6.3 Overpacking, Bulking & Waste Characterization

Overpacking, Bulking & Waste Characterization

Managing hazardous waste containers at an environmental cleanup or industrial remediation site requires moving, sampling, and packaging materials for transportation and treatment. When containers are structurally compromised or contain complex waste streams, field personnel must execute systematic overpacking protocols, representative waste sampling, hazard compatibility screening, and bulk consolidation.

Salvage Drums and Overpacking Procedures

When an original waste container (such as a standard 55-gallon steel drum) has suffered severe corrosion, puncture, mechanical damage, or structural failure, it cannot legally or safely be transported over public highways under Department of Transportation (DOT) regulations. The primary engineering solution is overpacking—placing the compromised container inside a larger, specially certified containment vessel known as a salvage drum (governed by 49 CFR 173.3(c)).

Material Selection and Specifications

Salvage drums are manufactured in various sizes and materials depending on the chemical characteristics of the waste:

• Steel Salvage Drums (85-Gallon or 110-Gallon): Fabricated from heavy-gauge carbon steel with epoxy or phenolic internal linings. Steel salvage drums provide high structural strength and are mandatory when overpacking containers holding flammable solvents, halogenated organics, or hydrocarbon mixtures that could degrade synthetic polymers.
• Polyethylene Salvage Drums (HDPE Overpacks): Made from high-density, UV-stabilized polyethylene. These overpacks provide superior chemical resistance against strong inorganic acids (such as sulfuric or nitric acid), strong caustics (sodium hydroxide), and oxidizing solutions that would rapidly corrode a steel salvage drum.
• Closure Mechanisms and Sealing: Salvage drums utilize heavy-duty bolt-ring closures with elastomeric gaskets (EPDM, Buna-N, or Viton) or threaded screw-top lids. Torque wrenches must be used to tighten bolt rings to the exact foot-pound specifications provided by the manufacturer to ensure an airtight, liquid-tight seal.

Step-by-Step Overpacking Protocol

1. Pre-Staging Inspection: Inspect the interior and exterior of the salvage drum for flaws, gasket deformation, or dirt that could compromise sealing.
2. Absorbent Bedding: Place a layer of inert absorbent material (such as vermiculite, clay absorbent, or sorbent pillows) in the bottom of the salvage drum. This cushions the inner drum and captures any residual leakage during transport.
3. Mechanical Ingestion: Using a forklift equipped with a hydraulic drum grapple, parrot-beak attachment, or overhead crane hoist, lift the damaged 55-gallon drum slowly and lower it vertically into the center of the salvage drum. Personnel must never position themselves directly beneath a suspended container.
4. Annular Void Filling: Pour additional dry absorbent material into the annular space between the inner drum and the salvage drum wall until the void is completely packed.
5. Closure and DOT Markings: Place the lid and gasket on the salvage drum, secure the bolt ring to manufacturer torque specifications, and apply mandatory DOT labeling. The container must be prominently marked with the words "SALVAGE DRUM" or "SALVAGE" in letters at least 12 mm (0.5 inches) high, along with the appropriate DOT hazard class diamond labels (e.g., Flammable Liquid, Corrosive) and UN packaging specification codes (e.g., UN 1A2T/Y300/S).

Drum Sampling Methodologies

Before waste can be bulked, treated, or shipped to a permitted Treatment, Storage, and Disposal Facility (TSDF), its precise chemical and physical properties must be characterized. Extracting samples from hazardous drums requires specialized tools and strict contamination controls.

Liquid Sampling Tools

• The Coliwasa (Composite Liquid Waste Sampler): The Coliwasa is the industry-standard instrument for collecting representative, depth-integrated liquid samples from drums. It consists of an outer glass, PTFE, or plastic tube with an internal stopper rod. As the open Coliwasa is lowered slowly to the bottom of the drum, liquid flows into the tube at the exact rate of descent. Once the bottom chime is reached, the operator pushes the stopper rod down into the bottom valve seat, sealing the column of liquid. When withdrawn, the Coliwasa retains a complete cross-sectional profile of all stratified layers (such as an upper layer of floating hydrocarbons and a lower layer of aqueous heavy metals).
• Drum Thief (Glass Pipette): A simple, heavy-walled borosilicate glass tube (typically 4 feet long and 1/2-inch inner diameter). The sampler lowers the tube into the liquid, places a gloved thumb tightly over the top opening to create a vacuum seal, and extracts the column. Drum thieves are inexpensive and disposable, eliminating cross-contamination, but are limited to low-viscosity liquids without solid particulates.
• Weighted Bottle Samplers and Peristaltic Pumps: Used for large storage tanks or drums containing viscous sludges where manual pipetting cannot draw fluid.

Solid and Sludge Sampling Tools

• Grain Sampler (Tri-level Trier): Consists of two concentric slotted metal or stainless steel tubes. The sampler inserts the closed tool into granular or powdered waste, rotates the inner tube to open the slots and collect material across the entire drum depth, and then rotates it closed before extraction.
• Open-Tube Soil Samplers & Augers: Used for hard, packed, or cohesive semi-solid hazardous sludges.

Field Compatibility Testing (HAZCAT Screening)

Laboratory analytical testing using gas chromatography/mass spectrometry (GC/MS) can take days or weeks. However, field crews need immediate data to safely segregate containers and prevent mixing incompatible chemical classes. Field personnel perform rapid Hazard Categorization (HAZCAT) testing on small sample aliquots (1 to 5 mL) inside a portable field fume hood or well-ventilated sampling tent.

Bulking Operations & Static Control

Bulking is the planned consolidation of identical or chemically compatible hazardous waste streams from dozens or hundreds of individual drums into high-capacity bulk transport vessels, such as 5,000-gallon vacuum tanker trailers, lined roll-off boxes, or Intermediate Bulk Containers (IBC totes). Bulking drastically reduces transportation freight costs, container handling labor, and TSDF tipping fees.

Mandatory Operational Controls During Bulking

1. Documented Compatibility Sign-Off: No drum may be transferred into a bulk container without verified, documented HAZCAT compatibility screening. Introducing a single drum of acid into an organic solvent tanker containing trace amines or cyanides can trigger a catastrophic exothermic runaway explosion or toxic gas release.
2. Closed-Loop Vapor Recovery: When transferring volatile organic compounds (VOCs) or toxic liquids into a tanker truck, the displaced vapor volume inside the tanker must not be vented into the open atmosphere. A closed-loop vapor recovery manifold must route off-gases through activated carbon adsorbers or scrubbers.
3. Static Electricity Grounding & Bonding: Pumping non-conductive flammable hydrocarbons through hoses and pipes generates high levels of electrostatic charge via fluid friction (streaming current). Before opening any bungs or initiating transfer pumps, operators must attach heavy-duty bonding cables between the source drum and receiving tanker, and connect the entire assembly to an earth ground rod (maintaining electrical resistance below 10 ohms to prevent static spark discharges).
4. Thermal Monitoring: Temperature probes must continuously monitor the liquid mass inside bulk receivers during consolidation to detect any unexpected exothermic temperature rises immediately.