### 1 

# Fact Sheet on Evapotranspiration Cover Systems for Waste Containment

INTRODUCTION This fact sheet updates the Evapotranspiration Landfill Cover Systems Fact Sheet that was pub

lished in 2003. At that time evapotranspiration (ET) covers were more in a demonstration phase. Now they are increasingly being considered for use at waste disposal sites. These include municipal solid waste (MSW) landfills, hazard

ous waste (HW) landfills, and isolated arid waste sites when equivalent performance to conven

tional final cover systems can be demonstrated. Conventional cover system designs use barrier layers consisting of materials with low hydraulic conductivity (e.g., clay, geosynthetic clay liners, or geomembranes) to minimize the percolation of water from the cover to the waste. ET cover systems use water balance components to mini

mize percolation. These cover systems rely on

This fact sheet is intended solely to provide general information about evapotranspiration covers. It is not intended, nor can it be relied upon, to create any rights enforceable by any party in litigation with the United States. Use or mention of trade names does not constitute endorsement or recommendation for use.


### United States Office of Solid Waste and EPA 542-F-11-001 Environmental Protection Emergency Response February 2011 Agency (5203P) www.epa.gov www.cluin.org The alternative covers database contains 222 project profiles. These project profiles include site background information, cover type and construction details, status (pro

posed, complete, under construction), cost information, and contacts. Sources of in

formation include EPA and state websites, conference proceedings, studies, and indi

vidual contributions. Individuals wishing to have a cover they are familiar with listed can submit it online. The database is updat

ed as new information becomes available. Appendix A of this document contains a list of ET sites by EPA region and state. http://cluin.org/products/altcovers 

## TABLE OF CONTENTS

INTRODUCTION

......................................... 1 BACKGROUND

........................................... 2 DESCRIPTION

............................................ 3 LIMITATIONS

.............................................. 6 DESIGN CONSIDERATIONS

...................... 6 Climate

.................................................. 6 Soil Type

............................................... 7 Soil Thickness

....................................... 7 Vegetation Types

................................... 7 Soil Fertility

........................................... 8 Control Layers

....................................... 8 PERFORMANCE MONITORING

................ 8 Monitoring Systems

.............................. 9 Numerical Models

................................. 9 COST

........................................................ 10 TECHNOLOGY STATUS

........................... 11 REFERENCES

......................................... 11 GLOSSARY

............................................... 13 APPENDIX A: Proposed, Approved, and Installed Sites Having Evapotranspiration Covers

....................................................... 15 APPENDIX B: Data From Two Comparison Demonstration Projects

......... 24

### 2 soil properties (e.g., soil texture and associated soil water storage capacity) to store water until it is either transpired through vegetation or evapo

rated from the soil surface. The fact sheet provides a summary of ET tech

nical issues, including design considerations, performance monitoring, cost, technology status, and potential limitations on use. It is intended to provide basic information to site owners and operators, regulators, consulting engineers, and other interested parties about these potential design alternatives. Appendix A updates the 2003 list of ET cover sites by adding over 130 new full scale examples. A separate on-line database pro

vides more site specific information about these sites as well as other projects using ET covers. Additional sources of information are also provided in the project specific references in the database. The information contained in this fact sheet was obtained from currently available technical litera

ture and from discussions with site managers. It is not intended to serve as guidance for actual design or construction, nor is it intended to sug

gest that ET final cover systems should be used at any particular site. 1 

### The fact sheet does not address alternative materials for use in final cover systems, or other alternative cover system designs, such as asphalt covers. BACKGROUND Final cover systems often are used at landfills; abandoned dumps; some hazardous, low-level, and mixed low-level waste sites with conducive environmental conditions; hazardous waste con

tainment facilities; sites with surface contami

nation; and other types of waste disposal sites. There are a number of reasons for using them, including to control moisture and percolation, manage surface water runoff, minimize erosion, prevent direct exposure to waste, control gas emissions and odors, prevent occurrence of disease vectors and other nuisances, and meet aesthetic and other end-use purposes. Final cov

er systems are intended to remain in place and maintain their functions for periods of many

1 For example, EPA’s Superfund remedy selection decisions are made on a site-specific basis. Thus, final cover systems are evaluated in a manner consis

tent with the overall framework established for remedy selection under CERCLA, the National Oil and Haz

ardous Substances Pollution Contingency Plan, and associated Superfund program guidance. 

### decades to hundreds of years. Cover systems may be used alone or, if warranted, in conjunc

tion with other technologies (for example, slurry walls and groundwater pump and treat systems) to contain waste or leachate. The design of cover systems is site specific and depends on the intended function of the final cover–cover designs can range from a single layer of soil to a complex multi-layer system that includes synthetic materials. To minimize per

colation, conventional cover systems typically use low-conductivity barrier layers. These barrier layers are often constructed of compacted clay, geomembranes, geosynthetic clay liners, or com

binations of these materials. Depending on the material type and construction method, the satu

rated hydraulic conductivities for these barrier layers are typically between 1x10 -5

### and 1x10 -9

### centime

ters per second (cm/s). In addition, conventional cover systems generally include shallow-rooted plants and additional layers, such as surface layers to prevent erosion; protection layers to minimize freeze/thaw damage; internal drainage layers; and gas collection layers (Environmental Protection Agency [EPA] 1991; Hauser, Weand, and Gill 2001b). The design, construction, and maintenance of cover systems may be subject to statutory and regulatory requirements under various federal and state programs; some of these requirements also may come into play in cleanup programs. For example, with regard to municipal solid waste facilities, regulations under the Resource Conser

vation and Recovery Act (RCRA) for the design and construction of final cover systems are based on using a low-conductivity barrier layer (conven

tional cover system). Under RCRA Subtitle D (40 CFR 258.60), the minimum design requirements for final cover systems at municipal solid waste landfills (MSWLF) depend on the bottom liner system or the natural subsoils, if no liner system is present. The final cover system must have a permeability less than or equal to that of the bot

tom liner system (or natural subsoils) or a perme

ability no greater than 1x10 -5

### cm/s, whichever is less. This design requirement was established to minimize the “bathtub effect,” which occurs when the landfill fills with liquid because the cover system is more permeable than the bottom liner system. This bathtub effect greatly increases the potential for generation of leachate.

### 3 Until March 2004, the equivalent reduction lan

guage provided the statutory underpinning for proposing an alternative cover at an MSWLF. On March 22, 2004, 40 CFR 258 was amended to allow for research, development, and dem

onstration permits (40 CFR 258.4). These per

mits are issued for three years with up to three renewals (12 years total). The regulation states, “The director of an approved state may issue a research, development, and demonstration per

mit for a new MSWLF unit, existing MSWLF unit, or lateral expansion, for which the owner or operator proposes to utilize innovative and new methods which vary from the final cover crite

ria of §258.60(a)(1), (a)(2) and (b)(1), provided the MSWLF unit owner/operator demonstrates that the infiltration of liquid through the alterna

tive cover system will not cause contamination of groundwater or surface water, or cause leachate depth on the liner to exceed 30 cm.” Figure 1 shows the minimum recommended requirements for a typical conventional Subtitle D landfill which consist of a 6-inch soil erosion layer, a geomembrane (when the landfill has a geomembrane liner), and an 18-inch barrier layer of soil that is compacted to yield a saturated hydraulic conductivity equal to or less than 1x10 -5 

### cm/s (EPA 1992).

As another example, for hazardous waste landfills, RCRA Subtitle C (40 CFR 264 and 265) provides certain design specifications for final cover systems. These include the same provision for Subtitle D that the cover system have a permea

bility less than or equal to the permeability of any bottom liner system or natural subsoils present. To help implement these regulatory requirements, EPA has issued guidance for the minimum design of these final cover systems. Figure 1 shows an example of a RCRA Subtitle C cover at a hazard

ous waste landfill (EPA 1989). The design and construction requirements, as defined in the RCRA regulations, also may be applied under RCRA corrective action and other cleanup programs (e.g., Superfund or state cleanup programs). At Superfund remedial sites involving on-site disposal, the RCRA regulations for conventional covers usually are identified as applicable or relevant and appropriate require

ments (ARARs) for the site. 2

### Under RCRA, an alternative design, such as an ET cover, can be proposed in lieu of a RCRA design if it can be demonstrated that the alternative provides equivalent performance with respect to reduction in percolation and other criteria, such as erosion resistance and gas control. Examples of sites that have proposed, approved, or installed ET covers and the regulatory program they are operating under are given in Appendix A. Details on these sites can be found in the alter

native cover profiles database at http://cluin.org/ products/altcovers

. DESCRIPTION ET cover systems are designed to rely on the ability of a soil layer to store the precipitation until it is naturally evaporated or is transpired by the vegetative cover. In this respect they differ from more conventional cover designs in that they rely on obtaining an appropriate water storage capac

ity in the soil rather than an as-built engineered low hydraulic conductivity. ET cover system designs are based on using the hydrological processes (water balance components) at a site, which include the water storage capacity of the soil, precipitation, surface runoff, evapotranspi

ration, and infiltration. The greater the storage capacity and evapotranspirative properties are, the lower the potential for percolation through the cover system.

2In addition to compliance with ARARs, CERCLA Sec

tion 121 requires that remedial actions ensure protec

tiveness of human health and the environment. 

