Executive Summary
The U.S. Army is pilot testing chemical hydrolysis as a method for destroying the chemical agents stockpiled at Aberdeen, Maryland (HD mustard agent), and Newport, Indiana (VX nerve agent). The chemical agents at both locations, which are stored only in bulk ton containers, will be hydrolyzed (using aqueous sodium hydroxide for VX and water for HD) at slightly below the boiling temperature of the solution. The resulting hydrolysate at Aberdeen, which will contain thiodiglycol as the primary reaction product, will be treated by activated sludge biodegradation in sequencing batch reactors to oxidize organic constituents prior to discharge to an on-site federally owned wastewater treatment facility. The hydrolysate at Newport, which will contain a thiol amine and methyl phosphonic acid as the major reaction products, is not readily amenable to treatment by biodegradation. Therefore, organic constituents will be treated using supercritical water oxidation (SCWO).
In keeping with the statement of task for this study, the Committee on Review and Evaluation of the Army Chemical Stockpile Disposal Program (Stockpile Committee) gathered and reviewed information on the preliminary process design for the Aberdeen Chemical Agent Disposal Facility (ABCDF) and Newport Chemical Agent Disposal Facility (NECDF). The report focuses on the overarching issues in the process designs integrating individual processing steps, including potential alternative configurations and process safety and reliability.
The committee reviewed the acquisition design packages (ADPs) for the ABCDF and NECDF prepared by Stone and Webster Engineering Company for the U.S. Army. An ADP is a 60-percent design (approximately) that is used as a basis for competitive bids for completion of the design, construction, commissioning, and operation of each chemical agent disposal facility. The committee also reviewed additional test data and design modifications suggested by the selected systems contractors as they became available. The committee did not attempt to provide a detailed, comprehensive review of the process designs. Rather, this report evaluates major design changes, assesses the integration of processing steps, and identifies overarching issues that should be addressed to enhance the safety and efficacy of the processes. The committee also identifies additional development and testing that may be necessary.
A review of the proposed process designs for the ABCDF and NECDF indicated that the reliability of the integrated SCWO process step at the NECDF is the only significant obstacle in terms of design and development. Although the ability of SCWO to destroy organic constituents in the hydrolysate from VX has been demonstrated, the adequacy of the materials of construction for the SCWO reactor and downstream components and their reliability have not been adequately demonstrated. An engineering-scale test to demonstrate the fully integrated SCWO processing step and address these issues is scheduled for the spring of 2000.
The committee believes that the off-site treatment of hydrolysates may have significant cost and schedule benefits for the Chemical Stockpile Disposal Program and could be a contingency plan if difficulties arise during start-up and pilot testing of the on-site hydrolysate (postneutralization) process steps. Off-site treatment of the hydrolysates would require that suitable treatment and disposal facilities be identified and that public acceptance be obtained. Identification and public acceptance of off-site treatment and disposal facilities for hydrolysates may be challenging. However, at the Tooele Chemical Agent Disposal Facility (Tooele, Utah), aqueous waste streams that do not contain agent are currently being disposed of off site. The committee believes that the Army should maintain both on-site and off-site treatment and disposal options where possible. The development and verification of alternatives for the management of nonprocess wastes will also be important to avoid the on-site accumulation of these materials and delays during facility closure.
The committee also discusses: evaluations that should be completed; improvements in monitoring that would maximize worker safety; improvements in process efficiency through design changes; and more rapid process monitoring.
RECOMMENDATIONS
Recommendation 2-1. The alternative process for the removal, recovery, and disposal of volatile organic compounds (VOCs) recommended by Bechtel, the contractor for the Aberdeen Chemical Agent Disposal Facility (ABCDF), using air stripping followed by vapor-phase activated carbon absorption, is an improvement over the VOC removal process described in the acquisition design package and should be incorporated into the final design of the ABCDF. The activated carbon filter system should be designed to sustain high loading and enable rapid change-out of VOC-laden filter material.
Recommendation 2-2. The Army should continue to identify and pursue regulatory approval for waste management facilities to receive off-site shipments of brine from the supercritical water oxidation processing of VX hydrolysate at the Newport Chemical Agent Disposal Facility. However, given the modest cost of the equipment and the significant costs and processing delays that could result if shipping or receiving of the effluent were not allowed or became prohibitively expensive, the capability of processing the brine on site should be maintained.
Recommendation 2-3. The Army should conduct a comparative evaluation of the designs for enclosures to store and process chemical agent at the Aberdeen and Newport facilities to determine if similar enclosures could be used for storing and processing drained agent.
