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Disposal of Activated Carbon from Chemical Agent Disposal Facilities Summary For the past two decades, the United States has been destroying its entire stockpile of chemical agents. At the facilities where these agents are being destroyed, effluent gas streams pass through large activated carbon filters before venting to ensure that any residual trace vapors of chemical agents and other pollutants do not escape into the atmosphere in exceedance of regulatory limits.1 All the carbon will have to be disposed of for final closure of these facilities to take place. In March 2008, the Chemical Materials Agency (CMA) asked the National Research Council (NRC) to convene a committee to study, evaluate, and recommend the best methods for proper and safe disposal of the used carbon from the operational disposal facilities. The statement of work reads as follows: STATEMENT OF TASK The National Research Council will establish an ad hoc committee to: examine the current heating, ventilation, and air conditioning (HVAC) systems of the U.S. Army's Chemical Materials Agency (CMA) that use activated carbon and consider the overall quantity and characteristics of the CMA HVAC secondary wastes assess the current plans and path forward for contaminated carbon management and disposition at Army chemical agent disposal facilities evaluate commercial and established industry alternatives for contaminated carbon disposal, i.e. best practices, processes and equipment suitable for use by the Army (considering both on-site and off-site usage), including characterization and pre-treatment requirements in the foregoing context, assess the scientific support needed for obtaining regulatory approvals at CMA facilities. In response to this request, the NRC Board on Army Science and Technology assembled the Committee to Examine the Disposal of Activated Carbon from the Heating, Ventilation, and Air Conditioning Systems at Chemical Agent Disposal Facilities. After discussion with the sponsor, the committee undertook to consider the disposition of all the carbon, exposed or unexposed to chemical agent, at the facilities. This report examines various approaches to handling carbon waste streams from the four operating chemical agent disposal facilities that use incineration technology developed by the Army. The approaches that will be used to dispose of carbon waste at each facility will ultimately be chosen bearing in mind local regulatory practices, facility design and operations, and the characteristics of agent inventories, along with other factors such as public involvement regarding facility operations. This report is intended to analyze and assess essential information on the various approaches for disposing of waste carbon from these facilities whether or not the carbon has been exposed to agent. This should enable readers to understand the technical reasoning underlying the committee’s findings and recommendations. Specific findings and recommendations are found in the individual chapters; the key findings and recommendations (General Findings 1-5 and General Recommendations 1-5) derived from the individual 1 Note that what are termed “carbon filters” in Army parlance are more accurately termed “carbon adsorption beds.”
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Disposal of Activated Carbon from Chemical Agent Disposal Facilities chapters are presented at the end of this Summary and in Chapter 7. Only three types of filter units are expected to ever be exposed to agents under normal operating conditions: (1) those that filter the heating, ventilation, and air conditioning (HVAC) air from the munitions demilitarization building (MDB), (2) the filters installed on the vent line from the agent collection system storage tanks, and (3) the canisters for the M-40 protective masks used by workers. The carbon from the initial banks of MDB HVAC air filters accounts for by far the largest share of exposed carbon. All of the other filter units installed to protect personnel or the environment will never have been exposed to agent unless some upset had occurred (e.g., release of agent to the atmosphere outside the MDB). The MDB, which is where the munitions or containers are opened and treated, has a cascading HVAC system that is designed to move ventilation air from clean, uncontaminated areas to areas having increasing levels of agent contamination. The HVAC system then discharges the air through banks of activated carbon filters. Each bank of the filter units, which are arranged in series, contains 48 metal trays each holding approximately 50 lb of carbon. An important feature of the system design is that operational procedures normally allow only the carbon in Banks 1 and 2 of the multibank adsorber units filtering the plant HVAC air to ever be exposed to agent. The carbon from Banks 3-6 of the HVAC filter units and the carbon from the pollution abatement system (PAS) filtration system (PFS) on each of the incinerators make up the bulk of the unexposed carbon. Estimates of the amounts of carbon that must be disposed of from the indicated