Characterization of Infiltration Rate Data to Support Groundwater

Modeling Efforts

Draft

Prepared for:

U.S. Environmental Protection Agency

Office of Solid Waste and Emergency Response

CONTRACT NO. 68-W6-0061

Work Assignment No. 3-59

Prepared by:

Tetra Tech, Inc. 

3746 Mt. Diablo Blvd., Suite 300

Lafayette, CA 94549

May 31, 2001
i

TABLE OF CONTENTS

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 Leak Detection System Flow Data 5

3.1.2.1 Analysis of Scope of Data 6

3.1.2.2 Analysis of LDS Flow Data 8

3.1.3 Calculated Leakage Rates 10

3.1.4 Comparison of Actual and Calculated Leakage Rates 12

3.2 Geosynthetic Clay Liners 12

3.2.1 Review of Literature 12

3.2.2 Performance Data 13

3.3 Compacted Clay Liners 13

3.3.1 Review of Literature 14

3.3.2 Infiltration Data 14

3.3.3 Hydraulic Conductivity Data 15

3.3.3.1 Analysis of Scope of Data 15

3.3.3.2 Analysis of Hydraulic Conductivity Data 16

4.0 Summary and Recommendations 17

4.1 Geomembrane and Composite Liners 17

4.2 Geosynthetic Clay Liners 18

4.3 Compacted Clay Liners 18

4.4 Recommendations 19

5.0 References 20

Appendix A Bibliography

Appendix B Copies of Documents Containing Time-Varying Infiltration Data for

Geomembrane and Composite Liners
ii

LIST OF FIGURES

Figure 3.1-1. Distribution of LDS Flow Data by Geomembrane Material and Liner Type for

Geomembrane and Composite Liners.

Figure 3.1-2. Distribution of LDS Flow Data by Liner Type and LDS Type for Geomembrane

and Composite Liners.

Figure 3.1-3. Distribution of LDS Flow Data by Type of Waste and Region for Geomembrane

and Composite Liners.

Figure 3.1-4. Distribution of Waste Placement Start Dates for Geomembrane and Composite

Liners.

Figure 3.1-5. Distribution of LDS Flow Data by CQA Procedure and Liner Type for

Geomembrane and Composite Liners.

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

for Geomembrane and Composite Liners.

Figure 3.1-7 Cumulative Distribution Functions of LDS Flow Measurement Period by Liner

Type for Geomembrane and Composite Liners.

Figure 3.1-8. Cumulative Distribution Function of Leak Densities for Geomembrane Liners.

Figure 3.3-1. Number of Compacted Clay Liner Sites by U.S. Region.

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

Compacted Clay Liners.

Figure 3.3-3. Scatter Plot of Field Versus Laboratory Hydraulic Conductivity Values for

Compacted Clay Liners.
iii

LIST OF TABLES

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

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

Table 3.1-2. LDS Flow Database for Landfill Cells with Geomembrane or Composite Liners.

Table 3.1-3. Percent of Sites Reporting Parameters by Liner Type for Geomembrane and 

Composite Liners.

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

the Post-Closure Period.

Table 3.1-5. Statistics of Average Monthly LDS Flow Rates by Liner Type for Geomembrane

and Composite Liners.

Table 3.1-6. Statistics of Average Monthly LDS Flow Rates by CQA Procedure for

Geomembrane and Composite Liners.

Table 3.1-7. Statistics of LDS Flow Measurement Period by Liner Type for Geomembrane and

Composite Liners.

Table 3.1-8. Statistics of Average Monthly LDS Flow Rates During the Post-Closure Period

for Landfills with Geomembrane or Composite Liners.

Table 3.1-9. Leak Density Data for Geomembrane Liners.

Table 3.1-10. Leak Density Statistics by Potentially Significant Parameter for Geomembrane

Liners. 

Table 3.1-11. Leak Density Data for Soil-Covered Geomembrane Liners.

Table 3.1-12. Ranges of Leak Sizes found in Literature for Geomembrane Liners. 

Table 3.1-13. Equations Representing Leakage Rates Through Holes for Geomembrane and

Composite Liners.

Table 3.1-14. Calculated Leakage Rates (lphd) for Geomembrane and Composite Liners

Assuming Hole Size of 3.1 mm2.

Table 3.1-15. Calculated Leakage Rates (lphd) for Geomembrane and Composite Liners

Assuming Hole Size of 1 cm2.

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

Geosynthetic Clay Liners.

Table 3.1-17. Comparison of Actual Versus Calculated Leakage Rates for Geomembrane

Liners.

Table 3.3-1. Infiltration Data for Compacted Clay Liners.

Table 3.3-2. Hydraulic Conductivity Data for Compacted Clay Liners.

Table 3.3-3. Percent of Sites Reporting Parameters for Compacted Clay Liner Hydraulic

Conductivities.

Table 3.3-4. Statistics of Field Hydraulic Conductivity by Liner Material for Compacted Clay

Liners.

Table 3.3-5. Statistics of Field Hydraulic Conductivity by Waste Management Unit Type for

Compacted Clay Liners.
iv

ABBREVIATIONS

Abbreviation Definition

ASH(M) Municipal ash

ASH(C) Coal ash

CCL Compacted clay liner

C&DW Construction and demolition waste

CSPE Chlorosulfonated polyethylene 

CQA Construction quality assurance

EPA U.S. Environmental Protection Agency

FML Flexible membrane liner

GCL Geosynthetic clay liner

GM Geomembrane

GN Geonet

GT Geotextile

ha Hectare

HDPE High density polyethylene

HW Hazardous waste

ISW Industrial solid waste

IWEM Industrial Waste Management Evaluation Model

LCRS Leachate collection and removal system

LDS Leak detection system

LLDPE Linear low density polyethylene

LMDPE Linear medium density polyethylene

lphd Liters per hectare per day (1 lphd = 9.35 gallons/acre/day [gpad] =

1.16 x 10-10 cm/s)

MSW Municipal solid waste

PS Paper sludge

PVC Polyvinyl chloride 

SDRI Sealed double-ring infiltrometer

TC Tire chips
1

1.0 Introduction

In May 1999, the U.S. Environmental Protection Agency (EPA) completed the Industrial D Tier

1 and Tier 2 groundwater tools to assist regulators, industry, and the public in evaluating the

design of Industrial D waste landfills, surface impoundments, land application units, and waste

piles. These tools are described in the document Guide for Industrial Waste Management (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 and Tier 2 tools was completed

and the tools were released for public comment. Peer reviewers of the tools expressed concern

that the methodology EPA used to establish the rates of leachate infiltration through lined waste

management units (WMUs) did not consider expected variability in liner performance. EPA is in

the process of revising the Tier 1 and Tier 2 tools and is considering incorporating distributions

of infiltration rates for single- and composite-lined units into the tools (some variability due to

climate conditions is already incorporated into EPA’s infiltration rate assumptions for single,

clay-lined units).

In order to characterize 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 systems (specifically, the rates

of leachate infiltration through liners); and 2) describe 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 describe the performance of liners

“as installed” or “as operated.” The liner types considered are the following:

C Single liners, including compacted clay liners (CCLs), geomembrane (GM) or flexible

membrane liners (FMLs), and geosynthetic clay liners (GCLs)

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

geosynthetic clay liner

C Double liners, which include two distinct liners, a primary (top) and secondary (bottom)

liner, each of which are one of the types described above.

Further description of these liner types can be found in the Guide for Industrial Waste

Management (EPA 1999a).

This memorandum summarizes the investigation of infiltration rates through liners. In Section 2,

the literature survey and results are described. Section 3 presents the infiltration rates and other

relevant data acquired through the literature for the different liner types. A summary and

recommendations based on the infiltration data acquired are presented in Section 4.
2

2.0 Literature Survey

2.1 Process

A literature survey was designed to identify and retrieve documents containing information on

the performance of liners of landfills, surface impoundments, and waste piles. Specifically,

documents on infiltration rates through liners were targeted, though documents were collected if

they contained other information related to the performance of liners.

Data sources included the scientific literature, EPA reports, and reports from other

government and university sources. Electronic searches were conducted using the databases

shown in Table 2.1-1.

Additionally, the websites of the following organizations were visited and searched for relevant

information:

C International Geosynthetics Society (http://igs.rmc.ca/igs/index.html)

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

C Geosynthetica (http://geosynthetica.net)

C Tappi (http://www.tappi.org)

A number of key words and word combinations were used in the search to identify relevant

literature:

C liner(s) and performance

C waste management unit and performance 

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 geosynthetic and liner(s)

C geosynthetic and leak

C geosynthetic and performance

Additionally, once documents were obtained, the reference lists from those documents were

reviewed for potential additional sources.

