5.3.3 Stockpile ISM Samples

Special considerations for selecting DUs during the systematic planning process for sampling soil stockpiles include the following:

  • the source of the soil in the stockpile
  • how the stockpile was created (over time, if applicable)
  • how best to access the pile for sampling, (e.g., large or unstable)
  • contaminants targeted for lab analyses

One of the best options is to coordinate sampling with the formation of any stockpiles on the site. When the stockpile is being formed, there is generally good access to sampling each portion of the pile over time, and ensuring access to the entire stockpile DU is provided for good sample representativeness. If an existing stockpile is relatively small, good options may include moving the the pile and collecting the increments while it is being moved (e.g., from the front-end loader buckets, at appropriate intervals), or flattening or spreading out the stockpile sufficiently so that it is safely accessible to sample with a hand coring or other device. If the stockpile is very large or unstable, all available sampling tools or methods that safely provide access should be considered, with the goal of coming as close as possible to collecting a minimum of 30 systematic random or random within grids increments throughout the stockpile (both vertical and horizontal locations). Replicates are important to evaluate the precision of stockpile sampling and should be collected similarly to the original sample except in separate random locations. Large stockpiles could be divided or segregated into separate DUs (see Figure 3-10), especially a specific portion or volume of the stockpile will be used in a manner that will become the primary exposure unit of concern in the future (e.g., certain portions or volumes of the stockpile will be hauled to residential lots as surface fill for backyards). A resource for additional information on ISM approaches for soil stockpile sampling is the Hawaii Department of Health (HDOH) Technical Guidance Manual (HDOH 2008b).

Refer to Section 3.3.8 of this document for additional information on ISM sampling of stockpiles.