Recommendation 2-4. The Army should conduct a detailed analysis of the cascade ventilation system and its performance at both the Aberdeen and Newport facilities to determine the potential for agent migration during normal operations, maintenance, and upset conditions. A formal, structured evaluation should be performed that includes (1) the use of a dynamic model of the ventilation system to determine the migration of both lethal and sublethal agent concentrations and (2) reported instances of agent migration at the Tooele and Johnston Atoll baseline incineration facilities.
Recommendation 2-5. The design teams for the Aberdeen and Newport facilities, in coordination with the Army, should develop a formal means of sharing design information and developing best practices. Personnel at each facility should be designated and held accountable for facilitating the exchange of design information and lessons learned.
Recommendation 2-6. The end points for plant closure of the Aberdeen and Newport facilities should be identified (e.g., allowable residual contamination thresholds and possible future uses of the facilities). Plans for plant design, construction, and operation should include plans for facility closure, and reviews of plant designs should include preliminary plans for closure. Public involvement in determining this aspect of plant design should be encouraged.
Recommendation 3-1a. The Army should develop criteria and a schedule for resolving design and operational issues raised in the 1998 report, Using Supercritical Water Oxidation to Treat Hydrolysate from VX Neutralization, that have not yet been resolved for supercritical water oxidation operation at Newport. These issues include materials of construction, fabrication methods, system plugging, pressure let-down, and the duration of successful continuous pilot-scale operations.
Recommendation 3-1b. The Army should pursue the testing of materials of construction for treating VX hydrolysate by supercritical water oxidation (SCWO) more aggressively to finalize materials selection, design, and fabrication methods for critical components, including the SCWO reactor, inlet, and pressure let-down system. This testing should clearly define mechanisms and rates of corrosion and erosion under the range of anticipated process conditions. An independent panel of experts in materials of construction should evaluate testing to date and identify further needs to ensure that the reliability of the SCWO system is adequate to meet the processing objectives.
Recommendation 3-2. For worker protection and secondary containment, the final design package for the Newport facility must include the physical hazard controls (e.g., protective barricades) common to industrial operations involving high pressure and stored energy. Systems must be designed to minimize leaks, plugging, and ruptures of the supercritical water oxidation reactor and associated plumbing and protective barriers. Secondary containment equipment will also be necessary, including safety systems for handling high-purity oxygen at high pressure, such as protection against downstream fires and explosions caused by contact between combustible materials (e.g., activated carbon) and oxygen-enriched gas streams, under normal and upset conditions.
Recommendation 4-1. The Army should evaluate off-site management of hydrolysates both for potential cost and schedule benefits and as a contingency plan in case difficulties arise during start-up and pilot testing of the on-site (postneutralization) process steps.
Recommendation 4-2. The Army should define the quantity and characteristics of anticipated nonprocess waste streams and evaluate options for the final disposition of each type of waste. On-site processes should be developed and demonstrated for treating all agent-contaminated wastes. Methods of representative sampling and characterization of wastes should be developed to verify that treated wastes are free of agent to below appropriate risk thresholds.
Recommendation 5-1. Plant ventilation air at each facility should be monitored to verify the absence of agent in processing areas downstream of the toxic cubicles. Gaseous exhausts to the atmosphere should also be monitored to verify the absence of agent. Agent monitoring at each facility should incorporate the lessons learned from agent monitoring at the other disposal facilities.
Recommendation 5-2. After the transfer of each batch of hydrolysate from the reactors to storage tanks, the hydrolysate should be sampled from the hydrolysate storage tank and analyzed before subsequent processing to verify that it is free of detectable agent.
Recommendation 5-3. The criteria for releasing VX hydrolysate to subsequent processing steps at the Newport facility should be based on the 99.9999 percent agent destruction level required by the state of Indiana and an evaluation of worker and public risks associated with releases of agent in hydrolysate equal to or less than this destruction level (i.e., 330 ppb). Assessments of worker risk should include a thorough evaluation of risk mitigation measures and additional design and operating requirements necessary to satisfy this release criterion.
Recommendation 5-4. The Army should develop and demonstrate methods of chemical analysis to confirm the destruction of VX in the hydrolysate at the Newport facility. These methods should include procedural specifications and provisions for training so that confirmation at the required detection limits can be confirmed by testing by different analysts at multiple laboratories.
Recommendation 5-5. The Army should develop and demonstrate innovative analytical techniques that require significantly less time than present techniques to verify agent destruction for both VX and HD hydrolysates at the required detection limits.
Recommendation 6-1. Quantitative risk assessments and hazard evaluations for both the Newport and Aberdeen facilities should be carried out as early as possible during facility design, and the findings from these assessments should be used in both the design and future operation of the facilities to minimize risk and maximize safety.
Recommendation 6-2. Schedule risk should be evaluated for the Aberdeen and Newport facilities in the context of program implications and public risks and appropriate contingency plans developed if needed.
