287 5 Subsurface Barrier Verification Prepared by* David J. Borns Sandia National Laboratories, Albuquerque, New Mexico Carol Eddy-Dilek Westinghouse Savannah River Company, Oxford, Ohio John D. Koutsandreas Florida State University, Tallahassee, Florida Lorne G. Everett L. Everett and Associates, LLC, Santa Barbara, California 5.1 OVERVIEW Waste containment system performance data are needed to conduct assessments that reveal the integrity of the barrier and verify that the operational aspects of the systems are functioning as designed. Biological, chemical, and physical phenomena in the subsurface or some combination thereof can impact the per- formance of subsurface barriers. To confirm the performance of the barrier and possibly determine where a failure has occurred, a well-planned and implemented monitoring system is required. The design service life of a containment system can range from as little as 10 years for slurry walls to more than 1000 years for radioactive waste storage structures. The longer the service life of a containment system, the greater the * With contributions by William R. Berti, DuPont Central Research and Development, Newark, Delaware; Skip Chamberlain, U.S. Department of Energy, Washington, DC; Thomas W. Fogwell, Fluor Hanford, Richland, Washington; John H. Heiser, Brookhaven National Laboratory, Upton, New York; John B. Jones, U.S. Department of Energy, North Las Vegas, Nevada; Eric R. Lindgren, Sandia National Laboratories, Albuquerque, New Mexico; William E. Lowry, Science and Engineering Associates, Inc., Santa Fe, New Mexico; Keri H. Moore, National Research Council, Washington, DC; Horace K. Moo-Young, Jr., Villanova University, Villanova, Pennsylvania; Michael G. Serrato, Westinghouse Savannah River Company, Aiken, South Carolina; Matthew C. Spansky, Westinghouse Savannah River Company, Aiken, South Carolina; 4040_C005.fm Page 287 Wednesday, September 21, 2005 12:28 PM © 2006 by Taylor & Francis Group, LLC 288 Barrier Systems for Environmental Contaminant Containment & Treatment probability of system failure. Because most components of containment systems exist underground, direct visual inspection is not tenable as a monitoring method. Thus, several traditional and evolving techniques of indirect and direct observa- tions need to be employed to obtain performance data. In terms of containment system effectiveness, two types of failure categories can be identified: structural failure and functional failure. Structural failure can occur without functional failure, although it can eventually lead to functional failure. Thus, verification monitoring of barrier structural and/or functional fail- ures is essential over the life of the barrier. Long-term monitoring is an important aspect in determining the integrity of the barrier over the lengthy lifetimes of many contaminants. This chapter discusses the state-of-the-art monitoring tech- nologies and recommends innovative methods such as in situ sensors to improve and reduce the cost of barrier monitoring. 5.2 GOALS Subsurface verification is integral to achieving acceptance of covers, permeable reactive barriers (PRBs), and subsurface barriers such as walls and floors. The roles of subsurface verification in this process of acceptance are as follows: • Meet or exceed regulatory requirements •Verify performance of engineered barriers •Verify conceptual models of contaminant fate and transport •Verify models for containment systems • Conduct long-term performance monitoring • Ensure identification of trigger levels for contingency actions At present, there are no specific regulations under the Comprehensive Envi- ronmental Response, Compensation, and Liability Act (CERCLA) or the Resource Conservation and Recovery Act (RCRA), and there is no regulatory guidance on subsurface barrier integrity or performance validation. The only regulatory standard for barriers is the RCRA requirement (40 CFR 264, Subpart N, Landfills) of a 10 –7 cm/s hydraulic conductivity at a thickness of 0.91 m. Additional standards may be added in the near term because the United States Environmental Protection Agency (USEPA) Office of Emergency and Remedial Response has launched the Superfund Initiative on Long Term Reliability of Containment (Betsill and Gruebel, 1995). The USEPA is scheduled to work with other U.S. agencies to develop technical guidance and methodologies to evaluate containment technologies. The American Society for Testing and Materials International (ASTM) has standards pertaining to barrier monitoring. Reference to these standards should be made when considering potential methods. The ASTM D18.21.02 committee, chaired by Lorne G. Everett, on vadose zone monitoring standards is responsible for publishing the list of vadose zone standards provided in Table 5.1. 