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In many construction projects, the recyclability of the excavated soil under environmental and waste law presents our customers with recurring challenges. As an expert's office, we are interested in supporting our clients in preparing the construction site logistics and the course of the construction project in a time-optimised and cost-effective manner. In this way, valuable resources can be conserved.
We have had good experience with examining the soil excavated during a construction project in advance by means of grid field sampling, a form of in-situ sampling method.
Excavation allows for a larger area to be sampled than pile driving, as more material is available for sampling, which allows for a representative characterisation of the material.
To the planning a grid field sampling the total amount of excavated material is determined from the size of the construction site and the final excavation depth. Then the construction field is divided into a grid. The grid fields should have a reasonable size: Provided that the history of use does not show any contamination of the construction field, a quantity of max. 250 m³ per field is manageable. The fields should have a depth metre and the corresponding edge lengths.
Another advantage for the customer is the foreseeable time frame until the results are available, as the laboratory processing times are requested in advance and included in the calculation.
A grid sampling is carried out by dividing the construction field on site into permanently marked grid fields. One to two excavator trenches are laid in each grid field. For each depth metre, the required number of composite samples is compiled and sent to the laboratory. Documentation is carried out by means of meaningful photos of the excavated material and the trenches. Indispensable for this are a measuring rod, prepared signs and the corresponding sampling protocols.
Care must be taken to excavate the soil material by the metre and store it to the side of the trench for sampling. When re-sealing the trenches, the material must be dredged back in the original order to avoid carry-over of contamination.
Grid field sampling is useful for a construction project if the terrain to be investigated is suitable for this type of investigation. This is true, ...
- If a large amount of excavated soil is to be expected in a short time.
- if the soil material to be excavated consists to a large extent of anthropogenic fills
- if the building site has a history of previous use, e.g. is located in the inner city or in a (former) industrial area and certain contamination is to be expected as a result, but no contaminated site is present.
- if a waste law certificate is required for the excavated material because it cannot be used on the construction site for terrain modelling. This case occurs if, for example, it is unsuitable from a geotechnical or recycling law point of view or simply too much, or if the excavated soil cannot be stored as a heap on the construction site logistically due to a lack of space or due to the construction period.
It goes without saying that we take all legal principles into account when carrying out grid field sampling, including, for example, the following laws, ordinances and regulations:
- Recycling and Waste Management Act
- BBodSchV
- Landfill Ordinance
- LAGA M 20
- LAGA PN 98
- VwV (exemplary for country-specific regulations)