Prior to sampling, what must be done to the surface soil?

The correct procedure prior to sampling soil is to rapidly scrape away 3 inches of soil. This action is crucial for several reasons. First, the top layer of soil often contains organic matter, debris, or contaminants that can skew test results. By removing the surface layer, you are obtaining a sample that is more representative of the subsurface soil, which is where many contaminants are most commonly found, especially in the context of heating oil tanks.

Scraping away this layer helps to ensure that the sampling is conducted on a clean and uncontaminated surface, allowing for accurate analysis of the underlying soil layers. This procedure is often standard in soil sampling practices, particularly in environmental assessments related to potential contamination from heating oil or other hazardous materials.

In contrast, the other options do not adequately prepare the sampling site for accurate analysis. Leaving the surface undisturbed might include unwanted organic or contaminant material, while covering the area with protective material does not facilitate sampling and can hinder access to the soil. Marking the area with flags serves no purpose in preparing soil for sampling and does not affect the integrity of the sample taken.