. Bon aparte , and J .P. G iroud . 1990 . Eval uatio n of fl ow fro m land fill leakage detectio n lay ers. I nternat ional Conf

erence on Geotextiles, Geomembranes, and Re lated Pro ducts, The Hag ue, Netherlands

. Hartley, Rober

t P. 1992. Surface Impoundments, Design, Construction, and Operation. Noye s Da ta Co rp or at io n, Pa rk Ri dg e, Ne w J er se y. Huebner, P.M., and M.E. Gordon. 1995. Estimating contaminant breakthroug h for a clay-lined municipa l solid waste landf

ill. Geoe nvironme nt 2000: Cha

racter ization, Con

tainment, Remediation, and Performance in Environmental Geotechnics. Ge otechnical Special Publication No. 46, ASCE, New York. Johnson, G.W., W.S. Crumley, and G.P. Boutwell. 1990. Field verification of clay liner hydraulic conduc

tivity. Waste Containment Sy stems: Construction, Regulation, and Performance, Geotechnical Special Publication No. 26, ASCE, New York. King, K .S., R.M. Qu

igley, F. Fer

nandez, D .W. Reade s, and A. B acopoulo s. 1993. Hy draulic conductivity and diffusion monitoring of the Keele Valley

Landfill liner, Maple, Ontario. Canadian Geotechnical Journal, vol. 30, no. 1, pp. 124-134. Laine, D.L . 1991. Analysis of pinhole seam lea ks located in geomembrane liners using the electrical leak location method: Case histories. Proceeding s, Geosynthetics ' 91, IFAI , Atlanta, pp. 239-253. Laine, D.L . and M.P. Miklas. 1989. Detection and location of leaks in geomembrane liners using an electrical method: Case histories. Superfund ' 89, Proceedings of the 10th National Conference, pp. 35-40. Laine, D.L . and G.T. Darilek. 1993. Loca ting leaks in geomembrane liners of landf ills covered with a protective soil. Geosynthe tics 93 Conference Proceedings. I ndustrial Fabrics Association International, St. Paul, MN. Lichtwardt, M.A. and A.I . Comer. 1997. Geosynthetics in a sa linity-gra dient solar pond environment. Geosynthe tics ‘97 Conference Proceedings. I ndustrial Fabrics Association International, St. Paul, MN.23

Luettich, S.M., R. Bonaparte, B .A. Coleman, and H.M. Tomlinson. 1995. Preconstruction testing of two soil

liner mat erials. G eoenvir

onment 200 0: Charac

terization, Contain

ment, Remediation, and Performance in Environmental Geotechnics. Ge otechnical Special Publication No. 46, ASCE, New York. Maule, J., R.K. Lowe, and J.L. McCulloch. 1993. Perfor mance evaluation of sy

nthetically lined landfills. Tappi Journal, vol. 76, no. 12, pp.172-176. McQuade, S.J. and A.D. Needham. 1999. Geomembrane liner de fects-causes, frequency , and avoidanc e. Proce edings o f the I nstitution o f Civil Engineers, Geotechnical En gineer ing, vol. 137, no. 4, pp. 203-213. Mosley, N.G. and F . Crozier. 1995. Application of a geomembrane leak loca tion survey at a UK waste disposal facility. Eng ineering Geology

of Waste Disposal, Geological Society Engineering Geology Special Publication No. 11, pp. 9-14. O'Sadnick, D.L., B .E. Simpson, and G.K. Kasel. 1995. Evaluation and performance of a sand/bentonite liner. Geoenvironment 2000: Characterization, Containment, Remediation, and Performance in Environmental Geotechnics. Geote chnical Special Publication No. 46, ASCE, New York. Othman, M. A., R. Bon