2.2 Results

A total of 132 documents were obtained and reviewed 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 literature survey. Eighteen documents were found

containing data on leak detection system (LDS) flow rates of double-lined landfills with a GM or
3

composite primary liner. These are used to estimate leakage rates through such liners. Fourteen

documents were found that contain information on calculated leakage rates through holes and

defects in geomembrane liners, including hole/defect frequencies for landfills. One document

was found containing infiltration rates through a GCL. For CCLs, 9 documents were found

estimating infiltration rates through the liners using methods such as lysimeters, infiltrometers,

and water balance. An additional 19 documents were found containing information on hydraulic

conductivity of compacted clay liners. Finally, five documents were found that contain

information on the general performance evaluation of landfills or surface impoundments. These

documents generally contained site and liner descriptions, and a description of the performance

(and failure mechanism, if applicable), but no specific infiltration data.

While gathering the literature, emphasis was placed on finding 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 compacted

clay liners at actual sites, literature was also collected on test plots. Most of the information in

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 Data

This section presents the infiltration rates and other potentially relevant data collected from the

literature, and is organized by liner type. No information was found on infiltration through

double-lined landfills, therefore, this liner type is not included.

3.1 Geomembrane and Composite Liners

GMs (or FMLs) are used to contain or prevent waste constituents and leachate from escaping a

WMU. GMs are made by combining one or more plastic polymers with ingredients such as

carbon black, pigments, fillers, plasticizers, processing aids, cross-linking chemicals,

anti-degradants, and biocides. A wide range of plastic resins are used for GMs, including

polyvinyl chloride (PVC), high density polyethylene (HDPE), linear medium density

polyethylene (LMDPE), and chlorosulfonated polyethylene (CSPE).

Leakage through GM liners can occur because of permeation and due to defects in the liner itself. 

Leakage from permeation is small compared to leakage from defects (Giroud and Bonaparte

1989a,b). There are three types of defects typically found in GM liners: pinholes, holes, and

seam defects. Pinholes have openings significantly smaller than the GM thickness and are

caused by manufacturing defects. Current manufacturing processes have resulted in pinholes

being relatively rare. Holes are openings that are the same size or larger than the thickness of the

GM. Seam defects are defective seams resulting from fabrication or installation factors or seam

failures caused by excessive stresses during cover placement or facility operation. Table 3.1-1
4

summarizes typical defects and their likely causes.

For GM and composite liners, one of the best ways of estimating leakage rates 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 (EPA 1998):

1. Construction water – water (mostly rainwater) that infiltrates the LDS 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 result of LDS

compression under the weight of the waste.

3. Consolidation water – water expelled into the LDS from any CCL and/or GCL

components of a composite primary liner as a result of clay consolidation under the

weight of the waste.

4. Infiltration water – water that percolates through the secondary liner and infiltrates the

LDS.

For all GM and composite liners contained in this report, infiltration water is not an issue unless

otherwise noted. All liners are either well above the water table or are constructed as to prevent

infiltration from groundwater into the LDS system.

For GM and GM/GCL liners, the only potential sources of water to the LDS are construction

water, compression water, and leakage through the primary liner. For cells with geonet LDSs,

the construction and compression water are not applicable since the geonet drains rapidly. For

cells with sand LDSs, construction and compression water may be significant sources of LDS

flows while the sand LDS drains (typically up to 1 year after cell construction). For GM/GCLs,

consolidation water is only a potential source if the GCL hydrates prior to waste filling, which 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 of Literature

In the literature review, two types of documents were collected in order to estimate leakage rates

through GM and composite liners: 

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 rates 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 report 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 (ISW) landfills. It includes data for the initial

period of operation, active period of operation, and post-closure period. Seven other separate

documents were found that use or summarize some of the same data that is contained in EPA

(1998). These include: Bonaparte (1995), Bonaparte and Gross (1990), Bonaparte and Gross

(1993), Gross et al. (1990), Othman et al. (1997), EPA (1992), and EPA (1996). In addition to

the EPA (1998) report, 9 other documents were found that contain LDS flow data: Bergstrom et

al. (1993), Eith & Koerner (1997), Feeney & Maxson (1993), Giardino & 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 leakage rates based on the frequency

and size of defects in the GM liner. Four documents (Giroud & Bonaparte 1989a,b; Bonaparte et

al. 1989, and Giroud et al. 1992) present methods for performing this calculation along with

some estimated leakage rates. Eight documents provided information on hole/defect frequencies

for landfills: Darilek et al. (1989), Laine (1991), Laine & Darilek (1993), Laine and Miklas

(1989), McQuade and Needham (1999), Mosley and Crozier (1995), Peggs (1993), and Rollin et

al. (1999). Two documents present leakage rates 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 Detection System Flow Data

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 were found

from the literature. Since the focus of this report is on infiltration rates during the WMU’s active

period of operation, when possible, only LDS flows during this period are reported in Table 3.1-

2. The active period of operation is defined as the period during which the cell is filled with

waste and daily and intermediate layers of cover 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 collection and
6

removal system (LCRS) flow rates stabilize. For other data sources, the active period of

operation may exclude time required for drainage of the sand LDS; these are noted in the Notes

column. For all other data sources, the active period of operation includes some or all of the time

of waste filling unless otherwise noted. The duration of the excluded period, 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 hectare per day (lphd), but no information on

specific landfills is reported. These double-lined landfills contain a primary composite liner

constructed under a comprehensive CQA program. Due to the lack of specific liner information,

this data is not included in Table 3.1-2.

The parameters represented in Table 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 parameter. Of the 26 identified parameters, 16

contained data for over 70 percent of the cells. For the most part, information about the cell and

liner (e.g., location, liner type and thickness, LDS type) was more likely to be reported than more

general site data (e.g., rainfall, depth to groundwater, subsurface soil type). Information on the

specifics of the LDS system (e.g., flow measurement method) was also lacking. The types of

data reported were similar across all liner types, except the GM/GCL liner, which tended to have

more data reported. This is due to the fact that most of the GM/GCL cells are from the same data

source.

It should be noted that some documents contained time-variable infiltration during the

operational period. Since the Industrial Waste Management Evaluation Model (IWEM) (EPA

1999b,c) for which these data are intended, 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 address the time-variability issue, a limited amount of data on average monthly

LDS flow rates for landfills during the post-closure period was compiled from the same sources

as the LDS flows for the operating period. This data is provided in Table 3.1-4. The post-closure

period is defined as the period during which a final cover system is in place. The landfill cells

for the covered landfills overlap the cells provided in Table 3.1-2, and the first column of each

table can be used to cross-reference information. When more comprehensive time-varying data

was reported in documents, the data are provided in Appendix B.

3.1.2.1 Analysis of Scope of Data

In order to determine whether the LDS flow data found in the literature represent the different

types of landfills found across the U.S., the data were analyzed by:

C Liner type

C Liner/LDS system combination

C Waste type and region combination

C Landfill waste placement start date
7

C Level of construction quality assurance (CQA) employed

The LDS flow data found in the literature represent 5 different liner types: 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 primarily HDPE (90 percent), with 4 percent

CSPE, 4 percent PVC, and 2 percent LMDPE. The type of GM material is potentially significant

to the infiltration rate through the liner because of different installation techniques; CSPE liners

are typically installed using solvent seaming while HDPE liners are typically installed using

thermal seaming. The distribution of the LDS flow data by GM material and liner type is shown

in Figure 3.1-1. HDPE is the only GM type well represented in all the liner types. 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 LDS drainage material is important in determining the infiltration rate through the

liner from LDS flows because cells with sand LDSs have a substantially large potential to release

construction and compression water to the LDS over time, especially during initial and early

active periods of cell operation. By contrast, geonet LDSs drain rapidly. The LDSs for the

landfill cells are primarily geonet (53 percent) and sand (29 percent). Figure 3.1-2 shows the

distribution of LDS flow data by liner type and LDS type. For GM liners, all the LDSs are

composed of sand, geonet, or a combination of the two. For the GM/CCL liners, geonets

dominate the LDS types with some sand and gravel/geonet systems.

Figure 3.1-3 presents the LDS flow data by type of waste and U.S. region. The regions are based

on the regions defined by EPA (1998), which were selected because of the climatic differences

between the regions (i.e., average annual rainfall, potential evapotranspiration, and days below

freezing). The regions are defined as follows:

C Northeast: All states north of and including Missouri, Kentucky, West Virginia, and

Maryland and east of and including Wisconsin, Illinois, and Missouri.