4040_C005.fm Page 288 Wednesday, September 21, 2005 12:28 PM © 2006 by Taylor & Francis Group, LLC Subsurface Barrier Verification 289 5.3 VERIFICATION MONITORING Monitoring plays a key role at all stages in environmental management — from initial site discovery to site closure. Monitoring programs are essential in facili- tating site characterization and risk assessment, adequately conducting experi- mentation and evaluation, producing the data necessary for the performance evaluation, determining whether residual contamination exists that will prevent site closure, and verifying the effectiveness of containment structures. The focus of monitoring programs is necessarily site and time specific. For example, a soil remedial action may primarily require sampling during excavation and immedi- ately after remediation work is complete (site closure). For sediment and ground- water remedial actions, longer-term monitoring programs might be developed that have their roots in initial site characterization activities, continue through remediation, and extend for significant periods of time beyond termination of active remediation. In the case of groundwater, most sites begin with an inherited set of monitoring points already established and so part of the monitoring design process also includes determining to what extent the existing network can be used or must be abandoned or expanded. Depending on the selected remedial action (Table 5.2), monitoring programs can represent the majority of remedial action costs (e.g., monitored natural attenuation) or only a small percentage. Traditional characterization and verification monitoring programs tend to pre- specify sample numbers, locations, sampling frequency, and analytics (i.e., off- site laboratory analyses). This traditional type of data collection presents several TABLE 5.1 ASTM International Vadose Zone Monitoring Standards Vadose zone terminology (final) Soil pore-liquid monitoring (D 4696-92) Soil core monitoring (D 4700-91) Matrix potential determination (D 3404-91) Neutron moderation (D 5220-92/97) Soil gas monitoring (D 5314-93) Hydraulic conductivity (D 5126-90) Decontamination of field equipment (D 5088-90) Flux determination by time domain reflectometry (D 6565) Determining unsaturated and saturated hydraulic conductivity in porous media by steady- state centrifugation (D 6527) Horizontal applications of neutron moderation (D 6031) Frequency domain capacitance (Z4302Z) Field screening guidance standard (final) Water content determination (draft) Vadose zone borehole flow rate capacity test (draft) Air permeability determination (outline) Thermalcouple psychrometers (outline) 4040_C005.fm Page 289 Wednesday, September 21, 2005 12:28 PM © 2006 by Taylor & Francis Group, LLC 290 Barrier Systems for Environmental Contaminant Containment & Treatment TABLE 5.2 Progressive Monitoring Steps for a Remediation by Natural Attenuation Program Step Description Parties Involved I Establish point of compliance Specify point of compliance and the point at which monitoring must be conducted Regional administrator II Define what is to be monitored Demonstrate that natural attenuation is occurring according to expectations accomplished by including steps to: 1. Identify any potentially toxic transformation products; Determine if a plume is expanding (either downgradient, laterally or vertically) 2. Ensure no impact to down gradient receptors 3. Detect new releases of contaminants to the environment that could impact the effectiveness of the natural attenuation remedy 4. Demonstrate the efficacy of institutional controls that were put in place to protect potential receptors 5. Detect changes in environmental conditions (e.g., hydrogeologic, geochemical, micro- biological, or other changes) that may reduce the efficacy of any of the natural attenuation processes 6. Verify attainment of cleanup objectives Site operator and regional administra- tor (USEPA or the state-implementing agency) III Establish the time period for monitoring Continue as long as contamination remains above required cleanup levels, continue for a specified period (e.g., 1–3 