sources at each site are tabulated in Tables S-1 and S-2. The ratio of unexposed to exposed carbon is approximately 4 to 1. TABLE S-1 Summary of Sources and Estimated Inventories (in Pounds) of Carbon Exposed to Agent at CMA Incineration Sites During Operations and Closurea Site ACS Laboratory MDB HVAC M-40 Mask Canistersb Other ANCDF 3,600 <100 153,800 1,400 UMCDF 4,800 <100 47,500 2,100 TOCDF 200 15,300c 159,000 3,100 20,800d PBCDF 1,200 <100 95,600 100 Total 9,800 15,300 455,900 6,600 20,800 aWeights may include carbon, carbon tray materials, and packaging. Information is as of September 29, 2008. Estimates of exposed carbon made on basis of anticipated on-site treatment. Quantities have been rounded. bCarbon from M-40 mask canisters, while normally not exposed to agent, is generally expected to be treated as exposed at most sites in view of the relatively small amounts involved. cThis carbon amount is the result of the significantly larger amounts and greater variety of materials tested over the longer duration of TOCDF operations compared to other sites. dThis carbon amount is the result of a ton container sampling operation unique to the site. SOURCE: Adapted from information provided to the committee by Timothy Garrett, Site Project Manager, ANCDF, as of September 29, 2008. The disposal of the exposed and unexposed carbon is regulated under the Resource Conservation and Recovery Act (RCRA) by the respective state regulatory agencies. Each facility has been issued a RCRA permit under the applicable state regulations. These permits establish waste characterization requirements, pertinent sampling/analysis methodologies, waste disposal methods, operating parameters, and closure requirements for each facility. The state-issued RCRA permits for all of the disposal facilities specify waste control limits (WCLs) or, for Oregon, permit compliance concentrations (PCCs) in parts per billion (ppb) of chemical agent below which a waste may be shipped off-site for disposal. The permits for the chemical agent disposal facilities at Anniston, Alabama, Pine Bluff, Arkansas, and Tooele, Utah (ANCDF, PBCDF, and TOCDF) set the WCL as 20 ppb for nerve agents GB and VX and 200 ppb for mustard agent, while the facility at Umatilla, Oregon (UMCDF) sets PCCs, which serve a similar purpose, at 13 ppb for VX, 16 ppb for GB, and 152 ppb for mustard.2 The primary analytical methodology for characterizing a waste at most of the chemical agent disposal facilities is set forth in EPA Publication SW-846; it includes the toxic chemical leaching procedure (TCLP), which is required to determine if a waste meets the toxicity characteristic definition.3 The existing requirements to transport activated carbon off-site for disposal are stated in each facility’s RCRA permit (Table S-3). Any changes require applying for a modification to the permit—the approval process takes approximately 1 year. Planned applica- 2 Brian O’Donnell, Chief, Secondary Waste, Closure Compliance, and Assessments, CMA, “Transportation risk assessment,” Presentation to the committee, July 24, 2008. 3 40 C.F.R. 261.24(a). A waste is considered hazardous for toxicity if the extract from the procedure contains a listed contaminant above a specified concentration, with mercury listed at 0.2 mg/L (Table 1).
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Disposal of Activated Carbon from Chemical Agent Disposal Facilities TABLE S-2 Summary of Sources and Estimated Inventories (in Pounds) of Unexposed Carbon Used at CMA Incineration Sites During Operations and Closurea Site PFS Carbon (Regular) Laboratory MDB HVAC PFS Sulfur-Impregnated Carbon Control Room Other ANCDF 115,500 15,400 414,700 69,300 15,400 12,400 UMCDF 270,000b 10,600 95,000 200,000b 5,300 17,300 TOCDF 0c 6,300 318,000 240,000d 5,000d 2,500d PBCDF 80,800e 15,900 127,500 48,500f 8,000 14,400 Total 466,300 48,200 955,200 557,800 33,700 46,600 aWeights may include carbon, carbon tray materials, and packaging. Information is as of September 29, 2008, unless otherwise noted. Estimates of unexposed carbon made on basis of anticipated off-site treatment. Quantities have been rounded. bInformation updated as of March 17, 2009. cPFS was only recently added at TOCDF for the processing of mercury-contaminated mustard agent and therefore only sulfur-impregnated carbon is to be used. dInformation updated as of March 19, 2009. eInformation updated as of March 18, 2009. Of this amount, 48,500 lb has already been shipped off-site. fInformation updated as of March 18, 2008. SOURCE: Adapted from information provided to the committee by Timothy Garrett, Site Project Manager, ANDCF, as of September 29, 2008. TABLE S-3 Current Status of Permit Requirements for Shipping Carbon Off-site from Chemical Agent Disposal Facilities Facility Requirement of the Existing Permit Planned Modification Application ANCDF Carbon exposed to <1 STL may be shipped off-site.a Carbon exposed to >1 STL must undergo extractive analysis prior to shipment. Carbon that tests <WCL may be shipped off-site. Filters from the agent collection system will be incinerated on-site. HVAC carbon >WCL after extractive