C Southeast: All states south of and including Arkansas, Tennessee, and Virginia, and east

of and including Arkansas and Texas.

C West: All states west of and including Minnesota, Iowa, Kansas, Oklahoma, and New

Mexico.

As demonstrated in the figure, the landfill cells are mostly MSW cells located in the Northeast.

This is not unexpected since the Northeast is rather densely populated and several states in the

Northeast require double liner systems for MSW landfills. The data collected was sparse for ISW

landfills (5) and Western landfills (13), and therefore, should not be considered representative of

these types. In general, however, the type 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 performance. 
8

The LDS flow data collected is generally representative of modern landfills (constructed within

the last 15 years). Figure 3.1-4 shows the distribution of waste placement start dates. Most of

the landfills had initial waste placement between 1987 and 1992. Modern landfills tend to be

constructed with stricter guidelines than older landfills.

The use of formal CQA procedures can 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 distribution of LDS flow data by CQA procedure and liner type. As demonstrated in

the figure, nearly all of the cells in the database have been constructed with a formal CQA

program.

3.1.2.2 Analysis of LDS Flow Data

As discussed at the beginning of this section, the significance of LDS flows varies for different

liner types. Therefore, the data in Table 3.1-2 is grouped by liner type, and the LDS flow rates

are analyzed similarly. The minimum, maximum, mean, and median values of the average

monthly LDS flows are shown for each liner type in Table 3.1-5. For those sites which only

reported weekly or daily average LDS flow (noted in Table 3.1-2), the data were excluded from

calculation of these parameters. Cumulative distribution functions of the average monthly LDS

flow rates are presented by liner type in Figure 3.1-6.

As discussed previously, the LDS flow rates for GM, GM/GCL, and GM/GCL/GM liners can

generally be considered representative of the leakage through the liner. For landfills with a sand

LDS, this is true after drainage of the sand which generally takes less than a year. For most of

the landfills with sand LDSs reported in Table 3.1-2, the average LDS flows are reported for the

period after this initial drainage period. For a few landfill cells, it is unknown whether this

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 through the

liner in addition to consolidation water. When a clay liner is compacted during construction, it

may be very nearly saturated when compaction is complete. When the clay is then subject to

compression loading, such as filling with waste, the air voids will first be lost and then water will

be expelled from the water-filled voids. The amount of and rate at which the water is expelled

due to consolidation is a function of the consolidation characteristics of the compacted clay, the

thickness, and the load placed upon it. Several papers present methods for estimating volumes of

consolidation water. Gross et al. (1990) present a method for calculating the maximum rate of

water expelled from a consolidating clay layer subject to a constant rate of load application, and

indicate that almost all the consolidation water will be expelled at the end of waste placement. 

Feeney and Maxson (1993) present a model designed to calculate the volume of fluids expelled

by the primary clay liner under simulated waste loading conditions. The model was compared to

actual flow rate data from landfill cells and generally matched the pattern and magnitude. 

Bergstrom et al. (1993) use a conventional approach to estimate volumes of consolidation water.

These estimates are compared to actual LDS flows from landfill cells, and indicate that
9

consolidation water can be expelled long after loading of a landfill cell ceases. Additionally,

Bergstrom et al. (1993), EPA (1998), and Workman (1993) use chemical characteristics of the

LDS flows to assess whether leakage is occurring through 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 information to determine actual

rates of infiltration through GM/CCL or GM/GCL/CCL liners due to leakage alone. 

One potentially important parameter in terms of the effect on the leakage rate through the liner is

the CQA procedures employed. For the LDS flow data, 95 percent of the data was reported with

an assessment of the CQA procedure. For the most part, a formal CQA program was employed. 

Table 3.1-6 compares the statistics of the average monthly LDS flow rates for all cells, cells

constructed with formal CQA procedures, and cells constructed with no formal CQA procedures. 

Table 3.1-6 is organized by liner type; only GM and GM/CCL liner types are reported, since for

all cells with other liner types, only formal CQA procedures were followed. As demonstrated in

the table, the LDS flows are higher for cells constructed with no formal CQA program for GM

liners. However, for GM/CCLs, the opposite is true, which is contrary to findings in the

literature (e.g., EPA 1998). Also, the difference between LDS flows for landfills constructed

with good CQA and all cells is negligible. The conflicting results are likely a result of the fact

that there are few cells in the database constructed without a formal CQA program.

The LDS flow measurement period is important in determining whether the data are

representative of a typical landfill’s operational life. For some landfills, the LDS flows may have

been measured for the entire operational life, while for others, LDS flows may have been

measured for only a subset of the operational life. This information was generally not available

in the literature; only the period of measurement was reported. Table 3.1-7 presents the mean,

median, minimum, and maximum of the reported LDS flow measurement periods by liner type. 

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

type in Figure 3.1-7. In general, the flow measurement periods are similar for the major liner

types, and average about 2-1/2 years.

 

Table 3.1-8 provides the statistics of the average monthly LDS flow rates by liner type for the

landfills during the post-closure period. In general, the average monthly LDS flows during the

post-closure period are significantly less than the LDS flows during the operating period. This is

expected, since the amount of water reaching the liner is limited by the cover. For the GM/GCL

liner, however, the mean, median, and maximum LDS flow rates during the post-closure period

are slightly larger than the LDS flows during the operating period. This is due to a combination

of two factors: 1) the data are limited for GM/GCL liners; and 2) the fact that for the one landfill

cell (G231) with the highest flows during the post-closure period, the LDS flows are higher

during the operating period than during the post-closure period.

3.1.3 Calculated Leakage Rates
10

Numerous studies have been performed to evaluate the frequency and size of holes and other

leaks in GM liners using electrical leak location surveys (Darilek et al. 1989; Laine 1991; Laine

and Darilek 1993; Laine and Miklas 1989; McQuade and Needham 1999; Mosley and Crozier

1995; Peggs 1993; Rollin et al. 1999). In an electrical leak location survey, an electrical power

supply is connected to electrodes above and below the liner. When no leaks are present, the

voltage impressed across the liner produces a very low current flow and relatively uniform

voltage distribution in the material above the liner. Holes in the GM are indicated by anomalies

in the potential gradient caused by the electrical current flowing through the hole. 

Table 3.1-9 presents the leak densities from the leak location surveys presented in the literature.

The leak density for 247 sites is presented along with the range of hole size, characteristics of the

leaks, and characteristics of the waste management unit, when available. Note that data from

Darilek et al. (1989) was excluded from the table because it is believed to be the same data as in

Laine and Miklas (1989). Additional information on leak densities is presented in Mosley and

Crozier (1995) which is also not included in Table 3.1-9. This data is presented for 169 sites in

the form of a graph of the number of sites surveyed versus the leak density. No site-specific

information is provided, and the data is not presented in a form that would be easily converted to

a table. The average leak density from this data is reported as 22.11 leaks/ha. 

The leak densities range from 0 to 774 leaks per 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 represent a range of site sizes (90 to 67,100 m2). Of the

124 sites where the leaks were fully broken down by leak type, 78 percent were identified as

holes, 9 percent were identified as knife cuts or tears, and 13 percent were identified as seam or

weld defects. Information that may potentially be related to the leak density (e.g., the type of

waste and WMU, CQA procedures, liner type) is limited. Table 3.1-10 presents the mean,

minimum, maximum, and median leak densities for all cells, cells with good CQA procedures

and cells with HDPE liners; analysis by other factors was not performed due to the limited data

available. The table demonstrates that the leak densities at cells constructed with a formal CQA

program and cells with HDPE liners are significantly less than the leak densities for all sites.

A small amount of data on leak densities for GMs covered with soil covers was found in the

literature. Assessment of leaks after placement of the soil cover is important since, during cover

placement, the liner can be damaged by the equipment used to place the cover, tools used to

spread the material, sharp rocks in the soil, or other mechanisms. Leak surveys of soil-covered

GMs are more difficult than uncovered liners because 1) inhomogeneities in the soil cover may

reduce the signal strength, 2) there is a decreased ability of the electrodes to detect leak signals

because of the dissimilarity of the soil and water medium, and 3) the probe cannot be used close

to the GM liner (Laine and Miklas 1989). Information was found on two specific sites where

leak location surveys were made on soil-covered GMs (Darilek et al. 1989; Laine and Darilek

1993) and on leak densities for 17 additional sites (Mosley and Crozier 1995). Table 3.1-11

presents a distribution of leak density compiled from all sources. 
11

Significantly less data was found in the literature on the sizes of the leaks (Table 3.1-12). As

demonstrated in the table, in general, only ranges of leak sizes were reported. Not enough

information was presented in the literature to develop a distribution of leak size.