years) after cleanup levels have been achieved to ensure that concentration levels are stable and remain below target levels. Regional administrator (USEPA or the state- implementing agency) IV Define how monitoring is to be done Demonstrate of the monitoring approach being appropriate and verifiables accomplished by including steps to: 1. Specify methods for statistical analysis of data, e.g., established tolerances, seasonal and spatial variability 2. Establish performance standards: • Information on the types of data useful for monitoring natural attenuation performance in the ORD publications (EPA/540/R-97/504, EPA/600/R-94/162) •EPA/600/R-94/123: a detailed document on collection and evaluation of performance monitoring data for pump-and-treat remediation systems Site operator and regional administrator (USEPA or the state- implementing agency) 4040_C005.fm Page 290 Wednesday, September 21, 2005 12:28 PM © 2006 by Taylor & Francis Group, LLC Subsurface Barrier Verification 291 limitations, particularly in the context of subsurface characterization and moni- toring. The costs are sometimes prohibitive, driven both by sample analytical costs and the capital investment required for monitoring wells. High monitoring costs, particularly for monitoring programs that extend over time, result in pres- sures to limit data collection. Limited data collection, in turn, results in decision- making that relies on data sets too sparse to adequately address the inherent heterogeneities and uncertainties associated with subsurface barrier systems. Finally, by prespecifying sample numbers and locations and relying on off-site TABLE 5.2 (continued) Progressive Monitoring Steps for a Remediation by Natural Attenuation Program Step Description Parties Involved • Standard test methods such as described in EPA SW-846, “Test Methods for Evaluating Solid Waste - Physical/Chemical Methods” or EPA publication, “Methods of Chemical Analysis for Water and Wastes” 3. Establish a time interval agreed upon by regional administrator or agency, including reporting maps, tabulation of data and statistical analysis, identification of trends, recommendations for changes in approach, evaluation of whether contaminants have behaved as predicted, and whether other remedies are required V Define action levels or process to be observed for monitoring Establish metrics for the monitoring system: 1. Establish background levels 2. Define what criteria shows that a plume is expanding or diminishing 3. Define what criteria shows that the conceptual model is applicable to a site 4. Determine the metrics of cleanup objectives and effectiveness Site operator and regional administrator (USEPA or the state- implementing agency) VI Define actions to be accomplished when action levels or processes are observed Establishment of action plan to follow attainment of metric: 1. Observe requirement to report to responsible party or agency statistically significant variance compared to background 2. Identify extent and nature of nonpredicted behavior (e.g., release) 3. Re-evaluate conceptual model and evaluate feasible corrective actions from previous and evolving contingency plan Site Operator will provide details of the monitoring program; should be provided to USEPA or the state-implementing agency as part of any proposed monitored natural attenuation remedy 4040_C005.fm Page 291 Wednesday, September 21, 2005 12:28 PM © 2006 by Taylor & Francis Group, LLC 292 Barrier Systems for Environmental Contaminant Containment & Treatment laboratory analyses with long turnaround times for analytical results, traditional characterization and monitoring programs are ill equipped to handle unexpected results. Fortunately over the last several years, technological advances have occurred in sensors, field analytics, and sample collection technologies that can help to lower costs and/or increase the effectiveness of monitoring programs (see Box 5.1). New approaches for designing and implementing environmental data collection programs have also been developed. A few of those innovative barrier- monitoring technologies are discussed in the subsections below. 5.3.1 M ETHODS Methods for barrier monitoring generally fall into broad classes such as measure- ment of moisture change, collection of moisture and gas samples, temperature, flow/velocity, barometric pressure, and settlement. An in-depth evaluation of barrier-monitoring science and technology is provided in the National Department of Energy Vadose Zone Science and Technology Roadmap [Idaho National Envi- ronmental Engineering Laboratory (INEEL), 2001]. 