C.2.4 Field Sampling Procedures

Tools and Material

  • Internet random number generator
  • garden shovel
  • 20-penny galvanized nails
  • hand spade
  • stainless steel spoons
  • 2-gal zip-lock bags
  • colored nylon twine
  • 50-foot flexible tape
  • 12-foot tape
  • stainless steel ruler
  • hand calculator
  • leather gloves
  • disposable latex sampling gloves
  • field notebook
  • digital camera

Although the edges of the stockpile were not clearly delineated, the stockpile dimensions measured approximately 33 × 13 × 1 feet deep. A 30-cell grid (10 cells long, 3 wide) was constructed using 20-penny nails for stakes and colored twine to form the grid pattern. Each cell measured approximately 40 inches long × 52 inches wide (see Figure C.2-2.).

21 22 23 24 25 26 27 28 29 30
11 12 13 14 15 16 17 18 19 20
1 2 3 4 5 6 7 8 9 10

Overall dimensions: 33 x 13 feet
Individual cell dimensions: 52 x 40 inches
Depth: 12 inches

Arrow up Pointing North

Design and construction of the grid.

Figure C.2-2. Design and construction of the grid

Random planar and depth coordinates were determined after the cell dimensions were established using an online random number generator. Thirty length coordinates were determined by setting the minimum and maximum numbers in the random number generator between 0 and 40. Thirty width coordinates were determined by setting the minimum and maximum numbers between 0 and 52. Thirty depth coordinates were determined by setting the minimum and maximum numbers between 6 and 12. This method ensured that the top 6 inches of soil would not be sampled, as dictated by the MI sampling guidance.

Sampling locations were determined by assigning X- and Y-axes to the grid. Length was measured along the X-axis beginning at the southwest corner of the cell, followed by a Y-axis, or perpendicular measurement, to determine the width coordinate. A 20-penny nail was pushed into the soil at each coordinate to establish the primary sampling location. For example, the random coordinates for cell #2 were 33 inches along the length (X-axis) and then 18 inches to the north (Y-axis). Beginning at the southwest corner of each cell, this process was repeated until the 30 primary sampling locations were established.

A garden shovel was used to dig the holes to the approximate depth once all planar coordinates were determined. A small hand spade and 12-inch ruler were used to obtain the exact depth at each location and to clean away any soil that may have sloughed from the sidewalls.

Depiction of the primary, duplicate, and triplicate increments

Figure C.2-3. Depiction of the primary, duplicate, and triplicate increments

Using a stainless steel spoon, three tablespoons of soil (~60 g per increment) were collected from the proper depth at each location and placed in zip-lock bags. If the hole was overexcavated, the sample was taken from the sidewall at the proper depth. This process was repeated until all 30 primary bulk sample increments were collected.

Duplicate and triplicate bulk samples were collected at the same depth as the primary sample within each cell using the procedures described in Figure C.2-3. Sample locations were determined by stepping out approximately one-half the distance of the cell length and width from the primary sample hole. The step-out direction varied depending on the location of the primary sample hole within the cell. For example, if the primary hole was near the far corner to the right, as shown by Figure C.2-3, step-out directions were to the left (duplicate) or down (triplicate). This method ensured an independent and systematic random approach within each cell.

Bulk soil samples, weighing approximately 1.8 kg each, were doubled-bagged, sealed, and taped for shipment (see Figure C.2-4). Samples were not cooled because transit time back to Juneau was minimal. After the samples arrived in Juneau, they were refrigerated until the time of subsampling (see Figure C.2-5).

Photograph showing increment collection

Figure C.2-4. Photograph showing increment collection.

Photograph of soil sifted through a #10 sieve.

Figure C.2-5. Photograph of soil sifted through a #10 sieve.