### Figure 1. Examples Subtitle D and C Cover Design. Source EPA 1992a and 1989

### 4 ET cover system designs tend to emphasize the following (Dwyer 2003; Hakonson 1997; Hauser, Weand and Gill 2001b):

• Fine-grained soils, such as silts and clayey silts, that have a relatively high water storage capacity

• Appropriate vegetation for long-term stability and evapotranspiration

• Locally available soils to streamline construc

tion and provide for cost savings Use of local soils allows the opportunity to utilize natural analogue data for speculating future per

formance. In addition to being called ET cover systems, these types of covers have also been referred to in the literature as water balance covers, alterna

tive earthen final covers, vegetative landfill covers, soil-plant covers, and store-and-release covers. ET cover systems are constructed using a mono

lithic soil barrier. Monolithic covers, also referred

**Exhibit 1.**Monolithic Cover at Lopez Canyon Sanitary Landfill Site type: Municipal solid waste landfill Scale: Full scale Cover design:The ET cover was installed in 1999 and consists of a 3-foot silty sand/clayey sand layer, which overlies a 2-foot foundation layer. The cover soil was placed in 18-inch lifts and compacted to 95 percent with a permeability of less than 3x10 -5

### cm/s. Native vegetation was planted, including arteme

sia, salvia, lupines, sugar bush, poppy, and grasses. In 2001, fifty 30-KW microturbines that use landfill gas as fuel were installed at the site. They provide sufficient electricity to power 1,500 homes. Regulatory status: In 1998, Lopez Canyon Sanitary Landfill received conditional approval for an ET cover, which required a minimum of two years of field performance data to validate the model used for the design. An analysis was conducted and provided the basis for final regulatory approval of the ET cover. The cover was fully approved in October 2002 by the California Regional Water Quality Control Board - Los Angeles Region. Performance data: Two moisture monitoring systems were installed, one at Disposal Area A and one at Disposal Area AB+ in May and November 1999, respectively. Each monitoring system has two stacks of time domain reflectometry probes that measure soil moisture at 24-inch intervals to a maximum depth of 78 inches, and a station for collecting weather data. Based on nearly 3 years of data, there is gener

ally less than a 5 percent change in the relative volumetric moisture content at the bottom of the cover compared to nearly 90 percent change near the surface. This implies that most of the water infiltrating the cover is being removed via evapotranspiration and is not reaching the bottom of the cover. Modeling: The numerical model UNSAT-H was used to predict the annual and cumulative percolation through the cover. The model was calibrated with 12 months of soil moisture content and weather data. Following calibration, UNSAT-H predicted a cumulative percolation of 50 cm for the ET cover and 95 cm for a conventional cover over a 10-year period. The model predicted an annual percolation of approximately 0 cm for both covers during the first year. During years 3 through 10 of the simulation, the model predicted less annual percolation for the ET cover than for the conventional cover. Maintenance activities:During the first 18 months, irrigation was conducted to help establish the veg

etation. Once or twice a year, brush is cleared to comply with Fire Department regulations. Prior to the rainy season, an inspection is conducted to check and clear debris basins and deck inlets. No mowing activities or fertilizer applications have been conducted or are planned. Cost: Initial costs were estimated at $4.5 million, which includes soil importation, revegetation, quality control and assurance, construction management, and installation and operation of moisture monitoring systems. Sources: City of Los Angeles 2003, Hadj-Hamou and Kavazanjian 2003. More information available at http://cluin.org/products/altcovers

### 5 to as monofill covers, use a single fine-grained soil layer to retain water and support the vegeta

tive community (Albright et al. 2010 and Hauser 2009). Figure 2 shows an example of a mono

lithic ET cover. Exhibit 1 provides an example of a full-scale monolithic cover at a MSW landfill. A monolithic cover design can be modified by adding a capillary break. This entails placing a coarser grained material, usually a sand or gravel, under the monolithic fine-grained soil, as shown conceptually in Figure 3. The differences in the unsaturated hydraulic properties (i.e., soil matric potential) between the two layers minimize percolation into the coarser grained (lower) layer under unsaturated conditions (Stormont 1997). The finer-grained layer has the same function as the monolithic soil layer; that is, it stores water until it is removed from the soil by evaporation or transpiration mechanisms. The discontinuity in pore sizes between the coarser-grained and finer-grained layers forms a capillary break at the interface of the two layers. The break results in the wicking of water into unsaturated pore spacein the finer grained soil, which allows the finergrained layer to retain more water than a mono

lithic cover system of equal thickness. Capillary forces hold the water in the finer-grained layer until the soil near the interface approaches sat

uration. If saturation of the finer-grained layer 

### Vegetation Fine-grained Layer

Interim Cover

Waste
**Figure 2.** Conceptual Design of a Monolithic ET Cover Vegetation Fine-grained Layer
Coarse-grained Layer Interim Cover
Waste


### Figure 3. Conceptual Design of a Capillary Barrier ET Cover

**Exhibit 2.**Capillary Barrier ET Cover at Rocky Mountain Arsenal Superfund Site Site type: Consolidation area covers Scale:Full scale Cover design:These RCRA Subtitle C equivalent ET covers have been constructed for former waste disposal basins and manufacturing process areas that were contaminated during pesticide production. The design consists of a minimum of 16 inches of crushed concrete placed as a biota barrier, followed by a capillary barrier layer of pea gravel that provides a capillary break. The surface soil layer consists of at least 4 feet of soil seeded with a mix of cool and warm season native vegetation. Modeling:Construction parameters were developed using data from a four year RCRA equivalent dem

onstration study. The modeling was done using UNSAT-H. Maintenance activities: Construction began in 2007 and finished in 2009. The covers are currently being monitored and maintained. Performance:The ET cover performance is monitored using a number of pan lysimeters (30 feet x 50 feet) which have shown that the cover is performing as expected. Cost:According to the responsible party, the total cost of constructing the ET covers was $69 million, and they cover approximately 450 acres. Sources:Rocky Mountain Arsenal cleanup site: http://www.rma.army.mil/ ; and EPA Region 8 Superfund site: http://www.epa.gov/region8/superfund/co/rkymtnarsenal/index.html

.

### 6 occurs, the water will move relatively quickly into and through the coarser-grained layer and to the waste below (Albright et al. 2010, Hauser 2009, and ITRC 2003). Exhibit 2 provides an example of a capillary barrier at a Rocky Mountain Arsenal hazardous waste site. In addition to being potentially less costly to con

struct, ET covers have the potential to provide equal or superior performance compared to conventional cover systems, especially in arid and semi-arid environments (generally accepted as areas hav

ing less than 10 and 20 inches of precipitation, respectively). In these environments, they may be less prone to deterioration from desiccation, cracking, and freezing/thawing cycles. ET covers also may be able to minimize side slope instability, because they do not contain geomembrane layers, which can cause slippage (Albright and Benson 2005, Benson et al. 2002; Dwyer et al. 1999). LIMITATIONS Although they have been approved in humid climates (e.g., Marine Corps Logistics Station Albany, GA and General Electric, Schenectady, NY), ET cover systems are generally consideredmore applicable in areas that have arid or semiarid climates like those found in parts of the Great Plains and West (e.g., North and South Dakota, Montana, Idaho, eastern Washington and Ore

gon, Utah, Colorado, West Texas, New Mexico, Arizona, Nevada, and southern California). Albright and Benson (2005) in their examination of data generated in EPA’s Alternative Cover Assessment Program (ACAP) found: “In humid locations with the abundant precipitation and typically lower potential evapotranspiration, the store-and-release mechanism used by ET cov

ers does not provide sufficient hydraulic control to match the performance of conventional com

posite covers .” (emphasis added) However, the ACAP field data did show that in humid locations properly designed ET covers can provide perfor

mance comparable to that of the compacted clay covers in those locations. In addition, site specific conditions, such as site location (e.g., appropriate soil) and landfill char

acteristics, may limit the use or effectiveness of ET cover systems. Local climatic conditions (amount, seasonal distribution, and form of pre

cipitation) also can limit the effectiveness of an ET cover at a given site. For example, snow often melts when vegetation is dormant, and with

out sufficient water storage capacity unaccept

able percolation might occur (EPA 2000; Hauser, Weand, and Gill 2001b). However, if technically and financially feasible, this might be mitigated by thickening the ET layer. Two federal research programs, the Department of Energy (DOE) sponsored Alternative Land

fill Cover Demonstration (ALCD) and the ACAP, provide the best collection of data to describe the performance of ET cover systems in terms of minimizing percolation. Hauser (2009) also has some additional performance information; how

ever, there are limited data on the ET covers’ abil

ity to minimize erosion, resist biointrusion, and retain long-term effectiveness. On the other hand, erosion, effectiveness of biobarriers, and mainte

nance of vegetative cover over extended periods of time are issues faced by all conventional cov

ers, and those design aspects are similar to ET covers. While the principles of ET covers and their corresponding soil properties have been under

stood for many years, their application as final cover systems for landfills has emerged only since the mid-1990s. Regulators in southern California initially required any landfill operator who wanted to deploy an ET cover to set up a demonstration project to prove equivalency. The success of these demonstrations has led to the regulators allowing an ET cover if the landfill owner shows that soil, design, and climatic conditions are similar to those of a landfill facility with a permitted ET cover. DESIGN CONSIDERATIONS The design of ET cover systems is based on providing sufficient water storage capacity and evapotranspiration to control moisture and water percolation into the underlying waste. The follow

ing considerations generally are involved in the design of ET covers. Climate The amount, form, and distribution of precipita

tion over a year, combined with factors that influ

ence potential evapotranspiration, determine the total amount of water storage capacity needed for the cover system. This information can usually be found at nearby weather stations. The cover may need to accommodate a spring snowmelt event that causes the amount of water at the cover to be relatively high for a short period of time or con