5.3.1.1 Moisture Change Monitoring Methods A number of methods are available for barrier-monitoring moisture change in soils (Everett et al., 1984; Wilson et al., 1995; Looney and Falta, 2000a,b). Many of these measurement techniques require laboratory testing to develop calibration curves relating instrument output to soil moisture content. Several of the more commonly used methods are described below. BOX 5.1 Rapid Field Characterization of Sediments Rapid field characterization techniques have been developed to speed assessment and reduce costs. These are field-transportable screening tools that provide measurements of chemical, biological, or physical parameters on a real-time or near real-time basis. Specific advantages include the ability to get rapid results to guide sampling locations, the potential for high data mapping density, and a reduced cost per sample. The approaches do have limitations including the nonspecific nature of some tests, sensitivity to sample matrix effects, and some loss in accuracy over conventional laboratory analyses. A variety of tools has been suggested for the rapid characterization of sediments, as shown in the table below. Screening-Level Analyses Recommended by the Assessment and Remediation of Contaminated Sediments Program for Freshwater Sediments Analytical Technique Parameter(s) X-ray fluorescence spectrometry (XRF) Metals UV fluorescence spectroscopy (UVF) Polycyclic aromatic hydrocarbons (PAHs) Immunoassays PCBs, pesticides, PAHs Microtox Acute toxicity 4040_C005.fm Page 292 Wednesday, September 21, 2005 12:28 PM © 2006 by Taylor & Francis Group, LLC Subsurface Barrier Verification 293 • Neutron probe — The neutron probe contains a source of neutrons and detectors to measure backscattered neutrons. The magnitude and energy of backscattering is primarily a function of the hydrogen content of the material surrounding the probe. To take readings, the neutron probe is lowered into the pipe and a continuous record of the response is obtained. Changes in the readings over time at a particular depth indicate changes in the number of hydrogen atoms, i.e., water content. The neutron probe must be calibrated for specific soils. This method • Time domain reflectometer — In this method, an electromagnetic end of the cable, a portion of the signal is reflected. The amplitude and travel time of the reflected portion depend on the dielectric properties of the soil, which in turn are strongly dependent on soil moisture content. The output is typically monitored on an oscilloscope or cable tester. These probes can be monitored remotely and have no direct analytical costs associated with them other than initial calibration. This tends to minimize life-cycle costs. • Thermocouple psychrometer — This instrument measures relative humidity within the soil pores, from which soil water potential and therefore moisture content can be calculated. Humidity is determined by the observed difference in temperatures between two thermocou- ples, one of which is exposed to the humidity in the surrounding soil and experiences cooling; the other thermocouple is located adjacent to the first but is isolated from the humidity. Moisture content is deter- mined from relative humidity on the basis of laboratory calibration. • Electromagnetic Induction (EMI) — EMI is a standard geophysical technique (Chapter 4) that is used to measure the conductivity of soil mass. At the ground surface, a transmitter coil generates an electro- magnetic field that induces eddy currents in the underlying subgrade. Secondary electromagnetic fields created by the eddy currents are measured by a receiver coil that produces an output voltage related to the subsurface conductivity. EMI is a rapid technique that is often used to delineate contaminant plumes, buried wastes, and other features that have conductivity contrasts with the surrounding soil. • Electrical resistivity tomography (ERT) — ERT is based on a large number of soil resistance measurements (Chapter 4) analyzed by math- ematical methods (e.g., finite difference models employing inversion techniques). Each resistance measurement involves several electrodes, some to apply a current through the soil and some to measure the voltage drop. The location and spacing of the electrodes determines the soil volume being measured; in general, larger electrode spacings are used at greater depth. Commonly, a linear series of electrodes is placed on the ground surface or beneath a landfill. An automatic monitoring 4040_C005.fm Page 293 Wednesday, September 21, 2005 12:28 PM © 2006 by Taylor & Francis Group, LLC wave is transmitted along a transmission cable buried in soil. At the is discussed in more detail in Section 5.9.1.1. 