aparte , and B.A . Gross. 1 997. Preli minary results of composite

liner fie ld performance study . Geotextiles and Geomembranes, vol. 15, nos. 4-6, pp. 289-312. Peggs, I .D. 1993. Practical geoelectric lea k surveys with hand-he ld, remote, and water lance probes. Proceedings of Geosy nthetics '93, vol. 3, IFAI , Vancouver, pp. 1523-1532. Phaneuf, R.J. No Date. A state's perspective on CQA/CQC in environmental containment system d esign & c onst ructi on. Ne w York Stat e Depar tment of Env ironm ental Cons ervati on's Division of Solid Waste, Albany, NY. Reades, D.W., L.R. L ahti, R.M. Quigley, a nd A. Bacopoulos. 1990. Detailed case history of clay liner performance. Waste Containment Systems: Construction, Regulation, and Performance, Geotechnical Special Publication No. 26, ASCE, New York. Reddi, V.J. and P.D. Scarlatos. 1996. Leachate lea kage from landfills with modern liner systems. Water Resources B ulletin, vol. 32, no. 4, pp. 697-709. Rogowski, A.S. 1985. Effectiveness of a compacted c lay liner in preve nting ground water contamination. Proceedings of the Fifth National Sy mposium and Exposition on Aquifer Restoration and Ground Water Monitoring May 21-24, 1985, Columbus, Ohio, pp. 412-429. Rollin, A.L., M. Marcotte, T. Jacquelin, and L . Chaput. 1999. Leak location in exposed24

geomembrane liners using an e lectrical leak detection technique. Geosy nthetics ‘99 Specifying Geosynthetics and D eveloping Design Details, vol. 2, pp. 615-626. Sai, J.O. and D.C. Anderson. 1990. Field hydra ulic conductivity tests for compac ted soil liners. Geotechnical Testing Journal, GTJODJ, vol. 13, no. 3, September, pp. 215-225. Tedder, R.B. 1997. Evaluating the perfor mance of florida double-lined landfills. Geosy nthetics ‘97 Conference Proceedings, I FAI, St. Paul, Minnesota, pp. 425-438. Trast, J.M. and C.H. Benson. 1995. Estimating field hy draulic conductivity of c ompacted clay

. Journal of Geotechnical Engineering, vol. 121, no. 10, pp. 736- 739.
Trautwe in, S.J. and C. E. Williams. 1990. Per formanc e evalua

tion of ea rthen line rs. Waste Containment Systems: Construction, Regulation, and Performanc e, Geotechnical Special Publication No. 26, ASCE, New York. U.S. EPA. 1992. Action Leakag e Rates for Leak D etection Systems. Supplemental Bac kground Documen t for the F inal Doub le Liners and L eak Det ection Sy stems Rule

for Haza rdous Wast

e Landfills, Waste Piles, and Surface I mpoundments. EPA/530-R-92-004. NTIS Publication PB 92 -1 28 21 4. Of

fi ce of So li d W as te , W as hi ng to n, D. C. Ja nu ar y. U.S. EPA. 1996. Report of 1995 Workshop on Geosynthetic Clay Liners. EPA/600/R-96/149. Office of Resea rch and D evelopme

nt, Washing

ton, D.C.
U.S. EPA. 1 998. Asse ssment and Recomme ndations f or Optima

l Perfor mance of Waste Containment Systems. Office of Rese arch and Development, National Risk Manage ment Researc h Lab oratory

, Cincinat ti, Ohio. Draft Fi

nal. U.S. EPA. 1999a. Guide for Industrial Waste Management. EPA/530-R-99-001. Office of Solid Waste a

nd Emerg ency

Response , Washing

ton, D.C. U.S. EPA. 1999b. Technical Background Doc ument: Industrial Waste Manageme nt Evaluation Model (IWEM), Ground Water Model to Support the Guide for I ndustrial Waste Management. EPA530-R-99-002.
U.S. EPA. 1999c. User’s Guide for the I ndustrial Waste Management Evaluation Model (IWEM): Tier 1 L ook-Up Tables and Tier 2 Neural Networks. EPA530- R-99-003. Wilson-Fahmy, R.F. and R.M. Koer ner. 1995. Leakage rates through holes in geomembra nes overly ing ge osy nthetic c lay

liners. G eosy

nthetics 9 5 Confer

ence Pro ceeding s, IFAI, St . Paul, Minnesota, pp. 655-668. Workman, J.P. 1993. I

nterpre tation of l eakag e rates

in double- liner sy

stems. Pro ceeding s, 7th25

Geosynthetic Resea

rch Institute Seminar, Drexel University , Philadelphia, Pennsylvania, pp. 95-112.26

Figure 3.1-1. Di stributio n of LDS Flow D ata by Ge omembrane Material and Lin er Type for Geomembrane and Com posite Liners.

