7.2 Mixing, Loading & Container Decontamination

Mixing, Loading & Container Decontamination

Among all operational tasks performed by certified applicators, mixing and loading pesticides presents the greatest statistical hazard of acute chemical poisoning, severe ocular injury, and catastrophic point-source environmental contamination. While field application involves diluted spray solutions (typically 95% to 99% water), mixing and loading requires direct handling of 100% undiluted chemical concentrates. Pouring, measuring, and transferring concentrated liquids, wettable powders, and emulsifiable formulations generate splashes, toxic vapors, and airborne dusts that dramatically elevate dermal and inhalation exposure risks.

Executing safe mixing and loading operations requires a multi-layered defense combining specialized handler PPE, engineered containment pads, backflow prevention devices, and rigorous container decontamination protocols.

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1. Mixing & Loading Hazard Profile & Mandatory Handler PPE

+-----------------------------------------------------------------------------+
|                   MIXING & LOADING PPE & HAZARD DEFENSE                     |
|                                                                             |
|   [PRIMARY EXPOSURE RISKS]             [MANDATORY HANDLER PPE]              |
|   - Splashing undiluted liquid into    - Heavy Chemical-Resistant Apron     |
|     eyes, face, or chest                 (covers chest to mid-calf)         |
|   - Inhaling concentrated dusts from   - Chemical Splash Goggles & Shield   |
|     dry wettable powders / granules    - Nitrile / Neoprene Gloves (Cat A-H)|
|   - Catastrophic hose rupture or       - Chemical-Resistant Rubber Boots    |
|     tank overfill at loading pad       - NIOSH Respirator (OV/P100 if label)|
+-----------------------------------------------------------------------------+

Handler Personal Protective Equipment

Because of the extreme exposure potential when handling undiluted active ingredients, pesticide product labels mandate specialized mixing/loading PPE that exceeds standard application requirements:

1. Chemical-Resistant Apron: A heavy-duty, liquid-proof apron constructed of nitrile, butyl rubber, neoprene, or barrier laminate that covers the handler's body from the upper chest down to the mid-calf, shielding against accidental concentrate splashes when pouring.
2. Chemical Splash Goggles & Face Shield: Standard safety glasses with side shields are inadequate for mixing and loading. Handlers must wear tight-fitting, non-vented or indirectly-vented chemical splash goggles paired with a full-face shield to protect eyes and facial skin from pressurized chemical splashes.
3. Chemical-Resistant Gloves: Heavy-gauge, unlined nitrile, neoprene, or barrier laminate gloves (EPA Chemical Resistance Categories A through H) with gauntlets extending up the forearm. Leather, cotton, canvas, and flock-lined gloves are strictly prohibited because they absorb concentrates and trap chemicals against the skin.
4. Chemical-Resistant Footwear: Seamless rubber or neoprene work boots worn with pant legs pulled down over the outside of the boots to prevent funneling spilled liquid into the footwear.
5. Respiratory Protection: A NIOSH-approved half-mask or full-mask air-purifying respirator equipped with organic vapor (OV) cartridges and P100 particulate pre-filters when handling volatile concentrates or pouring dusty dry powders.

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2. Impermeable Mixing/Loading Containment Pad Architecture

Mixing and loading on bare soil or gravel creates severe point-source contamination. Over years of operation, minor repetitive drips, leaks, and tank washdowns saturate the underlying soil profile, creating concentrated plumes of active ingredient that leach directly into subterranean drinking water aquifers. Commercial facilities, large agricultural operations, and golf course maintenance hubs should utilize a dedicated mixing and loading containment pad.