294 Barrier Systems for Environmental Contaminant Containment & Treatment system excites various pairs of electrodes according to a programmed sequence and measures the resistance between other pairs. When all desired combinations have been read, the resulting data are analyzed. The result is a two-dimensional contour map (i.e., a vertical or hori- zontal slice) of soil resistivity along the electrode line. Changes in moisture content over time appear as changes in resistivity. Laboratory calibration of subgrade soil is required to develop quantitative relation- ships. High-resolution resistivity has shown particular merit in both cap and subsurface liner monitoring but is not developed to a stage where it can be recommended in the near term. • Fiber-optic cable — These systems could be considered as one of the latest improvements in vadose zone sensor systems. Fiber-optic sys- tems already are measuring strain, temperature, acoustics, moisture, pH, flow, and chemicals. Fiber-optic cable could be included in the future applications of a monitoring system. The cable could be deployed in the perforated stainless-steel tubing laid down below the bottom liner during construction. Consideration could be given to including fiber-optic cable in the horizontal and vertical monitoring orientations. The cost advantages expected with the use of fiber-optic sensors are substantial. The risk of causing preferential flow paths associated with installing a very small diameter fiber cable is small relative to the other technologies. 5.3.1.2 Moisture Sampling Methods There are processes other than leakage through the barrier liner system that could cause changes in moisture content of the vadose zone. Examples include moisture release from the admix layer as it consolidates under the load of the waste, and vapor migration due to temperature changes caused by excavation, lateral mois- ture, or vapor movement into the trench (from outside the trench), and removal of subgrade soils. Moisture change resulting from such processes could be diffi- cult to distinguish from leachate. In addition, those methods described above in dissolved constituents as well as moisture content alone. In spite of these limi- tations, in the case of a RCRA cap, which is designed as an impermeable cap, elevated moisture migration rates alone can be used as an indicator of increased infiltration through the cap. To determine whether moisture is the result of leakage through the barrier liner, samples are collected and analyzed for constituents known to occur in the waste material. A number of techniques are available and are described in the literature (Everett, 1980; Everett et al., 1984; Wilson et al., 1995; Looney and Falta, 2000a,b). • Suction lysimeter — The suction lysimeter consists of a porous cup or plate attached to a small diameter tube leading to a sampling chamber. 4040_C005.fm Page 294 Wednesday, September 21, 2005 12:28 PM © 2006 by Taylor & Francis Group, LLC Section 5.3.1.1 that use electrical properties of the soil would be influenced by Subsurface Barrier Verification 295 The lysimeter is buried in the soil at the location where a sample is desired, and the tubing leads to an accessible location. To obtain a sample, a reduced pressure is applied to the lysimeter. Water in the soil matrix is sucked into the lysimeter and accumulates in the sampling chamber. There are various modifications utilizing additional tubes, check valves, and other components to allow samples to be retrieved from depth, but the basic operating principle is the same. • Absorbent pads — This method uses pads of absorbent material, such as felt, to collect soil moisture. One commercially available system (Flute) that has been used to collect samples beneath a radioactive waste landfill at Los Alamos National Laboratory (New Mexico), uses a cylindrical flexible membrane that holds the pads. The membrane is initially inside out, or inverted, and is everted as it is placed in the borehole so that the pads contact the borehole wall. After a period of time, when the pads have reached equilibrium