Taking care of equipment
Cross-contamination can be avoided by means of several procedures. Sampling activities for example, shall be performed, as long as possible, following a sequence from likely least contaminated to most contaminated points. Furthermore, field staff shall be informed about the origin and state of all employed equipments or tools, and the use of new and one-time use components should be encouraged as far as it is technically and economically feasible.
Non-disposable sampling devices shall be decontaminated before reusing them in the same sampling campaign or between borehole drillings, and in any case at the end of field works. These devices, for example, include electric water-level probes, floating-probes, filters, purging equipment for monitoring wells, probes of portable measurement devices (pH meters, conductivity meters, etc.), sampling tubes, water pumps, augers, etc.
After every measurement, electric (water level measurement) and floating probes (detection and depth measurement of liquid waste) shall be cleaned by the use of acetone-soaked paper, deionized water and soap. In general, paper, acetone (or other organic desorption agents), deionized water and soap must be always available in order to clean contaminated tools. In the case of sampling activities, disposable one-use bailers will be used. During manipulation of samples, especially when transferring into sample bags a protective bucket will be used in order to avoid dumping above the ground. Once sampling activities have concluded the bucket will also be cleaned with paper, acetone, deionized water and soap.
Drilling equipment exposed to hazardous substances will be cleaned before starting with a new borehole drilling. However, before cleaning, perforation tools will be kept in an empty container close to the perforation machine in order to avoid any possible dumping above the ground.
Generally, all equipments and tools used during field works will be stored appropriately in order to avoid contamination. Hence, the working equipments used during a campaign will not be stored with clean equipments if the used ones have not been previously decontaminated.
The manipulation of working equipments and tools will be only allowed to workers trained on general contamination prevention procedures.
With the aim of cleaning equipments and instruments which have come into contact with potentially contaminated soil a washing and cleaning area can be predesignated, prepared and conditioned in the study site. Therefore, after works have been completed, contaminated equipments and tools will be carried by truck on plastic layers from drilling locations to the washing area. Decontamination will be performed prior to and after each use of a piece of equipment.
The equipments will be unloaded and cleaned with water and pressurized water in the decontamination area. Once cleaning operations have been finished and working tools have been removed, decontamination water and possible liquid waste have to be correctly collected and transferred to a decantation tank (separation of liquid waste from contaminated water) and to a water treatment plant. Just in case decontamination water presents a low level of contamination, it might be incorporated into a sewage system.
As a general procedure in order to decontaminate used equipment and tools it is recommended to follow the next step:
- Cleaning of instruments with a non-phosphate detergent solution. Inside parts mechanisms and tubes of the equipments will be cleaned by means of circulating this solution through them.
- Careful rinsing with non contaminated water (tap-water or bottled water) using a brush if necessary.
- Due to presence of organic compounds, instruments can be also rinsed with an organic desorption agent (acetone, methanol, hexane, etc.). In any case, it is necessary to ask a specialized laboratory for possible interferences in subsequent analytical determinations and ask for recommendations on desorption agents.
- Careful rinsing with non contaminated water (tap-water or bottled water)
- Rinsing with deionized/distilled water
- Open-air drying before reuse
- Storing in air-tight containers or wrapping of equipment and instruments with clean plastic sheets
Finally, and in order to avoid contamination due to transmission by truck wheels, washing devices might be considered in the access area to the investigation site. These systems will avoid contamination spread outside the contaminated area.