A method for calculating leakage rates through defects in GM and composite liners is presented

in Bonaparte et al. (1989), Giroud and Bonaparte (1989a,b), and Giroud et al. (1992). Leakage

through GM holes is considered via the following cases:

Geomembrane Alone. If a GM with a hole is overlain and underlain by high-permeability

materials (such as a geonet or coarse gravel), flow through the hole is not significantly impeded. 

In this case, flow can be considered as free flow through an orifice, which can be evaluated by

Bernoulli’s equation (Table 3.1-13).

Geomembrane Composite Liner. If a GM with a hole is placed on a layer of low-permeability

soil to form a composite liner, the low-permeability soil significantly impedes the flow of liquid

through the hole, provided that the GM is in close contact with the low-permeability soil. It has

been shown that it is nearly impossible to achieve such close contact as to prevent lateral flow

between the GM and underlying soil, and that a key factor in influencing the rate of leakage

through a composite liner is the quality of contact between the GM and low-permeability soil

(Giroud and Bonaparte 1989a). Two empirical equations were developed based on a method of

interpolation of experimental and theoretical results on contact quality (Bonaparte et al. 1989);

these equations are shown in Table 3.1-13.

Geomembrane Overlain by Drainage Material. If a GM with a hole resting on a high

permeability material is overlain by medium-permeability drainage 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, leakage rates were calculated for the three types of liners

discussed above. Since information in the literature on hole sizes is limited, calculations are

performed for two hole sizes, 3.1 mm2 and 1 cm2. 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 performance. 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 material, the

conductivity of the drainage material was assumed to be 10-2 cm/s. Calculations were performed

for several liquid depths, using the mean and median hole frequencies, 43 leaks/ha and 8.3

leaks/ha respectively, as discussed earlier in the section. The calculated leakage rates are

presented in Tables 3.1-14 and 3.1-15 for the 3.1 mm2

 and 1 cm2

 hole sizes, respectively.

Additionally, Wilson-Fahmy and Koerner (1995) present a finite difference method for

calculating the leakage rate through a hole in a GM overlying 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 hydraulic conductivity, and the thickness of the bentonite
12

component of the GCL. The transmissivity was determined to have the most significant effect on

the leakage rates. Table 3.1-16 presents the leakage rates by transmissivity and conductivity

calculated for a 0.8 cm2 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 calculated leakage rates through GM liners as presented

in the previous two sections. The actual leakage rates are compared to the calculated leakage

rates for the GM overlain with drainage material, since nearly all of the GM liners in the database

have a LCRS composed of sand or a sand/gravel combination. Since the depth of the liquid is

not known, the range of calculated leakage rates over the range of liquid depths analyzed is used

for the comparison. For both the mean and median values, the actual leakage rates are on the

lower end of the range calculated for the smaller hole size.

For GM/GCL liners, an adequate comparison between actual and calculated leakage rates cannot

be made, because the leak density data only apply to GM liners. However, in comparing the

calculated leakage rates through a single hole (7,300 to 10-7 lphd) to the actual leakage rates

(mean of 3.9 lphd), it is clear that the calculated leakage rates are much larger that the actual

leakage rates. 

Comparisons between actual and calculated leakage rates are not made for GM/CCL liners, since

the actual leakage rate for these liners can not be determined from LDS flows. 

3.2 Geosynthetic Clay Liners

A GCL is a factory-manufactured, hydraulic barrier typically consisting of bentonite clay (or

other very low permeability materials), supported by geotextiles and/or geomembranes held

together by needling, stitching, or chemical adhesives. GCLs are typically used in areas where

clay is not readily available or where conserving air space is an important factor. GCLs do not

have the level of long-term field performance data that are available for GMs or CCLs because

GCLs were developed recently (1986) and they are typically used with a GM in a composite liner

system.

3.2.1 Review of Literature

Only one document was found during the literature survey that discusses the performance of

GCLs when installed as a single in-service liner (Lichtwardt and Comer 1997). Numerous other

documents on the GCL technology and laboratory experiments on different types of GCLs are

available in the literature; these were not acquired since they are beyond the scope of this report. 
13

3.2.2 Performance Data

In the single document on GCL performance (Lichtwardt and Comer 1997), a GCL was installed

on the bottom of a salinity-gradient solar pond in Texas in 1994. The pond has a surface area of

approximately 1 acre and a water depth averaging 3.2 meters. The GCL is a modified Gundseal,

with a 30-mil flexible polypropylene geomembrane backing with 0.5 cm of bentonite clay

bonded to one side. The performance of the GCL is presented as the variation in hydraulic

conductivity of the GCL over time for a 9-week period. The hydraulic conductivity remains

fairly constant at 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 represents the unique

environment of a salinity-gradient 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 natural mineral materials (natural soils), bentonite-soil blends, and other

materials placed and compacted in layers called lifts. CCLs can be designed to work effectively

as hydraulic barriers, assuming that selected liner materials are suitable, liner materials are

properly placed and compacted, and the completed liner is properly protected before, during, and

after construction.

For CCLs, performance evaluation usually consists of measuring the field hydraulic conductivity

of the liner. The two most common methods used to estimate the hydraulic conductivity are

collection lysimeters and infiltrometers. Both of these methods measure the infiltration rate

through the CCL and use it to calculate the conductivity. Lysimeters are collection basins

installed beneath a portion of the liner. Water that infiltrates through the liner above the basin is

collected and routed via pipes for discharge measurement and chemical analysis. The infiltration

rate through the CCL can be determined by dividing the discharge by the area of the lysimeter. 

A long period of monitoring (several weeks to several months) is required in order for the

collection lysimeter to give steady-state infiltration rates. At least one state, Wisconsin, requires

lysimeters for monitoring of landfill performance. Infiltrometers directly 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 sealed ring or box that

measures infiltration into a relatively large area, is the most appropriate 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 weeks to several months) to ensure that the

infiltration rate has reached steady-state. More 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, evaporation, and pond filling rate to determine

leakage through the liner. Drawbacks to this method include potential problems with accurately

measuring the amount of rainfall and evaporation that occurs.
14

3.3.1 Review of Literature

In the literature review, documents were collected that contained information on infiltration rates

and hydraulic conductivities of CCLs. There was often overlap of infiltration and conductivity

data in these sources, as field infiltration rates are used to calculate the field hydraulic

conductivities. The comparison of field to lab hydraulic conductivity is a topic that is heavily

discussed in the literature, so the documents collected often contained both field and lab values

of hydraulic conductivity. Documents that contained only laboratory values of hydraulic

conductivity were not collected and reviewed. 

A limited amount of data was found on infiltration rates through CCLs. Even though infiltration

data is often collected during testing for hydraulic conductivity, the infiltration data is often not

reported in the literature. Most of the sources with infiltration data also report hydraulic

conductivity: Albrecht and Cartwright (1989), Daniel (1984), Gordon et al. (1989), King et al.

(1993), Rogowski (1985), O'Sadnick et al. (1995), and Trautwein and Williams (1990). Two

additional sources were collected that contained infiltration data only: Cartwright and Krapac

(1990) and Huebner and Gordon (1995). The data on infiltration rates from these documents is

presented in Section 3.3.2.

Data on field hydraulic conductivities of CCLs are much more prevalent in the literature. This is

because conductivity is the key performance parameter found in regulatory documents. The

primary source of CCL hydraulic conductivity data is EPA (1998). This report contains a

database of 89 CCLs (8 in-service and 81 test pads) with hydraulic conductivity and other

properties of landfill liners. This report also contains a smaller database of field hydraulic

conductivities for 11 test pads that had bentonite added to the natural clay soil. Six separate

documents were found that use or contain the same data in these databases: Benson et al. (1999),

Bergstrom et al. (1995), Gordon et al. (1989), Johnson et al. (1990), O'Sadnick et al. (1995), and

Reades et al. (1990) . Benson and Daniel (1994) contains data on field hydraulic conductivity for

CCLs, some of which overlap with liners from EPA (1998) and other sources collected. In

addition to the EPA (1998) report and the other references listed above, 9 other sources were

collected containing hydraulic conductivity data: Albrecht and Cartwright (1989), Day and

Daniel (1985), Daniel (1984), Elsbury et al. (1990), Gordon et al. (1984), Luettich et al. (1995),

Rogowski (1985), Trast and Benson (1995), and Trautwein and Williams (1990). The data from

these documents is presented in Section 3.3.3.