analysis to be shipped off-site in accordance with bounding transportation risk assessment. Munitions demilitarization building HVAC Bank 1 carbon appears to be >WCL for GB. UMCDF Off-site shipment of agent-free carbon allowed if agent concentration is less than the PCC: 16 ppb for GB, 13 ppb for VX, and 152 ppb for mustard. The UMCDF plans to submit a Permit Modification Request to incorporate the agent extraction method for spent carbon into the Hazardous Waste Permit WAP following the programmatic validation of the method. TOCDF All carbon must be processed by carbon microminiaturization system and subsequently combusted in the deactivation furnace system.b Ship all carbon from the pollution abatement system filtration system and from the heating, ventilation, and air conditioning (HVAC) Banks 4-6 off-site. Considering using autoclave on remaining carbon until VSL <1 then shipping off-site. PBCDF The WAP requires on-site incineration of exposed carbon that is shown by extractive analysis to be greater than 20, 20, and 200 ppb for GB, VX, and H, respectively. The WAP allows off-site shipment to a TSDF for spent carbon that is shown by extractive analysis to be less than 20, 20, and 200 ppb for GB, VX, and H, respectively. Unexposed carbon can also be shipped, and generator knowledge is allowed in the determination of “unexposed.” None. NECDF Used agent-contaminated carbon is considered a listed hazardous waste (Waste Code 1001). However, extractive analysis was done to satisfy CMA bounding transportation risk assessment requirements. Agent-contaminated carbon has been shipped to a TSDF (a hazardous waste incinerator) for treatment. None. aThe one STL for GB and VX is 20 ppb; for HD, it is 200 ppb. bAlthough this is the existing requirement, the state and TOCDF have agreed that carbon will be stored until another treatment method is approved. SOURCE: Personal communications between Timothy Garrett, Site Project Manager, ANCDF, and Margaret Novack, NRC study director, February 24, 2009, February 25, 2009, and February 27, 2009.
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Disposal of Activated Carbon from Chemical Agent Disposal Facilities tions for permit modifications are also shown in the table. The regulations generally specify that the carbon will require extractive analysis to confirm that agent concentration(s) are below the respective WCLs or PCCs. Although all three chemical agents are strongly adsorbed on coconut shell activated carbon, they all react with the moisture that is also adsorbed on the carbon to form the expected hydrolysis products. In 2007, several carbon samples from Banks 1 and 2 of the MDB HVAC filter unit at ANCDF were analyzed for residual GB and VX at both government and contractor surety laboratories. These analyses verified that the agents GB and VX decompose by hydrolysis with the adsorbed water on the carbon. The amount of GB that must have been adsorbed on Bank 1 carbon during processing of GB munitions in the MDB is evidenced by the 13 wt percent of its hydrolysis product, isopropyl methylphosphonic acid (IMPA), which was found on the carbon by solid state magic angle spinning (MAS) nuclear magnetic resonance (NMR). In comparison, only a trace amount of the VX hydrolysis product, ethyl methylphosphonic acid (EMPA), was found on carbon from Bank 1. This small amount of the hydrolysis product is attributed to the low volatility of VX. Extractive analysis of HVAC filter unit carbon samples from NECDF by the system contractor laboratory indicated the presence of volatile VX impurities, hydrolysis by-products, and degradation products of the aminothiol group. At this time, no MDB HVAC carbon sample exposed to mustard agent HD from a chemical agent disposal facility is available for laboratory analysis. The shipping of agent-exposed carbon to off-site disposal facilities will require determination of the loading of agent on the carbon on a mass basis (mass of agent per mass of carbon). For parts-per-billion levels of detection of residual agents on carbon, solvent extraction of the adsorbed phase from the carbon sample followed by gas chromatography/mass spectrometry (GC/MS) analysis is being pursued. The Bank 1 carbon removed at ANCDF was analyzed by this method at Southwest Research Institute to determine the amounts of GB and VX remaining on the carbon. VX was below the WCL, but GB was above it. The GB result has been interpreted as a sign that GB re-forms from the hydrolysis products in the solvent during the extraction process. A way was found to limit this re-formation to ~6 ppb, but this modification to the standard method is not considered valid until other laboratories have reproduced the results. Early (unvalidated) measurements on the ANCDF Bank 1 carbon indicate that the residual GB (~129 ppb) is above the WCL limit (20 ppb), which means the carbon will not be transportable under the present permit. However, carbon containing GB at more than 20 ppb could be transported off-site if the transportation risk assessment (TRA) approved by state regulators and procedures was implemented to satisfy the bounding TRA