• Three broad criteria relating to waste should be considered when determining the most appropriate type of sampling equipment to use for a given sampling strategy: physical parameters, chemical parameters, and waste-specific or site-specific factors.

Three broad criteria relating to waste should be considered when determining the most appropriate type of sampling equipment to use for a given sampling strategy:

• Physical parameters. Specific physical parameters affecting this selection include whether the wastes are free flowing or highly viscous liquids; crushed, powdered, or whole solids; contained in soil or groundwater; and homogeneous or heterogeneous, stratified, subject to separation with transport, or subject to other physical alterations due to environmental factors.
• Chemical parameters. The person collecting the sample should ensure that the sampling equipment is constructed of materials that are not only compatible with wastes, but are not susceptible to reactions that might alter or bias the physical or chemical characteristics of the waste.
• Waste-specific (e.g., oily sludges) or site-specific factors (e.g., accessibility issues). In addition to determining the type of sampling equipment used, the waste- and site-specific factors also may require modification of the chosen equipment so that it can be applied to the waste.

Once the physical, chemical, waste- and site-specific factors associated with the waste stream to be sampled have been identified and evaluated, appropriate sampling equipment can be selected. The equipment most typically used in sampling includes:

• Composite liquid waste samplers (coliwasas), weighted bottles, and dippers for liquid waste streams;
• Triers, thieves, and augers for sampling sludges and solid waste streams; and
• Bailers, suction pumps, and positive displacement pumps for sampling wells for groundwater evaluations.

Maintaining and decontaminating field equipment

Some analyses, such as pH, can be performed at the facility using field equipment. This equipment must be properly maintained, and where appropriate, calibrated to ensure data quality from the analyses. Maintenance of equipment can include routine cleaning, oil changes, or routine replacement of worn equipment components. The guidelines set forth in the operator’s manual of each piece of equipment should be followed since proper maintenance varies by model manufacturer. At a minimum, the equipment should be inspected, lubricated, and calibrated prior to any field work to ensure proper operation.