+-----------------------------------------------------------------------------+
|                  MIXING & LOADING CONTAINMENT PAD SYSTEM                    |
|                                                                             |
|   +---------------------------------------------------------------------+   |
|   | REINFORCED CONCRETE PAD (Sealed with Chemical-Resistant Epoxy)      |   |
|   | - Sloped Floor (1% to 2% grade toward center collection sump)       |   |
|   | - Perimeter Curbing (Holds 110% to 125% of largest single tank)     |   |
|   |                                                                     |   |
|   |                  [CENTER COLLECTION SUMP]                           |   |
|   |                             |                                       |   |
|   |                             v (Dedicated Diaphragm Pump)            |   |
|   |                [RINSATE HOLDING TANKS: Labeled]                     |   |
|   |                - Herbicide Rinsate Tank                             |   |
|   |                - Insecticide/Fungicide Rinsate Tank                 |   |
|   +---------------------------------------------------------------------+   |
|                                                                             |
|   <====== REUSED AS CARRIER DILUENT IN NEXT COMPATIBLE TANK BATCH ======>   |
+-----------------------------------------------------------------------------+

Pad Engineering Standards:

• Paved Concrete Surface: Constructed of high-density, crack-resistant reinforced concrete sealed with a chemical-proof coating (polyurethane, epoxy, or polyurea).
• Containment Curbing & Capacity: Perimeter concrete curbs must be engineered to retain at least 110% to 125% of the total capacity of the largest single spray tank that will be loaded on the pad, preventing spilled concentrate or washdown water from escaping onto adjacent soil.
• Sloped Floor & Sump Collection: The pad floor must slope at a 1% to 2% grade toward a shallow, liquid-tight collection sump equipped with a dedicated chemical transfer pump.
• Rinsate Management & Recycling: Collected pad washings and tank rinsate are pumped into dedicated, clearly labeled storage tanks (segregated by chemical class, e.g., "Corn Herbicide Rinsate"). This collected rinsate is subsequently recycled by using it as carrier diluent water in future compatible spray batches, provided the total chemical concentration does not exceed maximum label rates.

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3. Water Supply Protection & Backflow Prevention

One of the most dangerous environmental accidents during sprayer filling is back-siphoning (backflow). If the water supply pump fails, municipal water main pressure drops, or another valve on the farm opens while a water supply hose is submerged inside a pesticide spray tank, a powerful hydraulic vacuum (siphon) is created. This vacuum draws hundreds of gallons of toxic chemical solution backward through the fill hose directly into the private drinking well or municipal water distribution grid.

+-----------------------------------------------------------------------------+
|                        AIR GAP BACKFLOW PREVENTION                          |
|                                                                             |
|         [WATER SUPPLY PIPE / HOSE] (Inside Diameter = D)                    |
|                     |                                                       |
|                     |  <--- AIR GAP >= 2 x D (Minimum 1.0 inch)             |
|                     |       (Unobstructed physical vertical air space)      |
|                     v                                                       |
|         ======================= (Top Rim / Flood Level of Spray Tank)       |
|         |                     |                                             |
|         |  PESTICIDE MIXTURE  | * FILL HOSE MUST NEVER BE SUBMERGED *       |
|         |                     |                                             |
+-----------------------------------------------------------------------------+

1. The Physical Air Gap (Gold Standard)

• The Air Gap Standard: The simplest, most foolproof backflow prevention method. An unobstructed, physical vertical air space must be maintained between the lowest point of the water supply pipe/hose discharge and the flood-level rim of the spray tank.
• Dimension Calculation: The vertical air gap distance must be at least twice the internal diameter of the water supply pipe ($2 \times D$), and never less than 1.0 inch. $\text{Minimum Air Gap} = 2 \times \text{Inside Diameter of Supply Line}$ Example: If filling with a 2-inch inside diameter water supply hose, the vertical separation between the hose end and the spray tank rim must be a minimum of 4 inches ($2 \times 2\text{ in} = 4\text{ in}$). If using a 3-inch hose, the minimum air gap is 6 inches.
• Submersion Prohibition: The water supply hose must NEVER be submerged below the surface of the spray liquid or inserted deep into the tank neck.