Figure 3.1-2. Distribution of LDS Flow Data by Liner Type and LDS Type for Geom embra ne and Composite Line rs.27

Figure 3.1-3. Distribution of LDS Flow Data by Type of Waste and Region for Geom embra ne and Composite Line rs.

Figure 3.1-4. Di stributio n of Waste Placem ent Start Dates for

Geom embra ne and Composi te Liners
.28

Figure 3.1-5. Distribution of LDS Flow Data by CQA Procedure and Liner Type for Geom embra ne and Composite Line rs.

Figure 3.1-6 Cumulative Distribution Functions of Average Monthly LDS Flows by Liner Type for G eomem

brane and Co mposite

Liners.29

Figure 3.1-7. Cumulative Di stributio n Functio ns of LDS Flow Measure ment P eriod by Liner Type fo r Geom embra ne and Composite Line rs.

Figure 3.1-8. Cumulative Di stributio n Functio n of Leak Dens ities for Geomem brane Liners.30

Figure 3.3-1. Num

ber of Com

pacted Cl ay Liner Sites by U.S. R egion.

Figure 3.3-2. Cumulative Distribution Function of Field Hydraulic Conductivity Values for All Com

pacted Cl ay Liners.31

Figure 3.3-3. Scatter Plot of Field Versus Laboratory Hydraulic Conductivity Values for Compacted Clay Liners.32

Table 2.1-1. List of Databases Used in Literature Survey

. Name Hosted By Web Add ress Years Covered Summary
EI Compendex Enginee ring Informati on, Inc. http://www.ei.org 1970-pre sent A bibliographic data base containing over 5 million records

and ref erences to more than 5,00 0 engin eering journals and conferences. National Technical Informati on Servi ce (NTIS) U.S. Department of Commer

ce http://www.nt is.gov 1990-pre sent (searcha ble); older documents available Larges t, centra l resour

ce for go vernmen t-funded scie ntific, technical, engineering, and b usiness related information with over 2 million publications cove ring over 350 subject a reas.

DIALOG A Thomson Company http://www.d ialog.com 1964-pre sent Database of abs tracts from Pollution Abstracts, Environme ntal Bi bliogra phy, JIC ST-EPlus - Japanese Science & Technology, PASCAL sciBASE The Scientific World http://thescienti ficworld.co m 1993-pre sent Databa se of s cientifi c, technica l and m edical resea rch literature, including app roximately 12 million articles publis hed si nce 1993 in more t han 20,000 journals

. California Digital Librar y (Melv yl and Periodicals database) Univers ity of California http://www.cdlib.org Variable Melvyl contains records for mat erials (books, archives, audio-visuals, computer files, videorecordings, dis sertations, government documents, maps, mus ic scores, and recordings) in the libraries of the nine UC campuses, California State Library, California Academy of Sciences, California Historical Society, Center for Research Lib raries, and the Gra duate Theological Union. The Periodicals Database allows us ers to search the titles of serials (periodicals , newspapers, annuals, some monographic series, a nd other ongoing publications) owned by

more tha n 550 Cal ifornia l ibrari es. Nationa l Servi ce Center for Environmental Publications (NSCEP) U.S. Environmental Protecti on Agency http://www.e pa.gov/ ncepihom Unknown The NSCEP maintains and distributes EPA p ublications in hardcopy

, CD ROM a nd other

multi-m edia f

ormats. The current publication inventory includes over 7,000 titles.

Table 2.1- 1 continue d.33

Name Hosted By Web Add ress Years Covered Summary

National Environmental Publica tions International Site (NEPIS) U.S. Environmental Protecti on Agency http://www.e pa.gov/ ncepihom

/nepishom/ Unknown The NEPIS contains over 6,000 full tex t, on line EPA documents.

