Remediation: Techniques and Cost - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 378

The most common cause of remediation failure is the improper characterization of the
site. Not identifying a source of contamination, underestimating contaminant mass, not
identifying a complete list of contaminants of concern, executing an incomplete sampling
plan, or improper sampling techniques and methods can lead to remediation being unsuc-
cessful and result in increased cost, time, and effort to achieve the remedial objective.
Other causes for remediation failure include technology misapplication and design, envi-
ronmental changes such as a change in groundwater flow direction, sudden change in
local climatic conditions such as a drought or flood, changes in geochemistry, and addi-
tional releases.
Some of the factors controlling or influencing the extent of the remediation required
include
• Contaminant or contaminants released
• Concentration
• Nature and extent
• Media impacted (air, surface water, groundwater, soil, sediment)
• Geology
• Hydrogeology
• Hydrology
• Location
• Potential receptors
• Land use
• Future land use
• Climate
• Time necessary to achieve objective(s)
• Results of risk assessment and feasibility study
• Cost
Driven by the need for more effective and less costly cleanup costs, new technologies are
constantly being developed to remediate contaminated soil and groundwater. Over the
past several decades, approximately 2000 new remedial technologies for environmental
contamination have emerged (USEPA 1995, 2007). The impetus for these new technologies
includes (1) ineffectiveness of early remedial methods, (2) excessive cost of early meth-
ods, and (3) regulatory goals requiring remediation to standard-based levels that in many
instances were to pristine pre-contaminant or background conditions.
In the mid-1990s, there was a transition from the standard-based remediation cleanup
goals toward risk-based cleanup goals (ASTM 1995). Remediating a site to risk-based cri-
teria involves calculating site-specific cleanup levels based on the risks posed by the pres-
ence of specific contaminants. This process incorporates (1) the toxicity and nature of each
contaminant, (2) the site's geological and hydrogeological setting, (3) fate and transport
mechanisms, (4) future land use, and (5) analysis of potential receptors. In most cases,
applying risk-based cleanup goals translated into lower amounts of contaminant remedia-
tion to achieve closure for a specific contaminant at a particular site, and this guideline
lowered the cost and time required to remediate a site (USEPA 2002).
The overview of the most commonly available remedial technologies begins with a
description of the methods used to remediate contaminated soil.