values. These values are a function of accidental release scenarios assumed in the assessment and the frequency established for such release scenarios. In response to the third bullet in the statement of task for this study, the committee surveyed the common industrial practices for managing activated carbon. In commercial and industrial applications, activated carbon finds extensive use as an adsorbent for removal of a wide range of contaminants from liquids and gases. Demand for activated carbon in the United States was 363 million pounds in 2005, split approximately equally between granulated activated carbon and powdered activated carbon. The activated carbon used in chemical agent disposal facilities is granulated. Activated carbon is also used to adsorb a product such as a solvent from a process stream. In such applications, the adsorbed product is subsequently desorbed on-site for reuse. This last step, known as “carbon regeneration,” differs from “carbon reactivation,” which is a treatment process whereby adsorbed materials (adsorbates) on the carbon are destroyed and the structure of the activated carbon is restored for reuse. Reactivation is carried out in either a rotary kiln or multiple hearth furnaces where the carbon is heated in the presence of steam to 1800°F. There are essentially three treatment and disposal methods used for treating activated carbon from commercial operations: (1) reactivation, (2) landfill, and (3) incineration. If carbon from commercial industrial operations has been reactivated, vendors offer two options. One is to return the reactivated carbon to its former user. The other is to combine it with reactivated carbon from other sources and resell it. Reactivation is attractive to industrial users principally because it is less costly than disposal and purchase of freshly made activated carbon. When varying amounts of mercury were discovered in the mustard agent HD/HT ton containers at TOCDF, PBCDF, and UMCDF, CMA was required to develop a strategy to prevent emission of mercury during the incineration of HD/HT. Unlike agent, mercury persists in one form or another in the offgas leaving the PAS units of the incinerators. Testing results have shown
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Disposal of Activated Carbon from Chemical Agent Disposal Facilities that using sulfur-impregnated activated carbon in the PFS units during HD/HT processing is a good way to control mercury emissions. The HD/HT stockpiles contain bulk storage ton containers and munitions. All HD/HT ton containers have been found to contain some amount of mercury. Some HD/HT munitions may also contain mercury. The semisolid heels in the ton containers at TOCDF are the largest sources of mercury. Given the diverse uses of activated carbons at chemical agent disposal facilities and the focus of this report on disposal options for activated carbon from these facilities, it is important to explain that the adsorption of mercury onto activated carbon and the adsorption of agent onto activated carbon occur in physically different carbon filter units and at separate locations during HD/HT thermal destruction operations. There is virtually no opportunity for both mercury and agent to be adsorbed onto the same carbon bed during normal operations at chemical agent disposal facilities. Activated carbon is expected to be exposed to mercury exclusively in the PFS units, while it will be exposed to agent primarily in the initial HVAC filter systems. Although the ton containers will be opened to the atmosphere in the MDB rooms, mercury volatilization will be negligible because the vapor pressure of mercury in its elemental form is very low. Mercury salts would not have any vapor pressure. The closure plan for the Johnston Atoll Chemical Agent Disposal System (JACADS) required all used carbon to be incinerated on-site by micronization. The used carbon was first pulverized to a powdery consistency in a carbon micronization system and then blown into the deactivation furnace system, where it was incinerated. The committee has determined from the experience gained during the closure of JACADS that this process presents hazards, including the potential for serious dust explosions. At the closure of the Aberdeen Chemical Agent Disposal Facility (ABCDF), the used carbon filters (carbon contained in metal trays) were double bagged in polyethylene. The bags that had agent vapor screening levels (VSLs)4 of >1 were then placed in 95-gallon polyethylene drums, which were shipped by truck to the Veolia Environmental Services Facility in Port Arthur, Texas, where the used carbon and drums were incinerated without opening the drums. Bags containing carbon and agent at ≤1VSL were shipped to Veolia without drumming and incinerated as is. The NECDF permit had no requirement for sampling and analysis of the used carbon before shipment to an off-site treatment, storage, and disposal facility (TSDF). Under this permit NECDF managed the carbon that had been exposed to VX as a designated hazardous waste and shipped it off-site to Veolia for incineration. NECDF also shipped approximately 220,000 