2. Mechanical Backflow Preventers

If a physical air gap cannot be visually maintained (such as in closed-loop automated filling systems), applicators must install an approved mechanical backflow prevention device on the water supply line:

• Reduced Pressure Zone (RPZ) Valve: An assembly consisting of two independently acting check valves separated by a hydraulically operating relief chamber. If supply pressure drops, the relief valve vents to the atmosphere, preventing any backward fluid movement. RPZ devices are mandatory for commercial connections to public water mains.
• Double Check Valve Assembly (DCVA): Suitable for low-hazard cross-connections, consisting of two spring-loaded check valves in series.

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4. Container Decontamination: Immediate Rinsing Protocol

Empty, unrinsed pesticide containers represent a severe toxic hazard. A typical "empty" 2.5-gallon plastic jug retains between 1 to 3 ounces of concentrated active ingredient adhering to the interior sidewalls, handle, and cap threads. If left uncleaned, this residue dries into an insoluble, hardened chemical cake that resists removal, permanently contaminating the plastic and converting the jug into regulated hazardous waste.

[!IMPORTANT] The Immediate Rinsing Imperative: Pesticide containers must be decontaminated IMMEDIATELY upon emptying while the chemical residues remain wet. Once dried, residues cannot be fully extracted, preventing the container from entering agricultural recycling programs. All rinsate generated during cleaning must be poured directly into the spray tank as part of the primary mix water.

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5. Triple-Rinsing vs. Pressure Rinsing Protocols

Applicators have two EPA-approved mechanical methods for container decontamination: Triple-Rinsing and Pressure Rinsing. Both protocols achieve $>99.999%$ residue removal when executed correctly.

+-----------------------------------------------------------------------------+
|                      THE 5-STEP TRIPLE-RINSING PROTOCOL                     |
|                                                                             |
|   [STEP 1: INITIAL DRAIN]       ---> Drain container into spray tank for    |
|                                      30 seconds until drips stop.           |
|                                                                             |
|   [STEP 2: ADD CLEAN WATER]     ---> Fill container 1/4 to 1/3 full with    |
|                                      clean water.                           |
|                                                                             |
|   [STEP 3: CAP & SHAKE]         ---> Replace cap tightly; shake, rotate, and|
|                                      invert vigorously for 30 seconds.      |
|                                                                             |
|   [STEP 4: DRAIN RINSATE]       ---> Pour rinsate into spray tank, draining |
|                                      for 30 seconds until drips stop.       |
|                                                                             |
|   [STEP 5: REPEAT TWICE]        ---> Repeat Steps 2 through 4 TWO MORE      |
|                                      times (Total of 3 complete rinses).    |
+-----------------------------------------------------------------------------+

The 5-Step Triple-Rinsing Protocol (Manual Method)

1. Step 1 (Drain): Empty the concentrated pesticide into the spray tank. Hold the container vertically upside down over the tank fill opening for at least 30 seconds until liquid flow reduces to occasional, slow drips.
2. Step 2 (Add Water): Add clean water to the container until it is approximately 1/4 to 1/3 full (e.g., add 2 to 3 quarts of water to a 2.5-gallon jug).
3. Step 3 (Shake & Invert): Securely replace the cap. Shake, swirl, and invert the container vigorously for at least 30 seconds so the wash water thoroughly rinses all internal surfaces, the bottom corners, the hollow handle, and the cap threads.
4. Step 4 (Drain Rinsate): Remove the cap and pour the rinsate directly into the spray tank opening, holding the container to drain for 30 seconds until drips cease.
5. Step 5 (Repeat): Repeat Steps 2 through 4 two additional times for a total of three full rinses. The resulting rinsate becomes part of the total carrier volume in the active spray mixture.

Pressure Rinsing Protocol (Mechanical High-Pressure Probe)

Pressure rinsing utilizes a specialized, pointed metal probe equipped with a multi-directional rotating high-pressure spray nozzle connected to a pressurized clean water supply ($40\text{ to }60\text{ PSI}$).

