Department of Health Seal

TGM for the Implementation of the Hawai'i State Contingency Plan
Section 5.9


Figure 5-51. Triple Wash Decontamination of Sampling Equipment

Decontaminate sampling devices used to collect samples prior to use and between DUs. This includes drill rods and coring used for the collection of subsurface increments and samples. Decontamination of sampling equipment during the collection of increments within a DU for preparation of a bulk Multi Increment sample is not necessary. This includes the collection of samples or subsamples for the same DU layer, when multiple DU layers and core increments are being sampled (e.g. subsurface borings). Decontamination of equipment between DU replicates samples is recommended, since replicates are intended to be completely independent.

Protect decontaminated equipment from incidental contact with potential contaminant sources by placing in sealed plastic bags or otherwise keeping the equipment well covered.

The following, triple-wash approach is recommended as a default procedure for decontamination of sampling equipment where trace levels of contaminants are being investigated (Figure 5-51).

  1. Removed caked soil and debris from sampling equipment by hand;
  2. Wash with light detergent;
  3. Rinse with tap-water;
  4. Rinse a second time with tap-water.

The use of solvents to clean equipment should be avoided in order to minimize the generation of potential hazardous waste (see Section 5 & USEPA 2015). Document the decontamination procedure in the SAP and the final investigation report. These procedures may not be adequate for decontamination of equipment used to collect water samples (refer to Section 6). Carry multiple sets of sampling tools in order to expedite sample collection and allow decontamination of equipment in batches, ideally just once a day at the start or end of a sampling day.

Heavy equipment parts necessary for the advancement of any sampling device must be steam cleaned or high pressure/hot water washed between DU locations. Examples of these types of equipment include auger flights, drill rods, and backhoe buckets.

The collection of soil samples beneath concrete pads, floors, or asphalt paved areas may sometimes be necessary. If the equipment used to remove the concrete or asphalt has the potential to come into direct contact with the underlying soil, it must also be decontaminated. Decontaminate this equipment prior to and between sample locations in a manner similar to decontamination procedures discussed above for heavy equipment.

The collection and testing of equipment rinsate samples is not required or necessary for typical soil investigations. The practice is designed for "ultraclean" sampling approaches most typically associated with the collection of water samples, where parts-per-trillion level accuracy of laboratory data is desired. The collection of large Multi Increment soil (and sediment) samples also minimizes the potential for cross contamination of samples if small amounts of soil are inadvertently left on sampling tools, provided that the basic decontamination procedures described above are followed.