pounds of used unexposed carbon to Calgon Carbon Corporation for reactivation. This used unexposed carbon came from Banks 3 through 6 of the HVAC filter units. At ANCDF, PBCDF, and UMCDF, operating permits allow thermal treatment (1000°F for more than 15 minutes) of exposed carbon in the metal parts furnace. Presently, this practice is being used to treat the few carbon filter trays from the vent line of the agent collection system (ACS) storage tanks and carbon from the canisters of the M-40 protective masks. During this thermal treatment, the trays and canisters of carbon are held much longer than 15 minutes to ensure complete oxidation of the carbon and prevent it from smoldering when it is removed from the metal parts furnace. The TOCDF is planning to treat agent-exposed carbon in an autoclave to achieve decontamination sufficient for off-site shipment. This concept was being tested as this report was being written. CMA has proposed managing the carbon by on-site disposal of the small quantities of highly contaminated carbon from the ACS storage tank vent lines and the carbon from M-40 gas mask canisters. Off-site shipment has been proposed for all of the other carbon (exposed and unexposed) for disposal at a qualified TSDF, either by incineration or in a landfill. For all unexposed carbon, shipment will be based on generator knowledge that the carbon has never been exposed to agent. For exposed carbon, off-site disposal is based on using approved sampling methods to determine the amount of agent present in each polyethylene drum and comparing that amount to the amount allowed by a bounding TRA prepared and approved by CMA for use on all agent-contaminated secondary waste ship- 4 Vapor screening levels (VSLs) and short-term limits (STLs) are equivalent names (specified in RCRA operating permits) for the limits used in waste transport and disposal. They also supplement short-term exposure limits (STELs) for protecting workers’ health during plant operations as waste is generated and moved to storage areas within the plant. VSL and STL concentrations vary by agent and are the same values as STELs except that a VSL measurement is determined from air sampled for about 5 minutes instead of the 15 minutes of exposure applicable to STELs. A value of 1 VSL for GB, VX, and HD is equal to 0.0001 mg/m3, 0.00001 mg/m3, and 0.003 mg/m3, respectively.
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Disposal of Activated Carbon from Chemical Agent Disposal Facilities ments. Use of the bounding TRA at operating disposal facilities is expected to require acceptance by the state regulators for each site and for each state through which the materials are proposed to be moved. Use of the bounding TRA for exposed carbon will require special sampling and analysis since the adsorptive properties of activated carbon prevent the application of vapor screening to determine the amount of agent in the container. This methodology poses at least two challenges: The CMA must validate a sampling technique that ensures that agent-exposed carbon samples are representative of the total mass of carbon in the shipping container. The CMA must also show that the extractive analysis procedure to be used accurately measures the agent present on the exposed carbon at the ppb level. The committee believes that adding decontamination solution (NaOH) to the drums in which the exposed carbon would be shipped off-site is a potentially attractive method for ensuring the safety of off-site shipments. How much decontamination solution should be added must be determined as should how to ensure adequate wetting of carbon surfaces to achieve decontamination at levels safe for shipment. An additional option applicable to unexposed carbon (approximately 80 percent of the total carbon) may be disposal by transfer to a reactivation contractor. This provides a path for the reuse of unexposed carbon, thereby reducing the cost of its disposal. Such an arrangement should be contingent on termination of the Army’s ownership of and liability for the carbon as soon as it is transferred to the reactivation contractor. GENERAL FINDINGS AND RECOMMENDATIONS General Finding 1. About 80 percent of all the used activated carbon that has been or will be generated at the chemical agent disposal facilities operating under the Chemical Materials Agency has never been exposed to agent and can be treated as ordinary hazardous waste. This includes the carbon from Banks 3 to 6 of the heating, ventilation, and air conditioning filter units and the bulk carbon from the filter beds of the pollution abatement system filtration system. General Recommendation 1. All unexposed carbon (as determined by generator knowledge) should be disposed of off-site as a hazardous waste without further chemical analysis for agent or sent for reactivation if a contractor will accept it and assume ownership and liability. The choice of disposal method and treatment, storage, and disposal facility will be dictated by whatever other contaminants are present on the carbon. General Finding 2. Unless there is an unexpected upset resulting in contamination