3.3.2 Infiltration Data

Infiltration data for CCLs 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 days to 13 years. In general, the measurement period is shorter for test pads (40

days to 2 years) than for the actual sites (90 days to 13 years). The measurement methods used

are infiltrometers, lysimeters, and water balance; each was used at three of the sites reported. For
15

the water balance and infiltrometer methods, a direct infiltration rate is typically reported. For

the lysimeters, a volume collected per time period and the lysimeter area are reported; the

infiltration rate is calculated from this data. O'Sadnick et al. (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 average 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 limited amount of data

available on infiltration rates, these data are not necessarily representative of infiltration rates

through CCLs across the U.S. 

3.3.3 Hydraulic Conductivity Data

Hydraulic conductivity values from all collected sources are presented in Table 3.3-2. Field

hydraulic conductivity values, along with site characteristics, liner characteristics, and lab

hydraulic conductivity values, where available, 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 are not reported as one or the other. Of the 11 in-service units, 8 are landfills

and 3 are ponds. 

The parameters appearing in Table 3.3-2 were selected because they potentially have a significant

relationship to the hydraulic conductivity values. Table 3.3-3 lists the percentage of sites

reporting each of the parameters. Less than 10 percent of the sites report construction date or

monitoring period. All of the liner characteristic parameters except for the clay fraction are

reported for at least 60 percent of the sites. All of the construction parameters are reported for 50

to 75 percent of the sites. Among the quality assurance parameters, all are reported for at least

half of the sites with the exception of frequency of moisture density tests, which is rarely

reported. The laboratory hydraulic conductivity is reported for 72 percent of liner sites. 

3.3.3.1 Analysis of Scope of Data

In order to determine whether the data found in the literature represent the different types of

CCLs found across the U.S., the data were analyzed by:

C Liner type

C Region 

C Level of CQA employed

The largest amount of data was found for test pads, which comprise 120 out of 149 liner sites in

the database. Data on in-service CCLs is limited likely due to the fact that CCLs are often used

in conjunction with GM liners and few in-service CCLs are usually constructed with instruments

allowing documentation of their performance. There are 137 natural clay liners in the database

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

necessarily representative of this liner type. 
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 database contains the most data for liner

sites in the Southeast. The least number of sites occur in the West (15), despite the fact that this

is the largest geographic region. Note that only 56 percent of sites report location data. 

The use of formal CQA procedures can have a significant influence on the liner’s field hydraulic

conductivity. Of the 149 liner sites, 69 percent were constructed with a formal CQA procedure,

5 percent were not, and this information was not reported for 26 percent of the sites. Note,

however, that the database in EPA (1998) only included liners that were constructed with CQA

in general accord with industry practices; liners constructed with poor CQA were specifically

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 leakage than expected, in part

because of insufficient CQA. 

3.3.3.2 Analysis of Hydraulic Conductivity Data

The mean, median, minimum, and maximum values of field hydraulic conductivity are shown for

natural clay, soil/bentonite, and all liners in Table 3.3-4. These statistics are shown for landfill

sites, pond sites, test pads, and all liner sites in Table 3.3-5. Though there are limited data for

landfills, the average hydraulic conductivity for these in-service units is an order of magnitude

lower than the average hydraulic conductivity for the test pads. The lower conductivity may be a

result of several factors, including 1) the compressive 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 generally thicker than the test pad liners. As discussed previously, there is not

enough data to characterize soil/bentonite liners, landfill liners, or pond liners separately. For the

purpose of developing a distribution of field hydraulic conductivity, it may be appropriate to use

all of the data as characteristic of CCLs as a general class. 

A cumulative distribution function of all field hydraulic conductivity values collected for this

study is presented in Figure 3.3-2 . The common regulatory criterion of 10-7 cm/s is also shown

on this figure. The figure illustrates that 70 percent of liner sites reviewed for this study have a

field hydraulic conductivity value of less than or equal to 10-7 cm/s. 

Figure 3.3-3 presents a scatter plot of field versus laboratory hydraulic conductivity values. This

plot also shows lines representing several ratios of lab to field values. The figure shows that

most of the data lies below the 1:1 line, which means that laboratory tests usually under-predict

field values of hydraulic 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 as 4 orders of magnitude greater than the corresponding lab value. 

The reliability of laboratory hydraulic 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. It is generally believed that laboratory

measurements, which occur on a small-scale, will yield the same conductivity as field
17

measurements, which occur on a large-scale, if the clay liner is well-constructed and reasonably

homogeneous; the reverse is also believed to be true.

4.0 Summary and Recommendations

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 infiltration rates for surface impoundments or waste piles. A database of average

monthly LDS flow data was compiled which contains 259 landfill cells. The database can be

summarized as follows:

C Generally, the GM, GM/CCL, and GM/GCL liners are well represented, with over 30

cells each. HDPE is the only type of GM material well represented in all the liner types.

C Both sand and geonet LDSs are well represented for GM and GM/CCL liners.

C The LDS data primarily represent MSW cells located in the Northeast. The data collected

was sparse for ISW landfills and Western landfills and therefore, should not be

considered representative of these types. 

C The LDS flow data collected 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 been constructed with a formal CQA program.

The information on average monthly LDS flows from the landfill database is summarized as

follows:

C The LDS flow rates for GM liners range from 1 to 4,282 lphd, with an average of 258

lphd. These flow rates can generally be considered representative of the leakage through

the liner. 

C The LDS flow rates for GM/GCL liners range from 0 to 32 lphd, with an average of 4

lphd. These flow rates can generally be considered representative of the leakage through

the liner.

C The LDS flow rates for GM/CCL liners range from 0 to 1410 lphd, with an average of

130 lphd. LDS flows for these liners typically represent leakage through the liner plus

consolidation water. Actual rates of infiltration through GM/CCL liners due to leakage

alone cannot be determined. 

C An analysis of the data by CQA level showed conflicting results, likely due to the fact

that few cells in the database were constructed without a formal CQA program.

C A limited amount of data on LDS flow rates for landfills during the post-closure period

was also compiled. In general, for GM and GM/CCL liners, the average monthly LDS

flows during the post-closure period are significantly less than the LDS flows during the

operating period.
18

For GM and composite liners, infiltration rates through liners were also calculated based on the

frequency and size of defects in the GM liner. The following observations resulted from this

analysis: 

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

hectare. 

C A limited amount of data was collected on the sizes of leaks. Leak sizes range from

pinholes to a 30-cm seam defect.

C A method for calculating leakage rates through defects in GM and composite liners is

presented for a GM alone, a GM composite liner, and a GM overlain by drainage

material. Leakage rates were calculated for these three liners for two hole sizes. The

actual leakage rates are compared to the calculated leakage rates for the GM overlain with

drainage material, since nearly all of the GM liners in the database have a LCRS

composed of sand or a sand/gravel combination. The actual leakage rates are on the lower

end of the range calculated for the smaller hole size.

4.2 Geosynthetic Clay Liners

For GCL liners, only a single document on infiltration through a GCL was found. The hydraulic

conductivity of the GCL over a 9-week period was 2 x 10-6 cm/s. The data presented in this

paper represents the unique environment of a salinity-gradient solar pond (which includes high

temperature, high salinity and low pH), which may not be representative of GCL use in other

situations.

4.3 Compacted Clay Liners

For CCLs, infiltration rates estimated using three methods, lysimeters, infiltrometers, and water

balance, were found in the literature. However, infiltration rates were only found for 9 sites. 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. Due to the limited amount of data available, these data are not necessarily

representative of infiltration rates through CCLs across the U.S. 

Hydraulic conductivity data was also collected for CCLs. A database of field hydraulic

conductivity values was compiled which contains 149 liners. The database can be summarized

as follows: 

C The data mostly represent test pads (80 percent), with 7 percent in-service WMUs and for

the remainder, this information was not reported. 

C There are 137 natural clay liners in the database and 12 soil/bentonite liners.

C Most of the liner sites are located in the Southeast and only a few sites are in the West.

Only 56 percent of sites report location data. 

C Most of the liners were constructed with a formal CQA procedure (69 percent); 5 percent

were not and for the remainder, this information was not reported.
19

The information on field hydraulic conductivities from the database is summarized as follows:

C The field hydraulic 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 hydraulic 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 represent 12 liners, and

cannot be considered representative of soil/bentonite liners in general.

C Not enough data was available to characterize WMUs (e.g., landfills, ponds) separately.

C Seventy percent of liner sites in the database have a field hydraulic conductivity value of

less than or equal to 10-7 cm/s, the common regulatory criterion. 

C A comparison of field hydraulic conductivities to laboratory hydraulic conductivities

demonstrates that laboratory tests typically under-predict field values of hydraulic

conductivity. This concurs with observations reported in the literature.

