C.2.5 Subsampling Procedures

Photograph of the subsampling process.

Figure C.2-6. Photograph of the subsampling process.

Tools and Materials

  • 10 sieve
  • stainless steel trays lined with aluminum foil
  • stainless steel spatula
  • 4-ounce amber sample jars
  • bench scale
  • wire brush
  • liquid soap
  • 12-inch ruler
  • disposable latex sampling gloves
  • notebook and digital camera

Subsampling was conducted in the Department of Transportation and Public Facilities Materials Lab in Juneau, as shown in Figure C.2-6. Six subsamples were collected, including a duplicate for each of the three subsamples for an additional comparative metric.

Bulk samples were sieved to 2 mm using a #10 sieve. Following an initial attempt at sieving the wet soil (sample HWL 1-1), the bulk samples were placed on trays and dried at room temperature for 30 hours prior to subsampling.

Before sieving, the bulk soil samples each weighed approximately 1.8 kg. Less than half of the bulk sample was removed during the sieving process, leaving approximately 1 kg of soil for use during subsampling.

Sieved soil was spread onto a foil-lined tray with dimensions of about 7 × 10 × 3/8 inches thick. The soil was then evenly divided into a 30-square grid. About 1.5 g was collected from a minimum of two locations in each square using a small spatula to ensure that fine particles were not missed.

The 30 subsample increments, weighing approximately 45 g total, were placed in a labeled, wide-mouth sample jar placed on a bench scale. The process was repeated for the remaining two bulk samples and their duplicates; the spatula was cleaned with soap and water between each bulk subsampling event.