Clean vs. Dirty: knowing how to do the right thing in urban redevelopment
What is Urban Fill?
There are numerous Federal, State, and local definitions for urban or historic fill depending on the property location and regulatory program governing the site.
The USDA’s Natural Resource Conservation Service (NRCS), which is responsible for classifying and mapping US soils, states that soils in urban areas can be divided into two general types: “natural soils,” which formed in material naturally deposited or weathered from the underlying bedrock, and “anthropogenic soils,” (i.e., man-made), which formed in human-deposited material or fill. The NRCS cites the following examples of fill material in urban soils:
- Natural soil materials that have been moved around by humans
- Construction debris
- Materials dredged from waterways
- Coal ash
- Municipal solid waste
- A combination of any or all of the above
The NRCS does not comment on specific contaminants in urban soil; however, it is important to recognize that “debris” may also include materials from demolition of fire damaged structures. Similar to coal ash and other kinds of ash, these types of materials typically include polycyclic aromatic hydrocarbons (PAHs), which are semi-volatile organic compounds that are the product of incomplete combustion. Although specific contaminants are subsequently discussed in more detail in this paper, this is noteworthy since all of the following definitions reference ash and/or PAHs (also sometimes referred to as polynuclear aromatic hydrocarbons).