+-----------------------------------------------------------------------------+
|                          PRESSURE RINSING MECHANICS                         |
|                                                                             |
|   [EMPTY JUG DRAINED 30 SEC]  ---> Inverted over spray tank opening         |
|                                                                             |
|   [PUNCTURE WITH PROBE]       ---> Pointed probe punctures lower sidewall   |
|                                    or bottom of container                   |
|                                                                             |
|   [ACTIVATE 40-60 PSI SPRAY]  ---> Rotate probe 360° for 30 to 60 SECONDS   |
|                                                                             |
|   [CONTINUOUS GRAVITY DRAIN]  ---> All wash rinsate drains directly into    |
|                                    spray tank concurrently                  |
+-----------------------------------------------------------------------------+

• Procedure: Empty the container into the spray tank for 30 seconds. Invert the jug over the tank opening. Push the sharp pointed probe through the lower sidewall or bottom of the plastic container. Turn on water pressure ($40\text{–}60\text{ PSI}$) and rotate the probe continuously for 30 to 60 seconds, allowing all rinsate to drain directly into the spray tank.
• Key Advantages: Pressure rinsing is significantly faster than triple-rinsing, provides superior mechanical scouring of caked corners, and automatically punctures the container in a single step.

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6. Container Puncturing, ACRC Recycling & Missouri Open Burning Ban

Once a container has been triple-rinsed or pressure-rinsed, it is legally classified as non-hazardous solid waste under RCRA and Missouri law, requiring proper disposal or recycling.

+-----------------------------------------------------------------------------+
|                 POST-RINSING CONTAINER DISPOSAL HIERARCHY                   |
|                                                                             |
|   [1. PUNCTURE SIDEWALL / BOTTOM]   ---> Renders container unusable;        |
|                                          prevents accidental reuse.         |
|                                                                             |
|   [2. REMOVE CAPS & LABEL FOILS]    ---> Caps/booklets are non-recyclable;  |
|                                          discard in sanitary trash.         |
|                                                                             |
|   [3. ACRC PLASTIC RECYCLING]       ---> Preferred stream: chipped into     |
|                                          industrial plastic pellets.        |
|                                                                             |
|   [4. LICENSED SANITARY LANDFILL]   ---> Secondary stream if recycling      |
|                                          is unavailable in county.          |
|                                                                             |
|   [STRICT BAN: OPEN BURNING]        ---> ILLEGAL in Missouri; generates     |
|                                          toxic dioxins & heavy fumes.       |
+-----------------------------------------------------------------------------+

1. Mandatory Container Puncturing

Immediately following rinsing, the applicator must puncture the bottom and sidewalls of plastic jugs using a utility knife, shears, or the pressure rinse probe, and crush or slit bags.

• Critical Purpose: Puncturing renders the container permanently unusable and prevents disastrous reuse on farms or homes as drinking water jugs, gasoline cans, or animal feed buckets.

2. Recycling via the Ag Container Recycling Council (ACRC)

• The Ag Container Recycling Council (ACRC) and the Missouri Department of Agriculture sponsor statewide plastic container recycling programs.
• Clean, triple-rinsed or pressure-rinsed high-density polyethylene (HDPE #2) jugs (with caps, label booklets, and foil induction seals removed) are collected at regional dealer drop-off sites.
• Collected containers are shredded, chemically decontaminated, and melted into industrial-grade plastic pellets used exclusively for manufacturing non-consumer goods, such as corrugated agricultural drainage pipe, highway signposts, fence posts, and industrial pallets.

3. Sanitary Landfill Disposal

If container recycling is unavailable in the applicator's geographic area, properly triple-rinsed/pressure-rinsed and punctured containers may be disposed of as standard municipal solid waste in a state-permitted sanitary landfill.

4. Strict Statutory Ban on Open Burning in Missouri

[!WARNING] Missouri Open Burning Prohibition: Under Missouri Air Conservation Commission regulations (10 CSR 10-6.045) and the Missouri Pesticide Use Act, the open burning of pesticide containers, packaging, and chemical bags is STRICTLY ILLEGAL. Open combustion of agricultural plastics produces dense clouds of highly toxic dioxins, furans, phosgene, hydrogen cyanide, and vaporized pesticide active ingredients that cause acute human respiratory toxicity, contaminate nearby crops, and trigger severe state environmental civil penalties.