with the surrounding material, the membrane is withdrawn, being inverted again during this process so that the pads are not contaminated. In soil materials, where an open borehole cannot be maintained over the long term, a permeable casing is required. • Sodium iodide gamma detector — This is a radiation-measuring instrument that is lowered down an access pipe. Rather than returning a sample to the ground surface, the detector measures the radioactivity of the surrounding soil. This method identifies contaminants that are gamma emitters in sufficient concentrations to be clearly detectable. • basin a few meters in dimension. It is lined with a geomembrane and backfilled with vadose zone soil. The floor of the basin slopes to a collection point, and a pipe leads from this point up to the ground surface. When a sample is required, a sampling pump is lowered down the pipe, where quantifiable measurements can be obtained. 5.3.1.3 Vadose Zone Monitoring Considerations To monitor flow and transport in covers, walls and floors, point-type probes such as tensiometers, time-domain reflectometry probes (TDR), suction lysimeters, and thermistors can be used as well as geophysical imaging methods such as seismic surveys, ground penetrating radar (GPR), and three-dimensional (3-D) ERT (Hubbard et al., 1997). Point-type probes may or may not intersect single flow paths (Figure 5.1). The shortcoming of point-type probe measurements is the difficulty of combining their responses in a meaningful way, such as integrat- ing or volume averaging responses from a number of point measurements. Geo- physical imaging methods complement point-type measurements by providing a spatially distributed view of subsurface conditions. Each measurement represents an average over space and time; however, the volume affected cannot be determined. 4040_C005.fm Page 295 Wednesday, September 21, 2005 12:28 PM © 2006 by Taylor & Francis Group, LLC Basin lysimeter — The basin lysimeter consists of a broad, shallow For additional details, refer to the discussion in Section 5.5.2.1. 296 Barrier Systems for Environmental Contaminant Containment & Treatment The shortcomings of geophysical methods are their lack of spatial resolution in detecting small barrier leaks, and the difficulty of correlating values such as electromagnetic responses and seismic velocities to hydrogeologic parameters governing fluid flow. Neither method can be used to observe flow in single fractures of fluid movement at the fracture matrix interface in sufficient detail to accurately represent transport through barriers. 5.4 VERIFICATION SYSTEM DESIGN One of the key issues discussed at the workshop was integrating the verification system design into the overall barrier design. The barrier must have a set of performance requirements that are site specific and risk based. Without a risk- based performance objective, the barrier is either intact and good or breached and unusable. As stated previously, none of the regulatory agencies has a set of criteria for a barrier. De facto , the regulators take a risk-based approach to approving such structures. Risk-based performance objectives are crucial to the successful deployment of subsurface barriers. This fact is demonstrated when comparing two identical failures in a barrier at distinctly different locations. Suppose an obstruction blocks the flow of grout during installation of a barrier wall, resulting in a 1 m 2 hole in the barrier wall. In one case the hole occurs within 1.2 m of the uppermost (shallowest) region of the barrier. In the other case, the hole is located at the bottom region of the barrier. Water flux through the waste site would result in contaminant mobilization FIGURE 5.1 Schematic of the performance of local-type and cross-borehole monitoring methods in a heterogeneous formation ( In Situ Remote Sensors and Networks, 1999e). 1. Tenslometers, ER probes, TDR provide local (6–20 om) measurements 2. Vacuum water sampling and neutron logging affect the 30–40 om near borehole 3. Cross-hole radar and 3D ER; tomography are effective within the zone of up to 10–12 m Preferred water 1 1 2 2 3 3 4040_C005.fm Page 296 Wednesday, September 21, 2005 12:28 PM © 2006 by Taylor & Francis Group, LLC [...]... on Nuclear and Hazardous Waste Management Pressure Transducer GPR plate Soil water status nest Settlement plate Cover perimeter C N Cabling Fiber optic 6 15 620 630 640 Cell 1 6 45 650 Southern extent of final cover system construction 6 05 610 6 15 620 6 25 630 6 35 640 6 45 650 655 660 6 65 670 670 6 65 660 655 650 6 45 640 6 35 630 6 25 620 610 FIGURE 5. 