-

### 7 ditions during cool winter weather with persistent, light precipitation. Storage capacity is particularly important if the event occurs when local vegeta

tion is dormant, resulting in little or no transpira

tion. Other factors related to climate that are im

portant to cover design are temperature, wind, and relative humidity (Benson 2001; EPA 2000; Hauser, Weand, and Gill 2001b). Soil Type Finer-grained materials, such as silts and clayey silts, are typically used for ET cover systems be

cause they have a greater storage capacity than sandy soils. Sandy soils are typically used for the bottom layer of the ET capillary barrier cover sys

tem to provide a contrast in unsaturated hydrau

lic properties between the two layers. Many ET covers are constructed of soils that include clay loam, silty loam, silty sand, and sandy loam. The storage capacity of the soil varies among differ

ent soil types and requires laboratory analysis to quantify. One key aspect of construction is avoid

ing over-compaction (greater than 80-90%) dur

ing placement. Higher bulk densities from overcompaction may reduce the storage capacity of the soil and inhibit growth of roots (Chadwick et al. 1999; Hauser et al. 2001). Soil Thickness The thickness of the soil layer(s) depends on the required storage capacity, which is determined by the water balance at the site. The soil layers need to accommodate the design climate conditions, such as snowmelts and summer thunderstorms, or periods of time during which ET rates are low and plants are dormant. Monolithic ET covers have been constructed with soil layers ranging from 2 feet to 10 feet. Capillary barrier ET covers have been constructed with finer-grained lay

ers ranging from 1.5 feet to 5 feet, and coarsergrained layers ranging from 0.5 feet to 2 feet. In some arid to semiarid areas, when there is a lack of local precipitation data, the potential performance of an ET cover might be estimated by natural analog. This is done by trenching and examining the trench walls for a caliche layer. Caliche (CaCO 3 

### ) is a precipitation product and when shallow generally indicates the level of deepest recent percolation. Also, an accumula

tion of soluble ions such as chloride can indicate the depth of recent percolation. Vegetation Types Vegetation for the cover system is used to pro

mote transpiration and minimize erosion by stabi

lizing the surface of the cover. It can also be used for aesthetics or to promote habitat. Grasses, shrubs, and trees have all been used on ET cov

ers. A mixture of native plants generally is planted, though not always, because native vegetation usually is more tolerant than imported vegetation to regional conditions, such as extreme weatherand disease. A combination of warm- and coolseason species should provide water uptake throughout the entire growing season, which enhances transpiration. In addition, native veg

etation species are less likely to disturb the natural ecosystem (Dwyer et al. 1999; EPA 2000). If deep rooting vegetation is considered for the cover, the designer should consider whether root penetration into the waste area will result in any transport of constituents into the above ground biomass. The presence of constituents such as heavy metals or radionuclides in leaf and stem tissue could present a hazard. Summary of Key Design Considerations

• Climate—amount, form and timing of precipitation determines storage capac

ity need

• Soil Type—finer grained soils are pre

ferred for fertility and storage capacity

• Soil Thickness—combined with soil type determines storage capacity of cover

• Vegetation Types—must be appropriate for location with well developed root systems to promote transpiration and provide long-term performance

• Soil Fertility—to sustain vegetation when plants are used

• Control Layers—biobarriers, gas collec

tion, and drainage layers are used as needed

### 8 Finally, consideration needs to be given to how long the selected vegetation will take to establish itself and how this will affect the cover’s performance. Soil Fertility When vegetation is a component of an ET cover system, the evaluation of the soil that is proposed for the cover (not the subgrade) should include a determination of whether the pH, cation exchange capacity, organic matter, and nitrogen, phospho

rus, potassium, and micronutrient content are appropriate for the vegetation proposed for use on the cover (ITRC 2003b, Albright et al. 2010). Amendments, such as lime, biosolids, sawdust, or synthetic conditioners, can be worked into the soil to improve its suitability for planting and/or water storage capacity. These types of amend

ments, while adding to the cover construction cost, tend to be long-lived and should not need to be repeated. Fertilizers and amendments, such as manure, can be added at initial planting to helpestablish the cover; however, they are not longlived and must be reapplied in nutrient-poor soils on a regular basis. The need for reapplication of fertilizers will present an ongoing cost to the proj

ect and should be carefully evaluated in selecting an ET cover over a conventional cover. While it is not necessary that borrow soils be obtained on

site or locally, the cost of transporting them any distance should be considered (e.g., it could be prohibitively expensive). For a more complete discussion, see Section 5.2 Preconstruction Cov

er Material Specifications of ITRC 2003b. Control Layers Control layers, such as those used to minimize animal intrusion, promote drainage, and control and collect landfill gas, are often included for conventional cover systems and may also be in

corporated into ET cover system designs. For ex

ample, a capillary barrier ET cover for the mixed waste landfill at Sandia National Laboratories in New Mexico has a one-foot-thick crushed rock biobarrier located beneath the soil cover (about four feet bgs) to prevent animals from burrowing into the waste layer. Because of the difference in size between the soil and the rock, the rock layer also acts as a capillary break. At another site, Monticello Uranium Mill Tailings Site in Utah, an ET capillary barrier design has a cobble layer as an animal intrusion barrier located within the fine soil layer and above the 12-inch thick capil

lary barrier layer. PERFORMANCE MONITORING Protection of groundwater quality often is a pri

mary performance goal for all waste containment systems, including final cover systems. The potential adverse impact to groundwater quality can result from the release of leachate generated in landfills or other closed in-place waste disposal units such as unlined surface impoundments. The rate of leachate generation (and potential impact on groundwater) can be minimized by keeping liquids out of a landfill or contaminated source area of a remediation site. As a result, the function of minimizing percolation typically becomes a key performance criterion for a final cover system (EPA 1991). Monitoring the performance of ET cover systems has generally focused on evaluating the ability of these designs to minimize water drainage into the waste. Percolation performance typically is reported as a flux rate (inches or millimeters of water that have migrated downward through the base of the cover in a period of time, generally considered as 1 year). Percolation monitoring for ET cover systems is measured directly using pan lysimeters or estimated indirectly using soil moisture measurements and soil matric potential, thereby allowing the calculation of a flux rate. A more detailed summary on the advantages and disadvantages of both approaches can be found in Benson et al. (2001) and EPA (2004). Percolation monitoring can also be evaluated indirectly by using leachate collection and removal systems. For landfills underlain with these sys

tems, the amount and composition of leachate generated can be used as an indicator of the performance of a cover system (the higher the percolation, the more leachate that will be gener

ated) (EPA 1991). Although the ability to minimize percolation is a performance criterion for final cover systems, limited data are available about percolation per

formance for final cover systems for both conven

tional and alternative designs. Most of the recent readily available data on flux rates have been generated by the ACAP and ALCD programs; see Appendix B for discussion and data presentation. From these programs, flux rate performance dataare available for 14 sites with demonstrationscale ET cover systems (Dwyer 2003, Albright and Benson 2005).

### 9 Additional demonstration projects of ET cov

ers conducted in the 1980s and early 1990s are discussed in the ACAP Phase I Report, which is available at http://www.dri.edu/acap-research

. Monitoring Systems Direct measurement of water flowing through the bottom of a cover can be done using a pan ly

simeter. The lysimeters are installed underneath the cover system, typically as geomembrane lin

ers backfilled with a drainage layer and shaped to collect water percolation. Water collected in the lysimeter is directed toward a monitoring point and measured using a variety of devices (for ex

ample, tipping bucket, pressure transducers). Pan lysimeters were used in the ALCD and ACAP programs for collecting performance data for ET cover systems and are part of the design for the Rocky Mountain Arsenal cover systems. They are the monitoring system of choice for equivalency demonstrations. Details of the ACAP lysimeters are in Albright et al. (2004). Soil moisture monitoring can be used to deter

mine moisture content at discrete locations in cover systems and to evaluate changes over time in horizontal or vertical gradients. Soil water prop

erties are measured using a variety of methods and include methods for determining soil mois

ture (TDR, neutron attenuation, and resistivity), soil humidity (psychrometer), and soil matric po

tential (heat dissipation units or HDUs). Table 1 presents examples of non-destructive techniques that have been used to assess soil moisture content of ET cover systems. A high soil mois

ture value indicates that the water content of the cover system is approaching its storage capacity, thereby increasing the potential for percolation. Soil moisture is especially important for capillary barrier ET cover systems; when the finer grained layer becomes saturated, the capillary barrier can fail resulting in water percolating through the highly permeable layer to the waste below (Ha

konson 1997). Monitoring instruments have vari

ous configurations, costs, and accuracies. The choice of which one to use would depend on the site data quality objective. Maintaining the effectiveness of the cover system for an extended period of time is another impor

tant performance criterion for ET covers as well as conventional covers. Some factors to con

sider in evaluating short-term and long-term per

formance monitoring of a final cover system in

clude settlement effects, gas emissions, erosion or slope failure, and maintenance of vegetative cover. These factors can be monitored using a variety of methods including settlement gauges, erosion pins, TDR cables for subsidence, soil gas wells and associated sampling ports, and remote sensing (e.g., LIDAR). Numerical Models Models can be used to support the design of ET covers. Although models have strengths and weaknesses and none can accurately predict cover behavior in all environments, in their sim

plest application, a model can be used to test the assumptions made in the designer’s conceptual model. A good example of this is where model sim

ulation shows a cover thickness that is clearly too thin or shows diminishing returns in adding more soil beyond an optimum thickness to achieve water storage capacity. Simulations by several models to test the conceptual model and design can be very useful in identifying critical assump

tions where a small change can result in large performance deviations. Identifying sensitive as

sumptions allows for more conservative design specifications or the application of greater quality control checks. If such a procedure is desirable, a model using Richards’ equation (ITRC 2003b) is necessary to properly simulate the mechanisms important to cover function. At sites where ET en

gineered barriers are expected to last hundreds or thousands of years (e.g., DOE low-level radio

active burial grounds), the modeling should in

clude extreme weather events and their resultant affects on engineered barrier design. A number of models have been used for estimat

ing water balances. Research reviewed for this fact sheet suggests that opinions differ among practitioners about how successful a given model will be in predicting cover performance. A mod

el should only be selected after examining its strengths and weaknesses in simulating site-spe

cific conditions. For example, if early snowmelt is a critical factor, how well does the model simu

late it? For design purposes it might be prudent, though somewhat more expensive, to use two models, such as a water balance and a numeri

cal model, to estimate cover performance (Khire et al. 1997). Table 2 in Chapter 3 of Albright et al. (2002) compares the processes and attributes of 10 models.