with agent, all of the sulfur-impregnated carbon that is to be used in the pollution abatement system filtration systems will not have been exposed to agent. Thus, based on generator knowledge the carbon can be sent off-site without further analysis for chemical agents. This carbon can be treated as a hazardous waste contaminated with mercury. General Recommendation 2. All of the sulfur-impregnated carbon used in the pollution abatement system filtration systems and not involved in an unexpected upset condition at a chemical agent disposal facility should be sent off-site. This carbon should be treated as a hazardous waste that is contaminated with mercury. General Finding 3. Treatment of all of the exposed carbon on-site in the metal parts furnace would seriously delay the closure of the currently operating Chemical Materials Agency chemical agent disposal facilities. General Recommendation 3. Only the carbon filter trays from the agent collection system tank vent lines and the canisters from the M-40 protective masks should be treated on-site in the metal parts furnace when the metal parts furnace is not performing its primary function of treating metal parts or other wastes. General Finding 4. Nerve agents GB and VX and mustard agent have been shown to degrade on activated carbon to their usual hydrolysis products by reacting with the moisture adsorbed on the carbon. This occurs both while the carbon is in use and after, during storage. Of the known analytical results, the concentrations of VX that remain on carbon samples from heating, ventilation, and air conditioning Bank 1 at the Anniston Chemical Agent Disposal Facility appear to be below the waste control limit (WCL) of 20 parts per billion. However, the remaining concentration of GB appears to be about 130 parts per billion, well above the WCL of 20 parts per billion. Thus, the carbon that has been exposed to GB cannot be sent off-site based on the waste control limits where those limits have been nego-
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Disposal of Activated Carbon from Chemical Agent Disposal Facilities tiated as permit compliance limits. The concentration of mustard that remains on the carbon filters had not been measured at the time this report was prepared. General Recommendation 4. Carbon that has been exposed to agent should be sent off-site under one of the following arrangements: Use of waste control limits (WCL) or permit compliance concentrations (PCC). If the agent concentrations on the exposed carbon are below the waste control limits or the permit compliance concentrations, the carbon can be shipped off-site for proper disposal at a waste treatment facility licensed to receive and treat this waste under existing regulations. For this arrangement it will be necessary to develop and validate analytical methods that accurately measure agent concentration for both GB and mustard. The methods must be capable of analyzing the agents on carbon that has been exposed to all three agents and that will have both the agents and their respective degradation products from hydrolysis adsorbed on the carbon. Use of a transportation risk assessment. By using the precedent negotiated at Aberdeen Chemical Agent Disposal Facility, if the mass of the agent on the carbon in a drum is less than specified by the Chemical Materials Agency transportation risk assessment (see Table 7-1) but >1 VSL, the drum can be transported to a treatment, storage, and disposal facility. Each chemical agent disposal facility will have to negotiate with the appropriate regulatory authorities to ensure proper permit conditions to ship exposed carbon off-site based on the transportation risk assessment and the validated analytical methods. Adding caustic solution to the drums. If the addition of caustic (NaOH) decontamination solution to a drum of exposed carbon wets the carbon, the caustic will hydrolyze the agents remaining on the exposed carbon to below the WCL or PCC. The drum containing the decontaminated carbon and decontamination solution can then be shipped off-site. The method of applying the decontamination solution must be negotiated and approved by the facility’s regulatory authority. Analysis for agent on the carbon should not be necessary with this arrangement. General Finding 5. Environmental Protection Agency Method 3571 appears to have provided an improved method detection limit for extractive analysis of VX on the Bank 1 carbon sample from the Anniston Chemical Agent Disposal Facility, but it must still be validated. Neither Environmental Protection Agency Method 3571 for HD nor modified Method 3571 for GB, which appears to minimize re-formation of GB during extraction and analysis, had been validated at the time this report was being prepared. General Recommendation 5. Both the original Environmental Protection Agency Method 3571 and the modified Method 3571 must be validated for use on carbon exposed to all three agents (GB, VX, and mustard) since the chemical agent disposal facilities expect to operate without changing out the heating, ventilation, and air conditioning filter units before closure.