EPA Offi ce of Res

earch and Dev elopme nt (ORD) U.S. Environmental Protecti on Agency http://www.e pa.gov/ORD/

publica tions Variable Collecti on of pub lication s by t he ORD

Web of Sci ence Institut e for Scientific Informati on (ISI) http://www.we bofscie nce.com 1945-pre sent Web of Science consists of three databases: Arts &

Humanities Citation Index, Social Sciences Citation Index, and Science Citation Index E xpanded. Web of Science cove rs thousand s of res

earch jo urnals across h undreds of disciplines. Access restricted to subscribers only. Science D irect N/A http://www.s cienced irect.com Unknown ScienceDi rect is an ele ctronic in formation servi ce offeri ng comprehe nsive coverag e of lit erature across all fie lds of science , includi ng over

1.2 mill ion full-text a rticles and 30 million abstracts. Access restricted to subscribers only.34

Table 3.1-1. Typical Defects of Geomembrane Liners and Possible Causes

. Stage Type of Defect Possibl e Cause/Comment Ma nufactu re Pinholes, excessive t hickness change s, poor stress crack resistance Unus ual now for proce dure s with g ood q uality contr ol. Poor r esin.
Delivery Scuffi ng, cuts, brit tle cr acks, tear s, punc tur es Unloadi ng with u nsui table plantor l if ti ng equi pment. Impact . Po orl y pr epared sto rage areas. Placement Scratches, cuts, holes, t ears, cri mps Dragging s heet al ong ground, tri mm ing of panels, rough s ubgrade, use of equipment on top of sheet wi thoutprotec ti on lay er, wi nd damage, large wrinkl es, f olds, damage by li fti ng bars. Welding Cuts , ov erheat ing , s cor ing , poor adhesi on, c ri mping Careles s edge tr imming, weldi ng speed or tem pera ture incorre ct, excess ive grinding , dirt, or damp i n weld area, exces si ve r oll er pr essu re. Cover Pl acement Tears, cuts and scratches, holes, str ess i n mem brane Acti on of eart hmovin g pl ant, in suf fi ci ent c over duri ng pl acement, car eles s pr obi ng of cov er depth. Contrac ti on of s heet due t o ambient temperature reduct ion. Post- Inst all ati on Holes, teari ng, sli ts, c racks Punct ure f rom drai nage mater ial s, punc tur e by it ems of deposi ted wast e, o peni ng of part ial depth cuts, pul li ng apart of poor quali ty welds, downdrag str esses caus ed by s ett li ng wast e, diff erential settl emen t in t he base

. Source: McQu ade an d Need ham (1999 ).
Table 3.1-2. LDS Flow Database for Landfill Cells with Geomembrane or Composite Liners. (Table p rovided i n MS Excel)35

Table 3.1-3. Per cent of Sit es Repor ting Par amete rs by Liner Type for G eomem

brane and Composi te Liners
. Parameter Percent of Sites Reporting Parameter by Liner Type GM GM/CCL GM/GCL GM/GCL /CCL GM/GCL

/GM All
Total Numb

er of Cells 87 140 27 3 2 259 Average Monthly LDS Flow Rate 97 98 100 100 100 98 Minimum Monthly LDS Flow Rate 34 39 7 0 0 33 Maximum Monthly LDS Flow Rate 97 99 96 100 100 98
Period of Measurement 100 99 100 100 100 100 Length of Initial Operating Period 68 65 93 100 100 69 Type of Waste 83 65 93 100 100 75 Location 100 66 100 100 100 82 Average A nnual Rain fall 69 61 89 100 100 68 Depth to Groundwat er 38 56 89 67 100 54 Subsurface Soil Type 9 21 78 100 100 25 Cell Area 100 64 100 100 100 81 GM Liner Mat

erial 98 100 100 100 100 99 GM Liner Thick

ness 98 99 100 100 100 98 GCL/CCL Thickness

- 100 100 100 100 100 Maximum Height of Waste 31 52 85 100 100 49 LCRS Materi al 100 100 100 100 100 100 Average Liner Base Slope 86 59 96 100 100 73 End Construction Date 98 100 100 100 100 99 Waste Placement Start Date 70 100 93 100 100 89 Final Closure Date 66 66 89 100 100 69 Assessment of CQA Proced ures 92 96 100 100 100 95 LDS Flow Measurement Method 36 37 81 33 0 41 LDS Pipe or Swale Size and Material 39 46 70 100 0 47 LDS Pipe or Swale Spacing 33 23 70 100 100 33 Material of Drainage Lay er 100 100 100 100 100 100 Thickness of Drainage Lay er 79 63 93 100 100 72 Note: - = no

t applicab le.36

Table 3.1-4. LDS Flow Database for Landfills with Geomembrane or Composite Liners During the