### 10 COST Despite the large number of projects installed to date, limited cost data are available for the con

struction and operation and maintenance of ET cover systems. The available construction cost data indicate that these cover systems have the potential to be less expensive to construct than conventional cover systems, especially those requiring geomembranes. Factors affecting the cost of construction include soil layer thickness, availability of materials, placement methods, and The numerical model HELP is a widely used waterbalance model that is most appropriate for nonET landfill cover design. UNSAT-H, VADOSE/W and HYDRUS-1D/2D/3D are examples of numer

ical models that have been used frequently for the design of ET covers. Some models are in the public domain, others require purchase. Hauser (2009) recommends using the water balance Erosion Productivity Impact Calculator (EPIC), which is in the public domain, for ET cover mod

eling. EPIC is a water balance model and does not use Richards equation.

Table 1. Examples of Non-Destructive Soil Moisture Monitoring Methods Method Description Instrumentation Capacitance sensor Uses frequency domain induced polariza

tion to measure the dielectric properties of the soil. The dielectric of dry soil is ap

proximately 5, and the dielectric of water is approximately 80. When soil becomes moistened by water, its dielectric increases. Consists of a probe connected to a coaxial cable and buried at appropriate depth

Electrical resistance blocks Measures resistance resulting from a gradi

ent between the sensor and the soil; higher resistance indicates lower soil moisture Consists of electrodes embedded in a gypsum, nylon, or fiberglass porous material Gee lysimeter Wicks water from soil around a collection container and measures the resulting water level in the container directly Consists of a small collector body and a wick. The water level in the collector body is measured by an electronic water level gauge. Thermal dissipation unit Uses a heated ceramic block to determine soil moisture near the block. The rate of heat dissipation from the block is related to soil moisture—the quicker the dissipation the higher the soil moisture. Consists of a small heater inside a porous block with a temperature sensor attached by cable to a surface meter

Neutron attenuation Emits high-energy neutrons into the soil that collide with hydrogen atoms associated with soil water and counts the number of pulses, which is correlated to moisture content Consists of a probe inserted into access boreholes with aluminum or polyvinyl chloride casing
Psychrometer Measures relative humidity (soil moisture) within a soil Generally consists of a thermo

couple, a reference electrode, a heat sink, a porous ceramic bulb or wire mesh screen, and a recorder Suction lysimeter Collects pore (unsaturated) water directly Constructed of a porous ceramic bulb with a cylindrical reservoir to store water. A tube to the surface allows water to be drawn and measured. Tensiometer Measures the matric potential of a given soil, which is converted to soil moisture content Commonly consists of a porous ceramic cup
Time domain reflectrometry Sends pulses through a cable and observes the reflected waveform, which is correlated to soil moisture Consists of a cable tester (or specifically designed commercial time domain reflectrometry unit), coaxial cable, and a stainless steel probe

### 11 project scale. Locally available soils are typically used for ET cover systems. In addition, the use of local materials generally minimizes transporta

tion costs (Dwyer 2003, EPA 2000). Also, when comparing the costs for ET and conventional covers, it is important to consider the types of components for each cover and their intended function. For example, it would generally not be appropriate to compare the costs for a conven

tional cover with a gas collection layer to an ET cover with no such layer. Additional information about the costs for specific ET cover systems is provided in some of the project profiles discussed under Technology Status. TECHNOLOGY STATUS EPA has developed and recently updated a searchable on-line database with information about ET cover systems, available at http://cluin. org/products/altcovers . As of February 2011, the database contained 167 projects with full scale monolithic ET cover systems and 5 projects with capillary barrier ET cover systems; these sys

tems have been proposed, tested, or installed throughout the United States. Full scale appli

cations have primarily been in the Great Plains and western states. Where data are available, the database provides project profiles that in

clude site background information (such as site type, climate, hydrogeology), project information (such as purpose, scale, status), cover informa

tion (such as design, vegetation, installation), per

formance and cost information, points of contact, and references. Appendix A provides a summary of key information from the database for projects with monolithic ET or capillary barrier ET covers. In addition to this on-line database, several fed

eral and state programs have demonstrated and assessed the performance of ET cover systems. The following programs provide performance data, reports, and other useful information to help evaluate the applicability of ET designs for final cover systems.

• Alternative Landfill Cover Demonstration: See Exhibit 3 in Appendix B for more infor

mation or http://www.sandia.gov/Subsurface/ factshts/ert/alcd.pdf

.

• Alternative Cover Assessment Program: See Exhibit 4 in Appendix B for more information or http://www.dri.edu/acap-research

. • Interstate Technology and Regulatory Council published two reports on ET covers: Technol

ogy Overview Using Case Studies of Alter

native Landfill Technologies and Associated Regulatory Topics and Technical and Regu

latory Guidance for Design, Installation, and Monitoring of Alternative Final Landfill Cov

ers . For further information, see http://www. itrcweb.org/guidancedocument.asp?TID=21

. In the initial stages of its program, California re

quired any landfill that desired to employ an ET cover to conduct a demonstration project. The success of these demonstrations has led to the regulators allowing an ET cover if the landfill owner shows soil, design, and climatic condi

tions are similar to those of a landfill facility with a permitted ET cover. Texas has a similar pro

gram. Both of these states have seen a signifi

cant increase in the number of landfills using or proposing ET covers. REFERENCES Abichou, T., X. Liu, and K. Tawfiq. 2004. Design of Cost Effective Lysimeters for Alternative Land

fill Cover Demonstrations Projects, Report #04- 0232007. Florida State University, College of En

gineering. 88 pp. Albright, W., G. Gee, G. Wilson, and M. Fayer. 2002. Alternative Cover Assessment Project Phase I Report, Publication No. 41183. Desert Research Institute, NV. 203 pp. Albright, W., C. Benson, G. Gee, A. Roesler, T. Abichou, P. Apiwantragoon, B. Lyles, and S. Rock, 2004, “Field Water Balance of Landfill Final Covers.” J. of Environmental Quality, 33;2317- 2332. Albright, W. and C. Benson. 2005. Alternative Cover Assessment Program: Report to Office of Research and Development National Risk Man

agement Research Lab Land Remediation and Pollution Control Division. Desert Research Insti

tute and University of Wisconsin, 54 pp. Albright, W., W. Waugh, and C. Benson. 2007. Enhancements to Natural Attenuation: Selected Case Studies, Washington Savannah River Com

pany, WSRC-STI-2007-00250, p 9-30.

### 12 Hadj-Hamou, T. and E. Kavazanjian, Jr. 2003. “Monitoring and Evaluation of Evapotranspirative Cover Performance.” Proceedings of the 9th International Waste Management and Landfill Symposium, Sardinia, Italy, 6-10 October. Hakonson, T.E. 1997. “Capping as an Alternative for Landfill Closures-Perspectives and Ap

proaches.” Environmental Science and Research Foundation. Proceedings, Landfill Capping in the Semi-Arid West: Problems, Perspectives, and Solutions. Grand Teton National Park, Wyoming. May 21-22. ESRF-019. p 1-18. Hakonson, T., et al. 1994. Hydrologic Evaluation of Four Landfill Cover Designs at Hill Air Force Base, Utah. Los Alamos National Laboratory, Los Alamos, New Mexico. LAUR-93- 4469. Hauser, V.L., and B.L. Weand. 1998. “Natural Landfill Covers.” Proceedings, Third Tri-Service Environmental Technology Workshop. San Diego, California. August 18-20. Hauser, V.L., B.L. Weand, and M.D. Gill. 2001a. “Natural Covers for Landfills and Buried Waste.” Journal of Environmental Engineering. Sept. p 768-775. Hauser, V., B. Weand, and M. Gill. 2001b. Alter

native Landfill Covers. Air Force Center for Envi

ronmental Excellence. 38 pp. Hauser, Victor L. 2009. Evapotranspiration Cov

ers for Landfills and Waste Sites. CRC Press, Boca Raton, FL. ISBN: 13: 978-1-4200-8651-5, 203 pp. ITRC. 2003a. Technology Overview Using Case Studies of Alternative Landfill Technologies and Associated Regulatory Topics. 107 pp. ITRC. 2003b. Technical and Regulatory Guid

ance for Design, Installation, and Monitoring of Alternative Final Landfill Covers. 198 pp. Kelln, C.J., S.L. Barbour, A. Elshorbagy, and C. Qualizza. 2006. “Long-Term Performance of a Reclamation Cover: The Evolution of Hydraulic Properties and Hydrologic Response.” Unsatu

rated Soils 2006: Proceedings of the 4th Inter

national Conference on Unsaturated Soils, 2-6 April 2006, Carefree, Arizona. ASCE, Reston, VA. Geotechnical Special Publication No. 147, ISBN: 0784408025. Albright, William H., Craig H. Benson, and W. Joseph Waugh, 2010. Water Balance Covers for Waste Containment Principles and Practice, ASCE Press, 158 pp. Benson, C.H. 2001. “Alternative Earthen Final Covers (AEFCs) or ‘ET’ Caps.” GEO Institute. Proceedings, Liners and Covers for Waste Con

