The survey unit sizes in MARSSIM are not intended to be prescriptive. However, MARSSIM does offer one possible set of survey unit sizes, primarily as an example. For Class 1 survey units, MARSSIM suggests survey unit sizes of 100 m2 for structures and 2,000 m2 for land areas. For Class 2 survey units, MARSSIM suggests survey unit sizes between 100 and 1,000 m2 for structures, and between 2,000 and 10,000 m2 for land areas. However, these survey unit sizes are not intended to be prescriptive. For Class 3 survey units, MARSSIM does not suggest a limit for either structure or land areas. Section 4.6 of MARSSIM Chapter 4: Preliminary Survey Considerations recommends limiting survey units based on classification, exposure pathway modeling assumptions, and site-specific conditions.
For more information on the MARSSIM process, visit MARSSIM on EPA.gov.