Post-C losure P eriod. (Table p rovided i n MS Excel) Table 3.1-5. Statistics of Average Monthly LDS Flow Rates by Liner Type for Geom embra ne and Composite Line rs. LinerType Num ber of Sit es Rep orting Da ta Average Monthl y LDS Flow (l phd)
Mean Median Minimum Maximum
GM 84 258 65 1 4282 GM/CCL 131 130 84 0 1410 GM/GCL 24 4 0 0 32 GM/GCL/CCL 3 250 167 92 492 GM/GCL /GM 2 52 52 12 92 Table 3.1-6. Statistics of Average Monthly LDS Flow Rates by CQA Procedure for Geom embra ne and Composite Line rs.

LinerType Param eter Average Monthl y LDS Flow (l phd) All C ells Cells Constructed

wit h Goo d CQA Cells Constructed with No For mal CQA GM Num ber 84 71 9

Mean 258 246 423 Median 65 53 108 Minimum 1 1 20 Maximum 4282 4282 1603 GM/CCL Num ber 131 117 11

Mean 130 133 64 Median 84 90 53 Minimum 0 0 9 Maximum 1410 1410 14837

Table 3.1- 7. Statist

ics of LDS F low Measur ement Perio d by Liner Type

for Geom embra ne and Compo site Liner s. LinerType Num ber of Sit es Rep orting Da ta Flow Measurem ent Period ( months)
Mean Median Minimum Maximum
GM 84 27 26 2 79 GM/CCL 131 33 29 3 92 GM/GCL 24 36 36 6 69 GM/GCL/CCL 3 11 5 4 25 GM/GCL /GM 2 19 19 10 28 Table 3.1-8. Statistics of Average Monthly LDS Flow Rates During the Post-Closure Perio d for Landfills with Geom embra ne or Com posite Line rs. LinerType Num ber of Sit es Rep orting Da ta Average Monthl y LDS Flow (l phd)
Mean Median Minimum Maximum
GM 8 64 24 1 210 GM/CCL 22 69 51 0 274 GM/GCL 6 10 0.5 0 59
Table 3.1- 9. Leak De nsity Data for Geom embra ne Liners. (Table p rovided i n MS Excel) Table 3.1-10. Leak Density Statistics by Potentially Significant Parameter for Geom embra ne Liners. Param eter Number of Sites W ith Da ta Leak Dens it y (l eaks/h a)
Mean Median Minimum Maximum
For mal CQA Program Followed 26 2.03 0.92 0 12.5
HDPE Liner Type 120 6.5 1.0 0 120 All C ells 247 43 8.2 0 77438

Table 3.1- 11. Leak De nsity Data for Soil-Covered Geomem brane Liner s. Lea k D ens ity (Leaks /Ha) Number of Sites 0 1 1.08 1 3.23 2 3.7 1 4.63 3 5.49 3 7.21 1 10.44 2 20 1 26.69 2 39.83 1 143.48 1
Table 3.1- 12. Range s of Leak Size s found in Liter ature for Geom embra ne Liners. Reference Holes Knife C uts/T ears Seams/W elds Notes Roll in et al. 1995 < 2 mm 2 : 25%

2- 10 mm 2 : 50% > 1 0 mm 2 : 25% 2- 10 mm 2 : 40% > 1 0 mm 2 : 60% < 2 mm 2 : 66% 2- 10 mm 2 : 26% > 1 0 mm 2 : 8% McQuade and Needham 1999 rang e pinho le to 50 00 mm range 20 mm x 50 mm to 30 mm x 50 mm NA See Table 3.1-9 for s ite-s pe cific ranges Lai ne and Mi kl as 1989 rang e <0 .025 in to 1 in range 0. 25 in to 12 in NA Only rang es reported Laine 1991 0.0 4 i n di ameter 0.04 in cut; 0.0 2 in x 0.00 6 in fl aw 0.0 4 i n di ameter Sizes not rep orte d fo r all defects Mosley and Crozi er 1995 NA 2 cm cut; 15 cm cut NA Sizes not rep orte d fo r all defects Peggs 1993 None None 30 cm Only o ne w aste cel l r eport ed39

Table 3.1- 13. Equations Represe nting Leakag e Rates Through Hole s for Geo membrane and Compo site Liner s.