4.4 Recommendations

Based on the findings in this report, the following are recommended:

C For GM and composite liners, the type of LDS drainage material, the level of CQA

performed, and the type of GM material have a potentially significant influence on LDS

flow rates. Further investigation of the relationship between these parameters and the

LDS flow rates should be performed. If a significant relationship is determined, and

sufficient data are available, different distributions could be created for different

categories based on these parameters. For example, a distribution could be created for

HDPE liners with good CQA and a geonet drainage system. 

C For GM/CCL liners, leakage rates are difficult to determine because of the presence of

consolidation water in the LDS system. Several studies present methods for addressing

this issue, though not for isolating LDS flows due to leakage alone. These methods could

be investigated further to determine if a distribution of leakage rates could be developed

for GM/CCL liners.

C For CCLs, not enough information was available on infiltration rates to adequately

develop a distribution. However, information on field hydraulic conductivities was

plentiful. The relationship between the liner characteristics and construction information

is potentially related to the field hydraulic conductivity values. If a distribution of field

hydraulic conductivities is desired, the relationship between the conductivity and these

parameters should be investigated. This could be done by creating scatter plots relating

the conductivity to each parameter individually, and using regression techniques,

including multiple regression, to determine the significance of the relationship. Once the

relationships have been determined, the conductivities can be categorized by the most

significant parameters, and distributions of conductivities can be generated for those

categories. Some investigation into the relationship between hydraulic conductivity and

the liner characteristics and construction data has been performed in EPA (1998).
20

C The time-variability of leakage rates should be investigated further. In this report,

average leakage rates are provided for GM and composite liners for two time periods,

during operation and post-closure; significantly less leakage is observed during the postclosure period. Several literature sources present time-variable infiltration rates

(contained in Appendix B), which could be analyzed for a potential relationship. The

current LDS flow database can also potentially provide useful information related to a

time-series analysis, such as a distribution of landfill operating life. No information was

found in the literature on the time-variability of infiltration rates or hydraulic

conductivities of CCLs. This is potentially important, as the long-term performance of a

CCL cannot be addressed without this information.

5.0 References

Albrecht, K.A. and K. Cartwright. 1989. Infiltration and hydraulic conductivity of a compacted

earthen liner. Ground Water, vol. 27, no. 1, pp. 14-19.

Benson, C.H. and D.E. Daniel. 1994. Minimum thickness of compacted soil liners: II. Analysis

and case histories. Journal of Geotechnical Engineering, vol. 120, no. 1, January, pp. 153-172.

Benson, C.H., D.E. Daniel, and G.P. Boutwell. 1999. Field performance 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. Benson. 1995. Field performance of a

double liner test pad. Geoenvironment 2000: Characterization, Containment, Remediation, and

Performance in Environmental Geotechnics. Geotechnical Special Publication No. 46, ASCE,

New York.

Bergstrom, W.R., M.J. Takacs, and M.A. Olson. 1993. Behavior of five operating landfill leak

detection systems. Proceedings, Waste Tech '93, Marina Del Rey, California.

Bonaparte, R. 1995. Long-term performance of landfills. Geoenvironment 2000:

Characterization, Containment, Remediation, and Performance in Environmental Geotechnics. 

Geotechnical Special Publication No. 46, ASCE, New York.

Bonaparte, R. and B.A. Gross. 1990. Field behavior of double-liner systems. Waste Containment

Systems: Construction, Regulation, and Performance, Geotechnical Special Publication No. 26,

ASCE, New York.

Bonaparte, R. and B.A. Gross. 1993. LDCRS Flow from Double Lined Landfills and Surface

Impoundments. EPA/600/R-93/070. NTIS Publication PB93-179885. Risk Reduction

Engineering Laboratory, Office of Research and Development, U.S. EPA, Cincinnati, OH.

Bonaparte, R., J.P. Giroud, and B.A. Gross. 1989. Rates of leakage through landfill liners. 
21

Geosynthetics 1989 Conference, 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 Performance,

Geotechnical Special Publication No. 26, ASCE, New York.

Daniel, D.E. 1984. Predicting hydraulic conductivity of clay liners. Journal of Geotechnical

Engineering, vol. 110, no. 2, pp. 285-300.

Daniel, D.E. 1989. In-situ hydraulic conductivity tests for compacted clays. 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 location method for

geomembrane liners: development and applications. Proceedings of the Geosynthetics '89

Conference, San Diego, pp. 456-466.

Day, S.R. and D.E. Daniel. 1985. Hydraulic conductivity of two prototype 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 after eight years of service. Geotextiles and

Geomembranes, vol. 15, pp. 277-287.

Elsbury, B.R., D.E. Daniel, G.A. Sraders, and D.C. Anderson. 1990. Lessons 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 systems in landfills. 

Geosynthetics ‘93 Conference Proceedings. Industrial Fabrics Association International, St.

Paul, MN.

Giardino, V.G. and J.L. Guglielmetti. 1997. Long-term performance of a hazardous waste

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 defects". Geotextiles and Geomembranes, vol. 11, pp.

1-28.

Giroud, J.P. and R. Bonaparte. 1989a. Leakage through liners constructed with

geomembranes-Part I. Geomembrane liners. Geotextiles and Geomembranes, vol. 8, pp. 27-67.

Giroud, J.P. and R. Bonaparte. 1989b. Leakage through liners constructed with

geomembranes-Part II. 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 performance of four

clay-lined landfills 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. Huebner, and T.J. Miazga. 1989. Hydraulic conductivity of three landfill

clay liners. Journal of Geotechnical Engineering, vol. 115, no. 8, pp. 1148-1160.

Gross, B.A., R. Bonaparte, and J.P. Giroud. 1990. Evaluation of flow from landfill leakage

detection layers. International Conference on Geotextiles, Geomembranes, and Related Products,

The Hague, Netherlands.

Hartley, Robert P. 1992. Surface Impoundments, Design, Construction, and Operation. Noyes

Data Corporation, Park Ridge, New Jersey.

Huebner, P.M., and M.E. Gordon. 1995. Estimating contaminant breakthrough for a clay-lined

municipal solid waste landfill. Geoenvironment 2000: Characterization, Containment,

Remediation, and Performance in Environmental Geotechnics. Geotechnical Special Publication

No. 46, ASCE, New York.

Johnson, G.W., W.S. Crumley, and G.P. Boutwell. 1990. Field verification of clay liner

hydraulic conductivity. Waste Containment Systems: Construction, Regulation, and

Performance, Geotechnical Special Publication No. 26, ASCE, New York.

King, K.S., R.M. Quigley, F. Fernandez, D.W. Reades, and A. Bacopoulos. 1993. Hydraulic

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 leaks located in geomembrane liners using the

electrical leak location method: Case histories. Proceedings, 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. Locating leaks in geomembrane liners of landfills covered

with a protective soil. Geosynthetics 93 Conference Proceedings. Industrial Fabrics Association

International, St. Paul, MN.

Lichtwardt, M.A. and A.I. Comer. 1997. Geosynthetics in a salinity-gradient solar pond

environment. Geosynthetics ‘97 Conference Proceedings. Industrial 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 materials. Geoenvironment 2000: Characterization, Containment,

Remediation, and Performance in Environmental Geotechnics. Geotechnical Special Publication

No. 46, ASCE, New York.

Maule, J., R.K. Lowe, and J.L. McCulloch. 1993. Performance evaluation of synthetically lined

landfills. Tappi Journal, vol. 76, no. 12, pp.172-176.

McQuade, S.J. and A.D. Needham. 1999. Geomembrane liner defects-causes, frequency, and

avoidance. Proceedings of the Institution of Civil Engineers, Geotechnical Engineering, vol.

137, no. 4, pp. 203-213.

Mosley, N.G. and F. Crozier. 1995. Application of a geomembrane leak location survey at a UK

waste disposal facility. Engineering 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. Geotechnical Special Publication No. 46, ASCE,

New York.

Othman, M.A., R. Bonaparte, and B.A. Gross. 1997. Preliminary results of composite liner field

performance study. Geotextiles and Geomembranes, vol. 15, nos. 4-6, pp. 289-312.

Peggs, I.D. 1993. Practical geoelectric leak surveys with hand-held, remote, and water lance

probes. Proceedings of Geosynthetics '93, vol. 3, IFAI, Vancouver, pp. 1523-1532.

Phaneuf, R.J. No Date. A state's perspective on CQA/CQC in environmental containment

system design & construction. New York State Department of Environmental Conservation's

Division of Solid Waste, Albany, NY.