8 Layout of instrument nest on the final cover for Cell 1... 4040_C0 05. fm Page 302 Wednesday, September 21, 20 05 12:28 PM 302 Barrier Systems for Environmental Contaminant Containment & Treatment 5. 5.2.1 Long-Term, Post-Closure Radiation Monitoring Systems (LPRMS) An example of a new monitoring approach is the LPRMS that uses commercially available components in a reliable, low-cost, multipoint system for real-time, long-term, unattended monitoring of closed waste... monitoring and identification © 2006 by Taylor & Francis Group, LLC 4040_C0 05. fm Page 308 Wednesday, September 21, 20 05 12:28 PM 308 Barrier Systems for Environmental Contaminant Containment & Treatment of pollutants in the groundwater and subsoil below manufacturing facilities, including pharmaceutical, chemical, and food-processing facilities AEMS is expected to detect and identify leaks of contaminants... LLC 4040_C0 05. fm Page 312 Wednesday, September 21, 20 05 12:28 PM 312 Barrier Systems for Environmental Contaminant Containment & Treatment to the bottom of the trench Therefore, meaningful, post-closure, verification barrier- monitoring data should not be relied upon until a baseline has been established and moisture equilibration has stabilized Once stabilization has been achieved in the post-closure monitoring... has become the industry standard for soil moisture measurement, and its operation and data interpretation is well established The © 2006 by Taylor & Francis Group, LLC 4040_C0 05. fm Page 314 Wednesday, September 21, 20 05 12:28 PM 314 Barrier Systems for Environmental Contaminant Containment & Treatment principal advantages of this technique are repeatability, precision, and long-term viability Nothing... Page 316 Wednesday, September 21, 20 05 12:28 PM 316 Barrier Systems for Environmental Contaminant Containment & Treatment infiltration (geomembrane) and biointrusion (cobblestones) (Kumthekar et al., 2002) As of September 2003, Cell 1 was filled and capped with the monitoring system in place; Cell 2 was filled with capping planned for 2003; and Cells 3, 4, and 5 were partially filled The objective was to... LLC 4040_C0 05. fm Page 306 Wednesday, September 21, 20 05 12:28 PM 306 Barrier Systems for Environmental Contaminant Containment & Treatment SCAPS-Site characterization and penetration system Shaw The Shaw Group Inc 20-ton push truck VEHICLE • Push probe configurations -Sensors -Sampling • Grouting capability • Equipment decontamination • Hazardous environment protection DATA ACQUISITION AND ANALYSIS... drivers for change are cost and development of methods that enable the desired end states for remediation sites Only recently has the USDOE begun to design verification systems that meet or exceed the regulatory requirements for barriers Most communities still use old state-of-practice barrier verification systems This chapter discusses subsurface verification and monitoring for several types of barriers: landfill... many sites that are expected to have no on-site restoration personnel © 2006 by Taylor & Francis Group, LLC 4040_C0 05. fm Page 298 Wednesday, September 21, 20 05 12:28 PM 298 Barrier Systems for Environmental Contaminant Containment & Treatment 5. 5.1 SYSTEM APPROACH The technical process of total system performance assessment (i.e., integration design, prediction, and data collection) may appear complex... resources and was implemented because of its simplicity, low cost, and long-term viability The close-coupled monitoring system is monitored closely The frequency and duration of post-closure monitoring was established in consultation with the state and formally documented in the mixed waste landfill long-term care plan The cover and vadose zone monitoring system provides infiltration and performance information . performance in the ORD publications (EPA /54 0/R-97 /50 4, EPA/600/R-94/162) •EPA/600/R-94/123: a detailed document on collection and evaluation of performance monitoring data for pump -and- treat. 4040_C0 05. fm Page 301 Wednesday, September 21, 20 05 12:28 PM © 2006 by Taylor & Francis Group, LLC 302 Barrier Systems for Environmental Contaminant Containment & Treatment 5. 5.2.1. 306 Barrier Systems for Environmental Contaminant Containment & Treatment FIGURE 5. 6 SCAPS. SCAPS-Site characterization and penetration system Shaw e Shaw Group Inc. Pipe handling