Geomembrane Alone Composite Liner Geomembrane Overlain by Drainage Material Good con tact Poor cont act Equation

Definitions Q = steady-s tate ra te of le

akage through one hole

(m 3 /s) a = area of hole

in the geomemb rane (m 2 ) C B = dimen sionles

s coeffic ient, for

sharp edges

= 0.6 g = accel eration of grav ity (9.81 m/s 2 ) h = head of liquid on top of geomembrane (m) k s = hydraulic conductivity of the low-pe rmeability soil unde rlying the geomembra ne (m/s) k d = hydraulic conductivity of draina ge material overl ying the geomembra ne (m/s)

Limitations Equation can be used

if soil underly ing geomembrane has conductivity greater than 10 -3 m/s when geomembrane hole area i s 0.1 cm 2 , and a conductivity greater than 10 -2 m/s when geomembrane hole area i s 1 cm 2

. Equatio n for sit uations where cond uctivity

of low-permeability soil is less t han 10 -6 m/s and the hea d of liq uid on top of th e geomembrane is le

ss than the thickness of the low-permeability soil la yer. Good contact corresponds to geomemb rane installed with as few wrinkles as pos sible on top of low-permeability soil layer that has been adequate ly compacted and has a smooth surface. Equatio n for sit uations where cond uctivity

of low-permeability soil is less t han 10 -6 m/s and the hea d of liq uid on top of th e geomembrane is le

ss than the thickness of the low-permeability soil la yer. P

oor contact corresponds to a geomembrane that has been i nstalle

d with a certain number o

f wrinkles, and/or placed on a low-permeability soil that has not be

en well compacted a nd does not appear smooth. Hydraulic conductiv ity of drainage material greate r than 10 -6 m/s. Head of liquid on top of geomembrane less than thi ckness

of drainage layer.

Source: Bon aparte

et al. (1989).40

Table 3.1-14. Calculated Leakage Rates (lphd) for Geomembrane and Com posite Liners Assu ming H ole S ize of

3.1 mm 2
. De pt h o f Li qu i d ( m) 0.001 0.01 0.1 0.3 Geomem brane alone 970 (Mean) 190 (Medi an) 3060 (Mean) 590 (Medi an) 9700 ( Mean) 1900 ( Median) 16800 ( Mean) 3200 (Median) Composite Liner with Good Contact 0.096 (Mean) 0.02 (Median) 0.76 (Mean) 0.2 (Median) 6.0 (Mean) 1.2 (Median) 16 (Mean) 3.1 (Median)
Composite Liner with Poor Contact 0.5 (Mean) 0.1 (Median) 4.2 (Mean) 0.8 (Median) 33 (Mean) 6.4 (Median) 89 (Mean) 17 (Medi an)

Geomem brane Ov erlain with Drainage Mater ial 46 (Mean) 9 (Medi an) 260 (Mean) 50 ( Median) 1500 ( Mean) 280 ( Median) 3300 ( Mean) 640 ( Median)

Table 3.1-15. Calculated Leakage Rates (lphd) for Geomembrane and Com posite Liners Assuming Hole Size of 1 cm 2
. De pt h o f Li qu i d ( m) 0.001 0.01 0.1 0.3 Geomem brane alone 31000 ( Mean) 6000 ( Median) 99000 ( Mean) 19000 ( Median) 312000 ( Mean) 60000 ( Median) 540000 ( Mean) 104000 ( Median) Composite Liner with Good Contact 0.14 (Mean) 0.03 (Median) 1.1 (Mean) 0.21 (Median) 8.6 (Mean) 1.7 (Median) 23 (Mean) 4.4 (Median)
Composite Liner with Poor Contact 0.7 (Mean) 0.1 (Median) 6.0 (Mean) 1.1 (Median) 47 (Mean) 9.0 (Median) 130 (Mean) 24 ( Median)

Geomem brane Ov erlain with Drainage Mater ial 630 (Mean) 120 (Medi an) 3500 (Mean) 680 ( Median) 19800 ( Mean) 3800 ( Median) 45200 ( Mean) 8700 ( Median)41

Table 3.1-16. Calculated Leakage Rates (lphd) Through Holes in Geomembranes Overlying Geosynthetic Clay Liners

