priate place to accomplish considerable cost savings by commingling (i.e., mixing) waste materials. This is the process where compatible wastes from various sources are combined prior to disposal. Commingling is particularly suitable for waste solvents because disposal of liquid in a 55-gallon drum is generally much less expensive than disposal of the same volume of liquid in small containers. Because mixing waste requires transfer of waste between containers, it is imperative that the identity of all materials be known and their compatibility be understood. Safety in carrying out the procedures, including the use of personal protective devices as well as engineering controls such as fume hoods, must be of high priority.
In some cases, the disposal method and ultimate fate of the waste may require that different wastes not be accumulated together. For example, if commingled waste contains significant amounts of halogenated solvents (usually above 1%), disposing of the mixture can be markedly more costly. In such cases, segregation of halogenated and nonhalogenated solvents is economically favorable.
Based on federal regulations, storage at a central accumulation area is normally limited to 90 days, although more time is allowed for small-quantity generators or other special situations (180 or 270 days). The count begins when the waste is brought to the central accumulation area from the laboratory or satellite accumulation area. It is important to know that a special permit is required for long-term storage, that is, storage beyond the limit of 90 days (or 180 or 270 days, depending on the particular situation). Obtaining such a permit is usually too expensive and too time-consuming for most laboratory operations. (See RCRA and Chapter 9, section 9.D.4, for more information.)
Waste materials stored within a central accumulation area should be held in appropriate and clearly labeled containers, separated according to chemical compatibility as noted in the previous section. The label must include the accumulation start date and the words "Hazardous Waste." Fire suppression systems, ventilation, and dikes to avoid sewer contamination in case of a spill should be considered when such a facility is planned. Training of employees in correct handling of the materials as well as contingency planning for emergencies is expected to be a part of the central accumulation area operations.
Transportation of waste between laboratories (satellite accumulation areas) and the central accumulation area also requires specific attention to safety. Materials transported must be held within appropriate and clearly labeled containers. There must be provision for spill control in case of an accident during transportation and handling. For larger institutions, it is advisable to have some kind of internal tracking system to follow the movement of waste. If public roads are used during the transportation process, additional Department of Transportation (DOT) regulations may apply.
Final preparations for off-site disposal usually occur at the central accumulation area. Decisions on disposal options are best made here, as the larger quantities of waste are gathered. Identification of unknown materials not carried out within the laboratory must be completed at this point because unidentified waste cannot be shipped to a disposal site.
Laboratory waste typically leaves the generator's facility commingled in drums as compatible wastes or within a Lab Pack. Lab Packs are containers, often 55-gallon drums, in which small containers of waste are packed with an absorbent material. Lab Packs had been used as the principal method for disposing of laboratory waste within a landfill. However, recent landfill disposal restrictions severely limit landfill disposal of hazardous materials. Thus, the Lab Pack has become principally a shipping container. Typically, the Lab Pack is taken to a disposal facility, where it is either incinerated or unpacked and the contents redistributed for safe, efficient, and legal treatment and disposal.
Records are needed both to meet regulatory requirements and to help monitor the success of the hazardous waste management program. Because the central accumulation area is usually the last place where waste is dealt with before it leaves the facility, it is often the most suitable place for ensuring that all appropriate and required records have been generated.
For regulatory purposes, the facility needs to keep records for on-site activities that include
the quantities and identification of waste generated and shipped,
documentation of analyses of unknown materials if required,
manifests for waste shipping as well as verification of disposal, and
any other information required to ensure compliance and safety from long-term liability.
Records of costs, internal tracking, and so forth, can provide information on the success of the hazardous waste management program.
Hazard reduction is part of the broad theme of pollution prevention that is addressed in previous chapters