tainment Facilities. Atlanta, Georgia. November 14-16. Benson, C.H. et al. 2001. “Field Evaluation of Alternative Earthen Final Covers.” International Journal of Phytoremediation. Volume 3, Number 1, p 105-127. Benson, C.H. et al. 2002. “Evaluation of Final Cover Performance: Field Data from the Alterna

tive Landfill Cover Assessment Program (ACAP).” Proceedings, WM 2002 Conference. Tucson, Ari

zona. February 24-28. Benson, C.H., A. Sawangsuriya, B. Trzebiatowski, and W.H. Albright 2007. “Postconstruction Changes in the Hydraulic Properties of Water Balance Cover Soils.” Journal of Geotechnical and Geoenviron

mental Engineering 133(4):349-359. Bolen, M.M. et al. 2001. Alternative Cover Assess

ment Program: Phase II Report. University of Wisconsin-Madison. Madison, Wisconsin. Sep

tember. Geo Engineering Report 01-10. Chadwick, Jr., D. et al. 1999. “Field Test of Poten

tial RCRA-Equivalent Covers at the Rocky Moun

tain Arsenal, Colorado.” Solid Waste Association Proceedings, North America’s 4th Annual Land

fill Symposium. Denver, Colorado. June 28-30. GR-LM 0004, p 21-33. City of Los Angeles. 2003. Personal commu

nication regarding Lopez Canyon Landfill from Doug Walters, Sanitary Engineer, Department of Public Works, to Kelly Madalinski, EPA. Septem

ber 25. Dwyer, S. 2003. Water Balance Measurements and Computer Simulations of Landfill Covers. University of New Mexico, Civil Engineering De

partment. May. Dwyer, S.F., J.C. Stormont, and C.E. Anderson. 1999. Mixed Waste Landfill Design Report. Sandia National Laboratories. SAND99-2514. October.

### 13 Kelsey, J.A., J.T. Kay, M. Ankeny, and M. Plummer. 2006. “Darcian Flux Estimations in Evapotranspi

ration Landfill Covers.” Unsaturated Soils 2006: Proceedings of the 4th International Conference on Unsaturated Soils, 2-6 April 2006, Carefree, Arizona. ASCE, Reston, VA. Geotechnical Spe

cial Publication No. 147, ISBN: 0784408025. Khire, M.V., C.H. Benson, and P.J. Bosscher. 1997. “Water Balance Modeling of Earthen Final Covers.” Journal of Geotechnical and Geoenvi

ronmental Engineering. August, p 744- 754. McGuire, P.E., J.A. England, and B.J. Andraski. 2001. “An Evapotranspiration Cover for Contain

ment at a Semiarid Landfill Site.” Florida State University. Proceedings, 2001 International Containment & Remediation Technology Confer

ence. Orlando, Florida. June 10 - 13. Mitchell, M. 2009. Mixed Waste Landfill Quarterly Progress Report Evapotranspirative Cover Con

struction Project, August - October 2009. Sandia National Laboratories, 38 pp. Roesler, A.C., C.H. Benson, and W.H. Albright. 2002. Field Hydrology and Model Predictions for Final Covers in the Alternative Cover Assessment Program-2002. University of Wisconsin-Madison. Geo Engineering Report No. 02-08. September 20, 279 pp. Scanlon, B.R., et al. 2002. “Intercode Compari

sons for Simulating Water Balance of Surficial Sediments in Semiarid Regions.” Water Resources Research. Volume 38, Number 12 Scanlon, B., R. Reedy, K. Keese, and S. Dwyer. 2005. “Evaluation of Evapotranspirative Cov

ers for Waste Containment in Arid and Semiarid Regions in the Southwestern US.” Vadose Zone Journal, 4, p. 55-71. Stormont, John C. 1997. “Incorporating Capillary Barriers in Surface Cover Systems.” Environmental Science and Research Foundation. Proceedings, Landfill Capping in the Semi-Arid West: Prob

lems, Perspectives, and Solutions. Grand Teton National Park, Wyoming. May 21 through 22. ESRF-019, p 39-51. EPA. 1989. Technical Guidance Document: Final Covers on Hazardous Waste Landfills and Sur

face Impoundments. EPA/530-SW-89-047. July. EPA. 1991. Seminar Publication, Design and Construction of RCRA/CERCLA Final Covers. EPA/625/4-91/025. May. EPA 1992a. Seminars: Design, Operation, and Closure of Municipal Solid Waste Landfills. EPA/600/K-92/002 EPA. 1992b. Subtitle D Clarification. 40 CFR 257 & 258. Federal Register pages 28626 through 28632. June. EPA. 2000. Introduction to Phytoremediation. Office of Research and Development. Washington, DC. EPA/600/R-99/107. February. EPA. 2004. Survey of Technologies for Monitor

ing Containment Liners and Covers, EPA 542-R04-013, 64 pp. Weand, B.L. et al. 1999. “Landfill Covers for Use at Air Force Installations.” AFCEE. Brooks Air Force Base, Texas. February.

NOTICE Preparation of this fact sheet has been funded wholly by the U.S. Environmental Protection Agency under Contract Num

ber EP-W-07-037. For more information regarding this fact sheet, please con

tact Steve Rock at (513) 569-7149 or roc k.steven@epa.govor Linda Fiedler at (703) 603-7194 or fiedler.linda@epa.gov

. This fact sheet is available for viewing or downloading from EPA’s Hazardous Waste Cleanup Information (CLU-IN) web site at http://cluin.org

.

### 14 GLOSSARY Arid and semi arid climates.In 1953, Peveril Meigs divided desert regions on Earth into three categories according to the amount of precipita

tion they received. In this now widely accepted system, extremely arid lands have at least 12 con

secutive months without rainfall, arid lands have less than 250 millimeters of annual rainfall, and semiarid lands have a mean annual precipitation of between 250 and 500 millimeters. Arid and extremely arid land are deserts, and semiarid grasslands generally are referred to as steppes. (USGS webpage http://pubs.usgs.gov/gip/deserts/ what/) Caliche. A subsurface carbonate horizon formed in a soil in an arid to semiarid region under condi

tions of low rainfall. The leaching of carbonates from the upper soil by precipitation combined with its limited downward percolation results in an accumulation of carbonates that form an often hard carbonate horizon and designate the deep

est penetration of the precipitation. Composite cover. A landfill cover that includes a synthetic layer such as a geomembrane. Dump.An area where illegal waste disposal has occurred. Evapotranspiration.The combination of water lost from the soil through direct evaporation and water lost to the atmosphere through plant tran

spiration. Geosynthetic clay liner. A woven fabric that encases a clay material, generally a smectite clay, to provide a low permeability layer. Hydraulic conductivity.In hydrology, a numeric coefficient describing the rate that water can move through a porous media. Usually expressed in cm/sec. Infiltration. The movement of water from the soil surface into the soil. Natural analog.A subsurface feature that occurs naturally that can be used to evaluate a similar engineered feature. In ET design the presence of a near surface caliche layer or chloride ion accu

mulation gives an indication of how deep precipi

tation is percolating in the subsurface. Percolation. The movement of water through soil. Permeability. The capacity of a porous media to transmit a fluid. Richards equation.A numerical representation of unsaturated flow of a fluid through porous media.
Water balance.In the context of a landfill cover, the evaluation of the end fate of precipitation; that is, percent run-off, infiltration, evaporation, tran

spiration, and percolation. Store and release.In the context of an ET cover, the cover soil will store precipitation (i.e., prevent its drainage into the underlying waste), until the water either evaporates or is transpired by the vegetative cover.

### 15 

# APPENDIX A PROPOSED, APPROVED, AND IN STALLED S ITES HAVING EVAPOTRANSPIRATION COVERS

### 16 This table is a list by region and state of sites that have proposed, approved, or installed ET covers. It also contains sites that had demonstration scale pilots, which may or may not have gone on to full scale. Proposed covers include sites where an ET cover has been proposed by the facility and approved by the governing agency (e.g., California) or has been proposed by the facility but approval is pending (e.g., Texas). In Texas the proposal is generally to amend an existing permit to add ET covers as an option. The state of Oklahoma provided a list of landfills that had approved and installed ET covers as did the states of Colorado and Montana. The state of Arizona provided electronic copies of the permits of facilities that had approved or installed ET covers. The California Regional Water Control Boards maintain electronic copies of their permits on their webpages as does the state of Utah. Sites were excluded from the list if the permit specifically called for a water infiltration barrier layer even though the permit referred to the cover as an ET cover. A legend and list of definitions is found at the end of the table.