. Tra nsm issivity of GM-GCL Interf ace (m 2 /s) Hydraulic conducti vity of GCL (m/ s)

1 x 10 -12 1 x 10 -11 5 x 10 -11 1 x 10 -10

10 -12 7300 11,000 19,000 26,000 10 -11 54,000 74,000 103,00 0 122,00 0 10 -10 487,00 0 615,00 0 770,00 0 860,00 0 10 -9 4 x 10 6 4.3 x 10 6 5.1 x 10 6 5.6 x 10 6
10 -8 3.1 x 10 7 3.5 x 10 7 3.8 x 10 7 4 x 10 7 Note: Numbers are ap proximate since they were estimated from graphs. Source: Wil son-Fahm y and K oerner ( 1995). Table 3.1- 17. Comparison of Ac tual Ver sus Calcula

ted Leakag e Rates

for Geom embra ne Liners

. Actu al Le aka ge R ate (lphd) Calcul ated Leakage Rate (l phd) 3. 1 mm 2 ho le 1 cm 2 ho le Mean 258 46-3300 630-452 00 Median 65 9-640 120-870 0
Table 3.3- 1. Infiltrat

ion Data for

Compacted Clay Liners. (Table p rovided i n MS Excel)
Table 3.3- 2. Hydraulic

Conductivi

ty Data for

Compacted Clay Liners. (Table p rovided i n MS Excel)42

Table 3.3-3. Per cent of Sit es Repor ting Par amete rs for Com pacted Cl ay Liner Hy draulic Conductivi

ties. Param eter Percent of Sit es Reporting Parameter Waste Management Unit Type 38 In-Se rvi ce orTestPad 88 Measurement Method 100 Size of Test Apparatus 69 Locati on 56 Con struc tion D ate 7 Monitor ing Per iod 5 Liner Characteristics

Line r Mate ri al 100 Are a o f Ce ll 64 Liner Thickness 89 Liq uid Lim it 77 Plasti city I ndex 92 Percent Fines 67 Clay Fr acti on 44 Pe rcen t Ben tonite 75 Optimum Water Conte nt 70 Maximum D ry Uni t Weight 67 Com pactive E ffort 68 Constr ucti on Information

Compa ctor Mass 57 Pas ses pe r Lift 50 LiftThickness 72 Nu m ber o f Lifts 72 Fo rma l CQ A Pr og ra m? 74 Qua lity Assu rance / Qua lity Contro l Data Water cont ent 70 Dry De nsity 69 Po 61 Freq uen cy o f Mo isture De nsity Tes ts 2 Time Lapse Between Completion of Li ner and Filling W ith W ater/ W aste 1

La bora tory H ydra ulic Co ndu ctivity 7243

Table 3.3-4. Statistics of Field Hydraulic Conductivity by Liner Material for Compacted Clay Liner s. LinerType Number of Sites Report ing Da ta Fiel d Hydraulic Conducti vity ( cm/s)

Mean Median Minimum Maximum

Natur al Cl ay 137 6.5 x 10 -8 5.0 x 10 -8 1.0 x 10 -9 1.0 x 10 -4

Soil/Ben tonite 12 3.3 x 10 -8 2.6 x 10 -8 2.0 x 10 -9 3.0 x 10 -6

All 149 6.1 x 10 -8 4.5 x 10 -8 1.0 x 10 -9 1.0 x 10 -4

Table 3.3- 5. Statist

ics of Field Hydraulic

Conductivi

ty by Waste

Managem ent Unit Ty

pe for Compacted Cl ay Liners. LinerType Number of Sites Report ing Da ta Fiel d Hydraulic Conducti vity ( cm/s)

Mean Median Minimum Maximum

La nd fill 8 9.0 x 10 -9 8.0 x 10 -9 2.0 x 10 -9 4.4 x 10 -8

Pond 3 1.1 x 10 -5 1.5 x 10 -5 3.0 x 10 -6 3.2 x 10 -5

TestPad 120 6.2 x 10 -8 4.8 x 10 -8 1.0 x 10 -9 1.0 x 10 -4

All 149 6.1 x 10 -8 4.5 x 10 -8 1.0 x 10 -9 1.0 x 10 -4