Reades, D.W., L.R. Lahti, R.M. Quigley, and 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 leakage from landfills with modern liner

systems. Water Resources Bulletin, vol. 32, no. 4, pp. 697-709.

Rogowski, A.S. 1985. Effectiveness of a compacted clay liner in preventing ground water

contamination. Proceedings of the Fifth National Symposium 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 exposed
24

geomembrane liners using an electrical leak detection technique. Geosynthetics ‘99 Specifying

Geosynthetics and Developing Design Details, vol. 2, pp. 615-626.

Sai, J.O. and D.C. Anderson. 1990. Field hydraulic conductivity tests for compacted soil liners. 

Geotechnical Testing Journal, GTJODJ, vol. 13, no. 3, September, pp. 215-225.

Tedder, R.B. 1997. Evaluating the performance of florida double-lined landfills. Geosynthetics

‘97 Conference Proceedings, IFAI, St. Paul, Minnesota, pp. 425-438.

Trast, J.M. and C.H. Benson. 1995. Estimating field hydraulic conductivity of compacted clay. 

Journal of Geotechnical Engineering, vol. 121, no. 10, pp. 736-739.

Trautwein, S.J. and C.E. Williams. 1990. Performance evaluation of earthen liners. Waste

Containment Systems: Construction, Regulation, and Performance, Geotechnical Special

Publication No. 26, ASCE, New York.

U.S. EPA. 1992. Action Leakage Rates for Leak Detection Systems. Supplemental Background

Document for the Final Double Liners and Leak Detection Systems Rule for Hazardous Waste

Landfills, Waste Piles, and Surface Impoundments. EPA/530-R-92-004. NTIS Publication

PB92-128214. Office of Solid Waste, Washington, D.C. January.

U.S. EPA. 1996. Report of 1995 Workshop on Geosynthetic Clay Liners. EPA/600/R-96/149. 

Office of Research and Development, Washington, D.C.

U.S. EPA. 1998. Assessment and Recommendations for Optimal Performance of Waste

Containment Systems. Office of Research and Development, National Risk Management

Research Laboratory, Cincinatti, Ohio. Draft Final.

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

Solid Waste and Emergency Response, Washington, D.C.

U.S. EPA. 1999b. Technical Background Document: Industrial Waste Management Evaluation

Model (IWEM), Ground Water Model to Support the Guide for Industrial Waste Management. 

EPA530-R-99-002.

U.S. EPA. 1999c. User’s Guide for the Industrial Waste Management Evaluation Model

(IWEM): Tier 1 Look-Up Tables and Tier 2 Neural Networks. EPA530-R-99-003.

Wilson-Fahmy, R.F. and R.M. Koerner. 1995. Leakage rates through holes in geomembranes

overlying geosynthetic clay liners. Geosynthetics 95 Conference Proceedings, IFAI, St. Paul,

Minnesota, pp. 655-668.

Workman, J.P. 1993. Interpretation of leakage rates in double-liner systems. Proceedings, 7th
25

Geosynthetic Research Institute Seminar, Drexel University, Philadelphia, Pennsylvania, pp.

95-112.
26

Figure 3.1-1. Distribution of LDS Flow Data by Geomembrane Material and Liner Type

for Geomembrane and Composite Liners. 

Figure 3.1-2. Distribution of LDS Flow Data by Liner Type and LDS Type for

Geomembrane and Composite Liners.
27

Figure 3.1-3. Distribution of LDS Flow Data by Type of Waste and Region for

Geomembrane and Composite Liners.

Figure 3.1-4. Distribution of Waste Placement Start Dates for Geomembrane and

Composite Liners.
28

Figure 3.1-5. Distribution of LDS Flow Data by CQA Procedure and Liner Type for

Geomembrane and Composite Liners.

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

Type for Geomembrane and Composite Liners.
29

Figure 3.1-7. Cumulative Distribution Functions of LDS Flow Measurement Period by

Liner Type for Geomembrane and Composite Liners.

Figure 3.1-8. Cumulative Distribution Function of Leak Densities for Geomembrane

Liners.
30

Figure 3.3-1. Number of Compacted Clay Liner Sites by U.S. Region.

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

for All Compacted Clay 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 Address Years

Covered

Summary

EI Compendex Engineering

Information, Inc.

http://www.ei.org 1970-present A bibliographic database containing over 5 million records

and references to more than 5,000 engineering journals and

conferences.

National Technical

Information Service

(NTIS)

U.S. Department

of Commerce

http://www.ntis.gov 1990-present

(searchable);

older

documents

available

Largest, central resource for government-funded scientific,

technical, engineering, and business related information with

over 2 million publications covering over 350 subject areas.

DIALOG A Thomson

Company

http://www.dialog.com 1964-present Database of abstracts from Pollution Abstracts,

Environmental Bibliography, JICST-EPlus - Japanese Science

& Technology, PASCAL

sciBASE The Scientific

World

http://thescientificworld.com 1993-present Database of scientific, technical and medical research

literature, including approximately 12 million articles

published since 1993 in more than 20,000 journals. 

California Digital

Library (Melvyl and

Periodicals database)

University of

California

http://www.cdlib.org Variable Melvyl contains records for materials (books, archives,

audio-visuals, computer files, videorecordings, dissertations,

government documents, maps, music scores, and recordings)

in the libraries of the nine UC campuses, California State

Library, California Academy of Sciences, California Historical

Society, Center for Research Libraries, and the Graduate

Theological Union. The Periodicals Database allows users to

search the titles of serials (periodicals, newspapers, annuals,

some monographic series, and other ongoing publications)

owned by more than 550 California libraries. 

National Service

Center for

Environmental

Publications (NSCEP)

U.S.

Environmental

Protection

Agency

http://www.epa.gov/ncepihom Unknown The NSCEP maintains and distributes EPA publications in

hardcopy, CD ROM and other multi-media formats. The

current publication inventory includes over 7,000 titles.

Table 2.1-1 continued.
33

Name Hosted By Web Address Years

Covered

Summary

National

Environmental

Publications

International Site

(NEPIS)

U.S.

Environmental

Protection

Agency

http://www.epa.gov/ncepihom

/nepishom/

Unknown The NEPIS contains over 6,000 full text, on line EPA

documents.

EPA Office of Research

and Development

(ORD)

U.S.

Environmental

Protection

Agency

http://www.epa.gov/ORD/

publications

Variable Collection of publications by the ORD

Web of Science Institute for

Scientific

Information (ISI)

http://www.webofscience.com 1945-present Web of Science consists of three databases: Arts &

Humanities Citation Index, Social Sciences Citation Index,

and Science Citation Index Expanded. Web of Science covers

thousands of research journals across hundreds of

disciplines. Access restricted to subscribers only.

Science Direct N/A http://www.sciencedirect.com Unknown ScienceDirect is an electronic information service offering

comprehensive coverage of literature across all fields of

science, including over 1.2 million full-text articles 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 Possible Cause/Comment

Manufacture Pinholes, excessive thickness

changes, poor stress crack

resistance

Unusual now for procedures with good quality

control. Poor resin.

Delivery Scuffing, cuts, brittle cracks,

tears, punctures

Unloading with unsuitable plant or lifting

equipment. Impact. Poorly prepared storage

areas.

Placement Scratches, cuts, holes, tears,

crimps

Dragging sheet along ground, trimming of

panels, rough subgrade, use of equipment on

top of sheet without protection layer, wind

damage, large wrinkles, folds, damage by lifting

bars.

Welding Cuts, overheating, scoring,

poor adhesion, crimping

Careless edge trimming, welding speed or

temperature incorrect, excessive grinding, dirt,

or damp in weld area, excessive roller pressure.

Cover Placement Tears, cuts and scratches,

holes, stress in membrane

Action of earthmoving plant, insufficient cover

during placement, careless probing of cover

depth. Contraction of sheet due to ambient

temperature reduction.

Post-Installation Holes, tearing, slits, cracks Puncture from drainage materials, puncture by

items of deposited waste, opening of partial

depth cuts, pulling apart of poor quality welds,

downdrag stresses caused by settling waste,

differential settlement in the base.

Source: McQuade and Needham (1999).

Table 3.1-2. LDS Flow Database for Landfill Cells with Geomembrane or Composite

Liners.

(Table provided in MS Excel)
35

Table 3.1-3. Percent of Sites Reporting Parameters by Liner Type for Geomembrane and 

Composite Liners.