Site Program Type of Site Scale Status Type of Cover Region 1 Region 2 New York GE Main Plant, Schenectady, NY RCRA HWS F Installed M State-Licensed Radioactive Waste Disposal Area, West Valley, NY NRC Rad Demo Complete BE
Region 3 Maryland Beltsville Agricultural Research Center (USDA), Beltsville, MD NRC Rad Demo Complete BE
College Park Landfill, College Park, MD CERCLA MSW Demo Complete M College Park Landfill, College Park, MD CERCLA MSW F Proposed M Pennsylvania Welsh Road Landfill, Honeybrook, PA CERCLA MSW F Installed M Region 4 Georgia Marine Logistics Base Albany Georgia ACAP MSW Demo Complete M Marine Logistics Base Albany Georgia CERCLA MSW F Installed M Region 5 Illinois Sheffield City Landfill, Sheffield, IL NRC Rad Demo Complete CB Michigan Casting Sand Landfill, Detroit, MI RCRA IW Demo Complete M Wisconsin Omega Hills, Milwaukee, WI RCRA MSW Demo Complete CB Region 6 New Mexico Cerro Colorado Landfill, Albuquerque, NM RCRA MSW F Proposed M Chemical Waste Landfill at Sandia National Laboratories, Albuquerque, NM RCRA HWS F Installed M
Crouch Mesa Landfill, Farmington, NM RCRA MSW F Proposed M Kirtland Air Force Base, Albuquerque, NM RCRA HW F Installed M 

### Evapotranspiration Covers

### 17 Site Program Type of Site Scale Status Type of Cover Los Alamos National Laboratory, Los Alamos, NM DOE Research Rad Demo Complete CB Mixed Waste Landfill at Sandia National Laboratories, Albuquerque, NM RCRA MW F Installed M
Molycorp Tailings Facility, Questa, NM CERCLA HWS F Proposed M Red Rocks Regional Landfill, Thoreau, NM RCRA MSW F Proposed M Rio Rancho Landfill, Rio Rancho, NM RCRA MSW F Approved M Sandoval County Landfill, Bernalillo, NM RCRA MSW F Proposed M Sandia National Laboratories, Albuquerque, NM RCRA NHWS Demo Complete M and CB San Juan County Landfill, Aztec, NM RCRA MSW F Approved M Valencia Landfill, Los Lunas, NM RCRA MSW F Approved M Oklahoma Alderson Landfill, McAlester, OK RCRA MSW F Installed M American Environmental, Sand Springs, OK RCRA MSW F Installed M Broken Arrow Landfill, Broken Arrow, OK RCRA MSW F Installed M Canadian Valley Landfill, Shawnee, OK RCRA MSW F Installed M Center Point Landfill, Prague, OK RCRA MSW F Approved M City of Sallisaw, Sallisaw, OK RCRA MSW F Approved M East Oak Landfill, Oklahoma City, OK RCRA MSW F Approved M Muskogee Community Landfill, Muskogee, OK RCRA MSW F Approved M Newcastle Landfill, Newcastle, OK RCRA MSW F Installed M Oklahoma Landfill, Oklahoma City, OK RCRA MSW F Installed M Osage Landfill, Bartlesville, OK RCRA MSW F Design M Porter Landfill, Porter, OK RCRA MSW F Installed M Quarry Landfill, Tulsa, OK RCRA MSW F Installed M Red Carpet, Meno, OK RCRA MSW F Approved M Southeast OKC Landfill, Oklahoma City, OK RCRA MSW F Installed M Southern Plains, Ninnekah, OK RCRA MSW F Approved M Stillwater Landfill, Stillwater, OK RCRA MSW F Approved M Texas Caliche Canyon Landfill, Lubbock, TX RCRA MSW F Proposed M City of Corsicana Landfill, Corsicana, TX RCRA MSW F Proposed/ Pending M
City of Fredericksburg Landfill, Fredericksburg, TX RCRA MSW F Proposed/ Pending M
City of Kerrville, Kerrville, TX RCRA MSW F Proposed/ Pending M
City of Lubbock Landfill, Lubbock, TX RCRA MSW F Installed M City of Snyder Landfill, Snyder, TX RCRA MSW F Proposed M City of Victoria Landfill, Victoria, TX RCRA MSW F Proposed/ Pending M
DFW Recycling Disposal Facility, Lewisville, TX RCRA MSW F Proposed/ Pending M

### 18 Site Program Type of Site Scale Status Type of Cover El Centro Landfill, Robstown, TX RCRA MSW F Proposed/ Pending M
Golden Triangle Landfill, Beaumont, TX RCRA MSW F Proposed/ Pending M
Itasca Landfill, Itasca, TX RCRA MSW F Proposed/ Pending M
Mexia Landfill Mexia, TX RCRA MSW F Proposed// Pending M
Pantex Plant (USDOE), Amarillo, TX RCRA CD F Installed M Pleasant Oaks Landfill, Mt. Pleasant, TX RCRA MSW F Proposed/ Pending M
Rio Grande Valley Landfill, Donna, TX RCRA MSW F Proposed/ Pending M
Sierra Blanca, Sierra Blanca, TX Texas Low Level Rad Rad Demo Complete CB
Turkey Creek Landfill, Alvarado, TX RCRA MSW F Proposed/ Pending M
Westside Landfill, Sledo, TX RCRA MSW F Installed M Region 7 Iowa Bluestem Landfill Site No. 1, Cedar Rapids, IA ACAP MSW Demo Complete M Bluestem Landfill Site No. 2, Cedar Rapids, IA ACAP MSW Demo Complete M Grundy County Landfill, Grundy Center, IA RCRA Cleanup MSW Demo Complete M

Kansas Barton County Landfill, Great Bend, KS RCRA MSW F Installed M Chanute Landfill, Chanute, KS RCRA MSW F Installed M Coffey County Landfill, Burlington, KS RCRA MSW F Installed M Holcomb Combustion Waste Landfill, Holcomb, KS RCRA IW Ash F Proposed M Johnson County Landfill, Shawnee, KS RCRA MSW F Installed M McPherson County Landfill, McPherson, KS RCRA MSW F Installed M Seward County Landfill, Liberal, KS RCRA MSW F Proposed M Missouri Electrical Power Plant, St. Louis, MO RCRA IW Ash Demo Complete M RCRA Solid Waste Unit at Former Wood Treating Plant, Kansas City, MO RCRA HWS F Installed M

Nebraska Douglas County Recycling and Disposal Facility, Bennington, NE ACAP MSW Demo Complete CB
Hastings Groundwater Contamination, Hastings, NE CERCLA MSW F Installed M Region 8 Colorado Buffalo Ridge Landfill, Keenesburg, CO RCRA MSW F Approved M Clear Springs Ranch Ash Monofill, Fountain, CO RCRA IW F Approved M Colorado Springs Landfill, Colorado Springs, CO RCRA MSW F Installed M

### 19 Site Program Type of Site Scale Status Type of Cover Conservation Services, Inc. Adams County, CO RCRA MSW F Installed M Custer County Landfill, Westcliffe, CO RCRA MSW F Installed M Denver Arapahoe Disposal Site, Arapahoe, CO RCRA MSW F Installed on closed cells M
Fort Carson, Colorado Springs, CO RCRA MSW F Installed M Kit Carson County Landfill, Burlington, CO RCRA MSW F Proposed M Mesa County Landfill, Grand Junction, CO RCRA MSW F Installed M Midway Landfill, Fountain, CO RCRA MSW F Installed M North Weld Landfill, Ault, CO RCRA MSW F Installed M Rocky Mountain Arsenal (US Army), Denver, CO DoD HWS Demo Complete M Rocky Mountain Arsenal (US Army), Denver, CO CERCLA HWS F Installed CB Southside Landfill, Pueblo, CO RCRA MSW F Approved M West Garfield County Landfill, Rifle, CO RCRA MSW F Installed M Montana Allied Waste of Montana, Missoula, MT RCRA MSW F Installed M City of Billings, Billings, MT RCRA MSW F Installed M City of Bozeman, Bozeman, MT RCRA MSW F Installed M City of Butte Landfill, Butte, MT RCRA MSW (old fill) F Installed M
City of Butte Landfill, Butte, MT RCRA MSW (new fill) F Approved M
Harve Class II Landfill, Havre, MT RCRA MSW F Proposed M High Plains, Great Falls, MT RCRA MSW F Installed M Lake County Landfill, Polson, MT ACAP MSW Demo Complete CB Lake County Landfill Full Scale, Polson, MT RCRA MSW F Approved CB Lewis & Clark County Landfill, Helena, MT ACAP MSW Demo Complete CB Mr. "M" Landfill, Lewiston, MT RCRA MSW F Installed M Sanitation, Inc., Lewistown, MT RCRA MSW F Installed M Unified Disposal District, Havre, MT RCRA MSW F Proposed M Valley County Landfill, Glasgow, MT RCRA MSW F Proposed M Valley View, East Helena, MT RCRA MSW F Installed M North Dakota Grand Forks Municipal Solid Waste Landfill, Grand Forks, ND RCRA MSW F Approved BE
Great River Energy - Coal Creek Station, Underwood, ND RCRA IW Ash Demo Installed M

South Dakota Mitchell Landfill, Mitchell, SD RCRA MSW F Approved M Municipal Sanitary Landfill (Sioux Falls Regional Municipal Landfill), Hartford, SD RCRA MSW F Approved M
Pierre Landfill, Pierre, SD RCRA MSW F Installed M Utah

