How many inches of soil should be scraped off before sampling?

Scraping off 3 inches of soil before sampling is essential to ensure that the sample collected accurately reflects the condition of the subsurface soil without contamination from organic material, debris, or any surface residues. This depth helps to minimize the impact of surface factors that may not be representative of the underlying soil environment, particularly in situations where hydrocarbon contamination may have occurred.

By removing 3 inches, you are increasing the likelihood that the sample will present a clearer picture of the soil's true characteristics and any potential contamination that lies at or below that depth. In environmental assessments, maintaining the integrity of soil samples is crucial for reliable testing results and subsequent remediation efforts.