Parameter

Percent of Sites Reporting Parameter by Liner Type

GM GM/CCL GM/GCL GM/GCL

/CCL

GM/GCL

/GM

All

Total Number 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 Annual Rainfall 69 61 89 100 100 68

Depth to Groundwater 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 Material 98 100 100 100 100 99

GM Liner Thickness 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 Material 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 Procedures 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 Layer 100 100 100 100 100 100

Thickness of Drainage Layer 79 63 93 100 100 72

Note: - = not applicable.
36

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

During the Post-Closure Period.

(Table provided in MS Excel)

Table 3.1-5. Statistics of Average Monthly LDS Flow Rates by Liner Type for

Geomembrane and Composite Liners.

Liner Type

Number of Sites

Reporting Data

Average Monthly LDS Flow (lphd)

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

Geomembrane and Composite Liners.

Liner Type Parameter

Average Monthly LDS Flow (lphd)

All Cells Cells Constructed

with Good CQA

Cells Constructed

with No Formal

CQA

GM Number 84 71 9

Mean 258 246 423

Median 65 53 108

Minimum 1 1 20

Maximum 4282 4282 1603

GM/CCL Number 131 117 11

Mean 130 133 64

Median 84 90 53

Minimum 0 0 9

Maximum 1410 1410 148
37

Table 3.1-7. Statistics of LDS Flow Measurement Period by Liner Type for Geomembrane

and Composite Liners.

Liner Type

Number of Sites

Reporting Data

Flow Measurement 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

Period for Landfills with Geomembrane or Composite Liners.

Liner Type

Number of Sites

Reporting Data

Average Monthly LDS Flow (lphd)

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 Density Data for Geomembrane Liners.

(Table provided in MS Excel)

Table 3.1-10. Leak Density Statistics by Potentially Significant Parameter for

Geomembrane Liners.

Parameter Number of

Sites With

Data

Leak Density (leaks/ha)

Mean Median Minimum Maximum

Formal CQA

Program Followed

26 2.03 0.92 0 12.5

HDPE Liner Type 120 6.5 1.0 0 120

All Cells 247 43 8.2 0 774
38

Table 3.1-11. Leak Density Data for Soil-Covered Geomembrane Liners.

Leak Density

(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. Ranges of Leak Sizes found in Literature for Geomembrane Liners.

Reference Holes Knife Cuts/Tears Seams/Welds Notes

Rollin et al. 1995 < 2 mm2: 25%

2-10 mm2: 50%

> 10 mm2: 25%

2-10 mm2: 40%

> 10 mm2: 60%

< 2 mm2: 66%

2-10 mm2: 26%

> 10 mm2: 8%

McQuade and

Needham 1999

range pinhole to

5000 mm

range 20 mm x 50

mm to 30 mm x 50

mm 

NA See Table 3.1-9

for site-specific

ranges

Laine and Miklas

1989

range <0.025 in to

1 in

range 0.25 in to 12

in

NA Only ranges

reported

Laine 1991 0.04 in diameter 0.04 in cut;

0.02 in x 0.006 in

flaw

0.04 in diameter Sizes not

reported for all

defects

Mosley and

Crozier 1995

NA 2 cm cut; 15 cm

cut

NA Sizes not

reported for all

defects

Peggs 1993 None None 30 cm Only one waste

cell reported
39

Table 3.1-13. Equations Representing Leakage Rates Through Holes for Geomembrane

and Composite Liners.

Geomembrane

Alone

Composite Liner Geomembrane

Overlain by

Drainage

Material Good contact Poor contact

Equation

Definitions Q = steady-state rate of leakage through one hole (m3/s)

a = area of hole in the geomembrane (m2

)

CB

 = dimensionless coefficient, for sharp edges = 0.6

g = acceleration of gravity (9.81 m/s2)

h = head of liquid on top of geomembrane (m)

ks = hydraulic conductivity of the low-permeability soil underlying the geomembrane (m/s)

kd = hydraulic conductivity of drainage material overlying the geomembrane (m/s)

Limitations Equation can be used

if soil underlying

geomembrane has

conductivity greater

than 10-3 m/s when

geomembrane hole

area is 0.1 cm2, and a

conductivity greater

than 10-2 m/s when

geomembrane hole

area is 1 cm2

.

Equation for situations

where conductivity of

low-permeability soil is

less than 10-6 m/s and

the head of liquid on

top of the

geomembrane is less

than the thickness of

the low-permeability

soil layer. Good

contact corresponds to

geomembrane

installed with as few

wrinkles as possible on

top of low-permeability

soil layer that has

been adequately

compacted and has a

smooth surface.

Equation for situations

where conductivity of

low-permeability soil is

less than 10-6 m/s and

the head of liquid on

top of the

geomembrane is less

than the thickness of

the low-permeability

soil layer. Poor contact

corresponds to a

geomembrane that has

been installed with a

certain number of

wrinkles, and/or placed

on a low-permeability

soil that has not been

well compacted and

does not appear

smooth.

Hydraulic

conductivity of

drainage material

greater than 10-6

m/s. Head of liquid

on top of

geomembrane less

than thickness of

drainage layer.

Source: Bonaparte et al. (1989).
40

Table 3.1-14. Calculated Leakage Rates (lphd) for Geomembrane and Composite Liners

Assuming Hole Size of 3.1 mm2

.

Depth of Liquid (m)

0.001 0.01 0.1 0.3

Geomembrane

alone

970 (Mean)

190 (Median)

3060 (Mean)

590 (Median)

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 (Median)

Geomembrane

Overlain with

Drainage

Material

46 (Mean)

9 (Median)

260 (Mean)

50 (Median)

1500 (Mean)

280 (Median)

3300 (Mean)

640 (Median)

Table 3.1-15. Calculated Leakage Rates (lphd) for Geomembrane and Composite Liners

Assuming Hole Size of 1 cm2.

Depth of Liquid (m)

0.001 0.01 0.1 0.3

Geomembrane

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)

Geomembrane

Overlain with

Drainage

Material

630 (Mean)

120 (Median)

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.

Transmissivity

of GM-GCL

Interface

(m2

/s)

Hydraulic conductivity 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 74,000 103,000 122,000

10-10 487,000 615,000 770,000 860,000

10-9 4 x 1064.3 x 1065.1 x 1065.6 x 106

10-8 3.1 x 1073.5 x 1073.8 x 1074 x 107

Note: Numbers are approximate since they were estimated from graphs.

Source: Wilson-Fahmy and Koerner (1995).

Table 3.1-17. Comparison of Actual Versus Calculated Leakage Rates for Geomembrane

Liners.

Actual Leakage Rate

(lphd)

Calculated Leakage Rate (lphd)

3.1 mm2 hole 1 cm2 hole

Mean 258 46-3300 630-45200

Median 65 9-640 120-8700

Table 3.3-1. Infiltration Data for Compacted Clay Liners.

(Table provided in MS Excel)

Table 3.3-2. Hydraulic Conductivity Data for Compacted Clay Liners.

(Table provided in MS Excel)
42

Table 3.3-3. Percent of Sites Reporting Parameters for Compacted Clay Liner Hydraulic

Conductivities.

Parameter Percent of Sites

Reporting Parameter

Waste Management Unit Type 38

In-Service or Test Pad 88

Measurement Method 100

Size of Test Apparatus 69

Location 56

Construction Date 7

Monitoring Period 5

Liner Characteristics

Liner Material 100

Area of Cell 64

Liner Thickness 89

Liquid Limit 77

Plasticity Index 92

Percent Fines 67

Clay Fraction 44

Percent Bentonite 75

Optimum Water Content 70

Maximum Dry Unit Weight 67

Compactive Effort 68

Construction Information

Compactor Mass 57

Passes per Lift 50

Lift Thickness 72

Number of Lifts 72

Formal CQA Program? 74

Qua lity Assu rance / Qua lity Contro l Data

Water content 70

Dry Density 69

Po 61

Frequency of Moisture Density Tests 2

Time Lapse Between Completion of Liner

and Filling With Water/Waste

1

Laboratory Hydraulic Conductivity 72
43

Table 3.3-4. Statistics of Field Hydraulic Conductivity by Liner Material for Compacted

Clay Liners.

Liner Type Number of

Sites

Reporting

Data

Field Hydraulic Conductivity (cm/s)

Mean Median Minimum Maximum

Natural Clay 137 6.5 x 10-8 5.0 x 10-8 1.0 x 10-9 1.0 x 10-4

Soil/Bentonite 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. Statistics of Field Hydraulic Conductivity by Waste Management Unit Type

for Compacted Clay Liners.

Liner Type Number of

Sites

Reporting

Data

Field Hydraulic Conductivity (cm/s)

Mean Median Minimum Maximum

Landfill 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

Test Pad 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