### 20 Site Program Type of Site Scale Status Type of Cover Bayview Landfill, 6 miles N. of Elberta, UT RCRA MSW F Installed M Chester Class II Landfill, 5 miles north of Ephraim, UT RCRA MSW F Installed M Emery County Class I Landfill, Castle Dale, UT RCRA MSW F Installation ongoing M
Hill Air Force Base, Ogden, UT DoD Research Demo Complete CB Monticello Mill Tailings (USDOE), Monticello, UT CERCLA Rad Demo Complete CB Monticello Mill Tailings Repository, Monticello, UT CERCLA Rad F Installed CB Mountain View Landfill, Salt Lake City, UT RCRA CD Asbestos F Approved M
Sanpete Sanitary Landfill Cooperative White Hills Class I Landfill, Sanpete County, UT RCRA MSW F Approved M
Region 9 Arizona Blue Hills Regional Landfill, St. Johns, AZ RCRA MSW F Proposed M Butterfield Station Facility, Mobile, AZ RCRA MSW F Approved M Cactus Landfill, Florence, AZ RCRA MSW F Approved M Calmat Avondale Reclamation Landfill, Avondale, AZ RCRA CD F Approved M City of Eloy, Eloy, AZ RCRA MSW F Approved M City of Glendale Municipal Landfill, Glendale, AZ RCRA MSW F Approved M Cochise County Western Regional Landfill Facility, Huachuca, AZ RCRA MSW F Approved M
Copper Mountain Landfill, Wellton, AZ RCRA MSW F Approved M Gray Wolf Regional Landfill, Dewey, AZ RCRA MSW F Approved M Ironwood Non Municipal Landfill, Florence RCRA CD F Approved M Irvington Municipal Landfill, Tucson, AZ RCRA MSW/ CD F Installed M
La Paz County Regional Landfill, Parker, AZ RCRA MSW F Approved M Lone Cactus Landfill, Phoenix, AZ RCRA CD F Approved M Los Reales Landfill, Tucson, AZ RCRA MSW F Approved M Northwest Regional Landfill, Surprise, AZ RCRA MSW F Approved M Painted Desert Landfill, Joseph City, AZ RCRA MSW F Approved M Silver Bar Mine Regional Landfill, Florence, AZ RCRA MSW F Approved M Southwest Regional Solid Waste Landfill, Buckeye, AZ RCRA MSW F Approved M Speedway Construction Debris Landfill, Tucson, AZ RCRA CD F Approved M California Allied Imperial Landfill, Imperial, CA RCRA MSW F Installed M Altamont Landfill & Resource Recovery Facility, Livermore, CA ACAP MSW Demo Complete M
Altamont Landfill Closure, Livermore CA RCRA MSW F Conditional

ly Approved M
Anza Sanitary Landfill, Anza, CA RCRA MSW F Installed M Apple Valley Landfill, Apple Valley, CA ACAP MSW Demo Complete Varies Apple Valley Landfill, Apple Valley, CA RCRA MSW F Installed M Azusa Landfill, Azusa, CA RCRA MSW F Proposed M Bakersfield Sanitary Landfill, Bakersfield, CA RCRA MSW F Installed M

### 21 Site Program Type of Site Scale Status Type of Cover Benton Class III Landfill, Benton, CA RCRA MSW F Installed M Bishops Canyon Landfill, Los Angeles, CA RCRA MSW/ CD F Installed M
Bradley Landfill, Los Angeles, CA RCRA MSW F Installed M Burbank Landfill No. 3, Burbank, CA RCRA MSW F Design M Buttonwillow Landfill, Kern County RCRA MSW F Approved M California Valley Landfill, California Valley, CA RCRA MSW F Installed M Camp Pendleton Marine Corps Base, San Diego County, CA RCRA MSW/ CAMU F Installed M
Cedarville (East) Landfill, Cedarville, CA RCRA MSW F Installed M Chalfant Class III Landfill, Mono County, CA RCRA MSW F Installed M China Grade Sanitary Landfill, Bakersfield, CA RCRA MSW F Installed M Coachella Sanitary Landfill, Coachella, CA RCRA MSW F Installed M Eagleville Landfill, Modoc County, CA RCRA MSW F Installed M Edom Hill Sanitary Landfill, Riverside County, CA RCRA MSW F Installed M Edwards Air Force Base Operable Unit 7 Chemical Warfare Materiel, Lancaster, CA CERCLA HW/ MSW F Installed M
El Toro Marine Corps Air Station, El Toro, CA CERCLA HW/ MSW F Installed M
Forward Landfill, Manteca, CA RCRA MSW F Installed M Foxen Canyon Closed Class III Landfill, San Luis Obispo, CA RCRA MSW F Approved M
Frank R. Bowerman Landfill, Irvine, CA RCRA MSW F Approved M Gaffey Street Sanitary Landfill, Wilmington, CA RCRA MSW F Installed M Hesperia Landfill, Hesperia, CA RCRA MSW F Installed M Hirschdale Landfill, Hirschdale, CA RCRA MSW F Installed M Holtville Sanitary Landfill, Holtville, CA RCRA MSW F Proposed M Jolon Road Closed Class III Landfill, King City, CA RCRA MSW F Installed M Kettleman Hills Facility, Kettleman City, CA RCRA HW/ MSW F Proposed M
Kiefer Landfill, Sloughhouse, CA ACAP MSW Demo Complete M Kiefer Class III Municipal Landfill, Sloughhouse, CA RCRA MSW F Approved M Lake City Landfill, Lake City, CA RCRA MSW F Installed M Lamb Canyon Sanitary Landfill, Beaumont, CA RCRA MSW F Proposed M Lenwood-Hinkley Landfill, Lenwood, CA RCRA MSW F Installed M Lopez Canyon Sanitary Landfill, Los Angeles, CA RCRA MSW F Installed M Marine Corps Base Barstow, CA CERCLA HW/ MSW F Installed M
Mead Valley Sanitary Landfill, Perris, CA RCRA MSW F Installed M Midway Solid Waste Disposal Site, San Luis Obispo County, CA RCRA IW F Installed M
Milliken Landfill, Ontario, CA RCRA MSW Demo Complete M Milliken Landfill, Ontario, CA RCRA MSW F Installed M Monterey Peninsula Landfill, Marina, CA ACAP MSW Demo Complete M

### 22 Site Program Type of Site Scale Status Type of Cover Needles Sanitary Landfill, Needles, CA RCRA MSW F Installed M Newberry Springs Sanitary Landfill, Newberry Springs, CA RCRA MSW F Installed M
Norton Air Force Base (Landfill #2), San Bernardino, CA CERCLA MSW F Installed M
Ocotillo Class III Municipal Solid Waste Management Facility, Ocotillo, CA RCRA MSW F Installed M
Operating Industries Inc. Landfill, Monterey Park, CA RCRA HW/ MSW F Installed M
Phelan Landfill, Phelan, CA ACAP MSW Demo Complete M Phelan Landfill Full Scale, Phelan, CA RCRA MSW F Approved M San Marcos Landfill, San Marcos, CA RCRA MSW F Installed M Spadra Landfill, Pomona, CA RCRA MSW F Installed M Twentynine Palms Sanitary Landfill RCRA MSW F Installed M U.S. Marine Corps Air and Ground Combat Center (MCAGCC) at Twentynine Palms, Twentynine Palms, CA DoD MSW Demo Complete M
Yucaipa Landfill, Yucaipa, CA RCRA MSW F Installed M Hawaii Kaneohe Bay Marine Corps Base, Oahu, HI DoD MSW Demo Complete BE Nevada Nevada Test Site, NV (landfill U-3 ax/bl) DOE Research Rad Demo Complete M
New Austin Landfill, Austin, NV RCRA MSW F Proposed M U.S. Ecology Nevada Site, Beatty, NV RCRA HW F Approved M Region 10 Alaska Anchorage Pilot Study Site, Anchorage. AK RCRA MSW Demo Complete M City of Elim Landfill, Elim, AK RCRA MSW F Proposed M Elmendorf Air Force Base, Anchorage, AK RCRA MSW F Installed M Minchumina Landfill, Lake Minchumina, AK RCRA MSW F Proposed M Idaho Idaho National Engineering Laboratory, Idaho Falls, ID CERCLA HWS F Installed CB Oregon Finley Buttes Regional Landfill, Boardman, OR ACAP MSW Demo Complete M Washington Duvall Custodial Landfill RCRA MSW F Installed M Hanford 200-Area (USDOE), Richland, WA Prototype Barrier (BP-1) CERCLA Rad Demo Installed CB
Nonradioactive Dangerous Waste Solid Waste Landfill (DOE Hanford) CERCLA HWS F Proposed M

### 23 Definitions Approved A proposal to build an ET has been approved by the appropriate regulatory agency. Complete Associated with demonstrations and indicates the demonstration is complete. Proposed An ET design or proposal to construct an ET has been submitted to the appropriate regulatory agency Installed Construction complete. Legend ACAP Alternative Cover Assessment Program BE Bioengineered CAMU Corrective Action Management Unit CB Capillary Break CD Construction Debris Landfill CERCLA Comprehensive Environmental Response, Compensation, and Liability Act Demo Demonstration Project F Full Scale HW RCRA Subtitle C Hazardous Waste Facility HWS Hazardous Waste Site—Generally concerned with cleanup activities IW Industrial Waste Such as Coal Ash M Monolithic MSW Municipal Solid Waste Site MSW/CAMU MSW being used in a RCRA cleanup to consolidate potentially hazardous wastes NHWS Non-Hazardous Waste Site NRC Nuclear Regulatory Commission Rad Radioactive Waste RCRA Resource Conservation and Recovery Act

### 24 

# APPENDIX B DATA FROM TWO COMPARISO N

DEMONSTRATION PROJECTS

### 25 ALTERNATIVE LANDFILL COVER DEMONSTRATION (ALCD) DOE sponsored the ALCD, a large-scale field test of two conventional designs (RCRA Subtitle C and Sub

title D) and four alternative landfill covers (monolithic ET cover, capillary barrier ET cover, geosynthetic clay liner cover, and anisotropic [layered capillary barrier] ET cover). The test was conducted at Sandia National Laboratories, located on Kirtland Air Force Base in Albuquerque, New Mexico. Cover design information is available at http://www.sandia.gov/Subsurface/factshts/ert/alcd.pdf

. The ALCD collected information on construction, cost, and performance that is needed to compare alter

native cover designs with conventional covers. The RCRA covers were constructed in 1995, and the ET covers were constructed in 1996. All of the covers were 43 feet wide by 328 feet long and were seeded with native vegetation. The purpose of the project was to use the performance data to help demonstrate equiva

lency and refine numerical models to more accurately predict cover system performance (Dwyer 2003). The ALCD collected data on percolation using a pan lysimeter and soil moisture to monitor cover perfor

mance. Total precipitation (precip.) and percolation (perc.) volumes based on 5 years of data are provided below. The ET covers generally have less percolation than the Subtitle D cover for each year shown below. More information on the ALCD cover performance can be found in Dwyer 2003.

