Urbanization and the Geoenvironment - Sustainable Practices in Geoenvironmental Engineering - page 256

Buried structures

Yes

Recycling and reuse of
materials

Can be extracted?

No

Yes

Remediation must
meet regulatory
requirements

Is it hazardous?

No

Artificial
diagenesis to
stabilize ( see
Chapter 12 )

Yes

Is it a hollow structure

Structure
required
programs

No

Convert to
parking lot or
park area

Yes No

Can it be integrated into
planning?

FIGURE 7.17
Schematic protocol for managing underground structures in a redevelopment plan. (With kind permission
from Springer Science+Business Media: Urban Land, Degradation, Investigation and Remediation , 2003, 331 pp.,
Genske, D.D.)

In the provinces of Québec and Ontario, treatment centers for contaminated soil serve
various clients including real estate developers (for example, conversion of a gas station to
condos), excavation contractors, environmental consultants, government agencies, indus-
tries, and manufacturing companies. The process is an in situ biopile that uses microor-
ganism to breakdown the contaminants while controlling aeration, humidity, and nutrient
levels. The process is shown in Figure 7.18. Treated contaminants include petroleum
hydrocarbons, volatile organic contaminants, PAHs, PCP, creosote, and phenol. Water and
air emissions from the process can also be treated biologically via an aerated wastewater
treatment system, wetlands, and a bioilter. Depending on the remaining contaminant lev-
els, the treated soil may be able to be returned to the original site.
Regardless of the origin of the contaminants in the area, an evaluation of the threats to
human health and the environment must be undertaken before the remediation process.
Both the potential exposure time and level must be considered. Figure 7.19 gives a low-
chart that illustrates a simple procedure for evaluation and treatment. Techniques such
as selective sequential extraction are useful in determining the likelihood that the heavy
metals are mobile. Selective sequential extraction studies were performed on nine soil
samples (Huang, 2005). Figure 7.20a and b shows the results for lead and zinc, respec-
tively. It can be seen that both lead and zinc have different afinities toward different soil
fractions. Both Pb and Zn have higher afinities toward the soil fractions of organic mat-
ter and oxides. Only a small fraction of both metals is associated with the exchangeable