1997 (May 1-Dec 31) 1998 1999 2000 2001 2002 (Jan 1-Jun 25) Precip. (mm) Perc. (mm) Precip. (mm) Perc. (mm) Precip. (mm) Perc. (mm) Precip. (mm) Perc. (mm) Precip. (mm) Perc. (mm) Precip. (mm) Perc. (mm) Monolithic ET 267.00 0.08 291.98 0.22 225.23 0.01 299.92 0.00 254.01 0.00 144.32 0.00
Capillary Barrier ET 267.00 0.54 291.98 0.41 225.23 0.00 299.92 0.00 254.01 0.00 144.32 0.00
Anisotropic (layered capillary barrier) ET 267.00 0.05 291.98 0.07 225.23 0.14 299.92 0.00 254.01 0.00 144.32 0.00

Geosynthetic Clay Liner 267.00 0.51 291.98 0.19 225.23 2.15 299.92 0.00 254.01 0.02 144.32 0.00

Subtitle C 267.00 0.04 291.98 0.15 225.23 0.02 299.92 0.00 254.01 0.00 144.32 0.00 Subtitle D 267.00 3.56 291.98 2.48 225.23 1.56 299.92 0.00 254.01 0.00 144.32 0.74

### 26 ALTERNATIVE COVER ASSESSMENT PROGRAM (ACAP) EPA conducted the ACAP to evaluate the performance of alternative landfill covers. The ACAP began in 1998, and cover performance was evaluated at 13 sites. The sites were located in eight states from Califor

nia to Ohio and Georgia, and included a variety of landfill types, such as MSW, construction and demolition waste, and hazardous waste landfills. At eight sites, conventional and ET covers were tested side by side. At the remaining five sites, only ET covers were tested. The alternative covers typically were constructed with local soils and native vegetation. At two facilities, however, hybrid poplar trees were used as vegetation. Percolation performance was evaluated by pan lysim

eters. Soil moisture also was evaluated at all sites. Below are the field data for precipitation and percolation volumes at 11 of the sites. A summary of field cover performance for all 13 sites through 2004 is provided in Albright and Benson (2005). More information about ACAP is available on the Desert Research Institute website at http://www.dri.edu/acap-research

.

ACAP Water Balance Results
Site Location Cover Design Data Year (days) Precipitation (mm) Drainage
mm As % of Precipitation

Altamont CA ET 7/1/01 - 6/30/02 (365) 287 1.5 0.52% 7/1/02 - 6/30/03 (365) 425 2.5 0.59% 7/1/03 -6/30/04 (365) 291 64.5 22.16% Annual Average 22.8 7.76%

Membrane Composite 7/1/01 - 6/30/02 (365) 287 0.0 0.00% 7/1/02 - 6/30/03 (365) 425 4.0 0.94% 7/1/03 -6/30/04 (365) 291 0.2 0.07% Annual Average 1.4 0.34%

Apple Valley CA ET 7/1/02 - 6/30/03 (365) 86 0.4 0.47%
7/1/03 -6/30/04 (365) 106 0.0 0.00% Annual Average 0.2 0.24%

Membrane Composite 7/1/02 - 6/30/03 (365) 86 0.0 0.00% 7/1/03 -6/30/04 (365) 106 0.0 0.00% Annual Average 0.0 0.00% Compacted Clay 7/1/02 - 6/30/03 (365) 86 0.0 0.00% 7/1/03 -6/30/04 (365) 106 0.2 0.19% Annual Average 0.1 0.1%

Cedar Rapids IA ET 7/1/02 - 6/30/03 (365) 784 157.1 20.0% 7/1/03 -6/30/04 (365) 1742 365.7 20.99% Annual Average 261.4 20.5% Compacted Clay 7/1/02 - 6/30/03 (365) 784 94 11.98% 7/1/03 -6/30/04 (365) 1742 171 9.82% Annual Average 132.5 10.9%

Membrane Composite 7/1/02 - 6/30/03 (365) 784 22.0 2.81% 7/1/03 -6/30/04 (365) 1742 62.2 3.57% Annual Average 42.1 3.19%

### 27 ACAP Water Balance Results
Site Location Cover Design Data Year (days) Precipitation (mm) Drainage
mm As % of Precipitation

Omaha NB Thin ET with Capillary Break 7/1/01 - 6/30/02 (365) 560 3.45 0.62% 7/1/02 - 6/30/03 (365) 475 50.9 10.72% 7/1/03 -6/30/04 (365) 511 68.5 13.41% Annual Average 40.95 8.25%

Thick ET with Capillary Break 7/1/01 - 6/30/02 (365) 560 4.16 .74% 7/1/02 - 6/30/03 (365) 475 28.7 6.04% 7/1/03 -6/30/04 (365) 511 16.3 3.19% Annual Average 16.4 3.32%

Membrane Composite 7/1/01 - 6/30/02 (365) 560 1.03 0.18% 7/1/02 - 6/30/03 (365) 475 9.15 1.93% 7/1/03 -6/30/04 (365) 511 10.9 2.13% Annual Average 7.03 1.41%

Boardman OR ET Thin 7/1/01 - 6/30/02 (365) 164 0.0 0.00% 7/1/02 - 6/30/03 (365) 185 0.0 0.00% 7/1/03 -6/30/04 (365) 177 0.0 0.00% Annual Average 0.0 0.00%

ET Thick 7/1/01 - 6/30/02 (365) 164 0.0 0.00% 7/1/02 - 6/30/03 (365) 185 0.0 0.00% 7/1/03 -6/30/04 (365) 177 0.0 0.00% Annual Average 0.0 0.00%

Membrane Composite 7/1/01 - 6/30/02 (365) 164 0.0 0.00% 7/1/02 - 6/30/03 (365) 185 0.0 0.00% 7/1/03 -6/30/04 (365) 177 0.0 0.00% Annual Average 0.0 0.00%

Sacramento CA ET Thin 7/1/00 - 6/30/01 (365) 379 1.4 0.37% 7/1/01 - 6/30/02 (365) 456 96.2 21.10% 7/1/02 - 6/30/03 (365) 426 3.9 0.92% 7/1/03 -6/30/04 (365) 159 108.4 68.18% Annual Average 52.48 22.64%

ET Thick 7/1/00 - 6/30/01 (365) 379 0.0 0.00% 7/1/01 - 6/30/02 (365) 456 8.5 1.86% 7/1/02 - 6/30/03 (365) 426 0.0 0.00% 7/1/03 -6/30/04 (365) 159 0.6 0.38% Annual Average 2.28 0.56%

### 28 ACAP Water Balance Results
Site Location Cover Design Data Year (days) Precipitation (mm) Drainage
mm As % of Precipitation

Polson MT ET with Capillary Break 7/1/00 - 6/30/01 (365) 358 0.18 0.05% 7/1/01 - 6/30/02 (365) 308 0.39 0.13% 7/1/02 - 6/30/03 (365) 326 0.19 0.06% 7/1/03 -6/30/04 (365) 254 0.20 0.08% Annual Average 0.24 0.08%

Membrane Composite 7/1/00 - 6/30/01 (365) 358 1.16 0.32% 7/1/01 - 6/30/02 (365) 308 0.0 0.00% 7/1/02 - 6/30/03 (365) 326 0.0 0.00% 7/1/03 -6/30/04 (365) 254 0.5 0.20% Annual Average 0.42 0.13%

Helena MT ET with Capillary Break 7/1/00 - 6/30/01 (365) 252 0.0 0.00% 7/1/01 - 6/30/02 (365) 314 0.0 0.00% 7/1/02 - 6/30/03 (365) 288 0.0 0.00% 7/1/03 -6/30/04 (365) 103 0.0 0.00% Annual Average 0.0 0.00%

Albany GA ET (Trees) 7/1/00 - 6/30/01 (365) 1079* 134 12.42% 7/1/01 - 6/30/02 (365) 1039* 3.1 0.3% 7/1/02 - 6/30/03 (365) 1457* 218.2 14.98% Annual Average 118.4 9.23% Compacted Clay 7/1/00 - 6/30/01 (365) 909 291.9 32.11% 7/1/01 - 6/30/02 (365) 996 237.6 23.86% Annual Average 264.8 27.98%

Marina CA ET with Capillary Break 7/1/00 - 6/30/01 (365) 492 44.7 9.09% 7/1/01 - 6/30/02 (365) 401 64.2 16.01% 7/1/02 - 6/24/03 (359) 467 51.1 10.94% Annual Average 53.3 12.01% 7/1/00 - 6/30/01 (365) 492 9.0 1.82% 7/1/01 - 6/30/02 (365) 401 25.0 6.23% 7/1/02 - 6/24/03 (359) 467 36.0 7.71% Annual Average 23.3 5.25%

Monticello UT ET with Capillary Break 8/12/00 - 6/30/01 (323) 393 0.0 0.00% 7/1/01 - 6/30/02 (365) 213 0.0 0.00% 7/1/02 - 6/30/03 (365) 342 0.0 0.00% 7/1/03 -6/30/04 (365) 315 0.1 0.03% Annual Average 0.03 0.008% *Precipitation values at Albany include irrigation of the ET cover test section. Source: Albright and Benson 2005